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Kearney, Theresa Elizabeth. "Survival of pathogenic bacteria in anaerobic digesters." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334706.
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Collins, Cathleen A. "Ubiquitin in host defense against pathogenic mycobacteria." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3359543.
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Oki, Aminat. "Characterization of the Effects of Iron on Neisseria Gonorrhoeae Surface Protein Modulation and Host Cell Interactions." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3534.
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Iron is an essential nutrient that is sequestered by iron-binding proteins in the human host resulting in a hostile environment for microbes. Neisseria gonorrhoeae, however, can utilize numerous iron-binding proteins such as transferrin and lactoferrin to acquire this nutrient. During initial infection, gonococci have access to transferrin and lactoferrin present in semen and vaginal fluids, as well as to hemoglobin present in blood during menses or disseminated infections. Consequently, the gonococcus likely encounters conditions of high iron at some stages in the course of natural infection. Potential contributions of iron to gonococcal invasion have however been largely over looked in the field as most studies investigating invasion represent iron depleted environments. Considering the link between menses in women and ascending gonococcal infections, we hypothesized that high iron concentrations present at this time triggers the induction of membrane proteins that enhance gonococcal pathogenesis. Here, we report the gonococcal iron-induced surface proteome and show evidence of post-translational modification of many of these proteins. We also present evidence of an iron enhanced, Opa-independent invasion mechanism. Finally, we investigated the role of NspA, TdfJ and NGO1063 on Opa-independent iron induced invasion. Our studies underscore the importance of investigating the effect of iron on gonococcal host cell interactions. Given the potential clinical relevancy of this phenomenon, data from our studies represent a solid framework for further investigation of gonococcal pathogenesis.
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Toney, Denise Marie. "Mechanisms of Complement Resistance by Pathogenic Naegleria fowleri Amoebae." VCU Scholars Compass, 1993. http://scholarscompass.vcu.edu/etd/5063.
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The genus Naegleria is composed of a distinct group of free-living amoeboflagellates that include both pathogenic and nonpathogenic species. N. fowleri, the only pathogenic species of Naegleria to be isolated from humans, is the etiological agent of primary amoebic meningoencephalitis, a rare but rapidly fatal disease of the central nervous system in humans and in laboratory animals. The mechanisms of pathogenicity and the determinants of virulence of N. fowleri are unknown. Both pathogenic and nonpathogenic Naegleria activate the alternative complement pathway, however pathogenic N. fowleri are complement-resistant and nonpathogenic N. gruberi are complement-sensitive. The ability to resist complement-mediated lysis may be an important determinant of virulence of N. fowleri. These studies demonstrate that pathogenic N. fowleri possess at least two mechanisms for resisting complement lysis. Pathogenic N. fowleri synthesize a surface associated protein which appears to possess structural as well as functional homology to the human complement regulatory glycoprotein, CD59. Also, other surface glycoproteins appear to play a role in regulating complement lysis either directly or by indirect inhibitory mechanisms. In addition to complement regulatory glycoproteins, pathogenic N. fowleri possess the ability to remove membrane deposited complement proteins, C5b-C9, from their cell surface by membrane vesiculation. The presence of complement regulatory proteins and the ability to vesiculate in response to serum complement, alone or in combination, serves to protect pathogenic N. fowleri from complement-mediated damage. Nonpathogenic N. gruberi do not appear to possess surface complement regulatory proteins or the ability to vesiculate in response to serum complement. Additional studies demonstrate that growth medium modulates complement resistance and virulence. More importantly, by using changes in growth medium, an in vitro model was developed for differentially expressing proteins associated with the complement-resistant state. The induction of these de novo synthesized proteins may serve as markers of virulence and complement resistance in pathogenic N. fowleri amoebae.
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Burda, Whittney. "Exploring the Pathogenic and Drug Resistance Mechanisms of Staphylococcus aureus." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5650.
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We have previously identified σS, an ECF sigma factor that is important in the virulence and stress response of S. aureus. Transcriptional profiling of sigS revealed that it is differentially regulated in a variety of laboratory and clinical strains of S. aureus, suggesting that there exists a regulatory network that modulates its expression. In order to identify direct regulators of sigS expression, we performed a biotin pull down assay in tandem with mass spectrometry. We identified CymR as a direct regulator and observed that sigS expression is increased in cells lacking cymR. In addition, transposon mutagenesis was performed to identify regulators of sigS expression. We identified insertions in genes that are transcriptional regulators, and elements involved in amino acid biosynthesis and DNA replication, recombination and repair as influencing sigS expression. Finally, methyl nitro-nitrosoguanidine mutagenesis in conjunction with whole genome sequencing was employed and revealed mutations in the lactose repressor, lacR, and the membrane sensor histidine kinase, kdpD, as negatively effecting sigS expression. EMSAs revealed that LacR is an indirect regulator of sigS expression, while the response regulator KdpE is a direct repressor. These results indicate that a complex regulatory network is in place for sigS that modulates its expression.
In a continuation of studies on σS regulation, we next explored interplay with the products of genes conserved within the sigS locus. We determined that this region is conserved amongst all the sequenced staphylococci, and includes four genes: SAUSA300_1721 (a conserved hypothetical protein), as well as sigS, ecfX, and ecfY. In order to investigate the relationship between EcfX and σS we performed protein pull down assays and observed that these two protein interact. Further to this, transcriptional analysis of sigS in an ecfX mutant reveal that expression of sigS is decreased, indicating that it is an activator. Architectural analysis of the sigS locus via RNAseq revealed that the majority of transcription in this region comes from ecfY, a gene that is downstream and divergent to sigS. We demonstrate that inactivation of ecfY leads to a significant increase in sigS expression, and that ecfY null strains are more resistant to DNA damaging agents such as UV, H2O2, MMS, and ethidium bromide, which we have previously demonstrated that a sigS mutant is highly sensitive to. Our studies also revealed that an ecfY null strain is better able to survive intracellularly following phagocytosis by RAW 264.7 cell and demonstrates increased survival in whole-human blood, which is again opposed to that previously observed for sigS deficient strains. Because the ecfY null strain overexpresses sigS, we investigated the regulon of this sigma factor using this mutant in conjunction with RNAseq analysis. We identified that genes putatively under the control of σS are involved in DNA damage and repair, virulence, amino acid starvation and nucleic acid biosynthesis. Collectively, our results indicate that σS is regulated via a unique mechanism: positively through an apparent need for an activator protein (EcfX) and negatively via RNA-RNA interaction (the 3’ UTR of ecfY). We suggest that the evidence presented here greatly adds not only to our understanding of the regulatory circuits extant within S. aureus, but also to alternative sigma factor biology in general.
Finally, we evaluated the efficacy of a novel library of quinazoline-based compounds against a highly drug resistant strain of S. aureus. We performed structure activity and structure property relationship assays in order to identify lead compounds. These methods lead to the identification of N2,N4-disubstituted quinazoline-2,4-diamines that had low minimum inhibitory concentrations, along with favorable physiochemical properties. Evaluation of their biological activity demonstrated limited potential for resistance of to our quinazoline based compounds, low toxicity to human epithelial cells, and strong efficacy in vivo. Taken together, our findings support the use of quinazoline derivatives as potential new antimicrobials against multidrug resistant S. aureus.
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Islam, Shahidul Md. "Studies on gene expression in a pathogenic bacterium." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1729/.
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The activity of the major pathogenicity determinant of enterohaemorrhagic Escherichia coli is primarily coordinated by expression of the LEE1 operon which is part of the locus of enterocyte effacement (LEE). The LEE1 operon regulatory region has been dissected. LEE-encoded transcription factor, GrlA, activates the LEE1 P1 promoter by binding to a target located within the 18 base pair spacer between the promoter 10 and 35 elements. Shortening this spacer to 17 base pairs increases P1 promoter activity and short-circuits GrlA dependent activation, suggesting that GrlA functions like MerR family transcription activators. It was also found that the LEE1 P1 promoter is overlapped by a cryptic promoter, designated P1A. A single base substitution in the P1 consensus -35 element unmasks P1A promoter activity. In contrast, P1A activity is much less when P1 is inactivated by a mutation in its -10 hexamer element. Hence, even when P1 is inactive, the consensus -35 element sequesters RNA polymerase and prevents its access to the P1A promoter. The LEE1 leader sequence also contains a mini-gene that encodes a dipeptide. Genetic studies showed that expression of this mini-gene is important for optimal expression of downstream genes.
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Brownell, Abigael C. "The Roles of Microcystin and Sulfide in Physiology and Tactic Responses of Pathogenic and Non-Pathogenic Mat-Forming Cyanobacteria." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1364.
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Planktothricoides raciborskii and Roseofilum reptotaenium are physiologically similar, yet ecologically distinct organisms found in a hot spring outflow and coral black band disease (BBD), respectively. The aim of this study was to elucidate the relationship between R. reptotaenium and sulfide in BBD, to compare microcystin (MC) production in response to environmental factors, and to determine chemotactic responses to MC and sulfide by the two organisms. Results showed that the pathogenicity of R. reptotaenium in BBD is dependent on sulfate-reducing bacteria as secondary pathogens. Roseofilum reptotaenium produced significantly more MC than P. raciborskii, as measured using ELISA. Roseofilum reptotaenium was negatively chemotactic to sulfide, determined using horizontal and vertical gradients in agar, while P. raciborskii was not affected. Neither cyanobacterium was chemotactic to MC in the agar assays. The ecophysiology of P. raciborskii and R. reptotaenium in relation to MC production and response to sulfide reflected their pathogenic versus non-pathogenic status.
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West, Patrick William John. "Studies on the identification and pathogenic potential of Streptococcus mitis." Thesis, University of Salford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308265.
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Cockburn, Chelsea. "Acid sphingomyelinase is essential for vacuolar development of A. phagocytophilum." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5684.
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Obligate intracellular bacteria are significant causes of morbidity and mortality with over two hundred and fifty million infections worldwide annually. One such bacterium, Anaplasma phagocytophilum is the etiologic agent of human granulocytic anaplasmosis (HGA), a tick-transmitted febrile illness. Previous studies have shown that A. phagocytophilum lacks genes for cholesterol biosynthesis and solely relies on Niemann Pick protein type C (NPC)1-mediated low density lipoprotein (LDL)-derived cholesterol to complete its infection cycle.Acid sphingomyelinase (ASMase) is a lysosomal enzyme that is essential for diverse cellular processes including liberation of LDL-derived cholesterol from the lysosome. By first studying A. phagocytophilum, we found that functional inhibitors of acid sphinogmyelinase (FIASMAs) arrest the bacterium’s infection cycle in a dose-dependent manner. FIASMAs inhibit vacuole maturation, conversion to the infectious form, and eliminate the production of infectious progeny. NPC1-mediated LDL-derived cholesterol traffic to the ApV is abrogated in the presence of FIASMAs. Similar to the in vitro model, A. phagocytophilum cannot establish a productive infection in both ASMase-/-and FIASMA treated mice. Furthermore, we extended our studies to Coxiella burnetti (Q fever), and Chlamydia spp. (STD, infectious blindness, pneumonia). FIASMA treatment has a rapid bacteriocidal effect on C. burnettiwithin host cells. Additionally, FIASMA treatment inhibits C. trachomatis and C. pneumoniae inclusion expansion and infectious progeny generation, with C. pneumoniae being more severely impacted. These data highlight the critical, yet distinct roles that ASMase plays in these pathogens’ infection cycles. Furthermore, these results signify the therapeutic potential of FIASMAs for treating diseases caused by these pathogens.
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Holmes, Ashleigh. "Characterising virulence factors from pathogenic bacteria using fluorescent reporters." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3317/.
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Protein translocation systems are invaluable to pathogenic bacteria, facilitating the display of virulence factors on their surface or their release into the extracellular environment. Some protein export systems are ubiquitous and essential to cell survival whereas others are horizontally acquired on prophages or pathogenicity islands (PAI), in many cases providing the bacterium with pathogenic advantages. For the majority of the known protein export systems, their structure, function and secreted substrates have been characterised, yet some proteins have been identified that are secreted via unknown mechanisms. Enterohaemorrhagic Escherichia coli (EHEC) O157:H7 is an important cause of human foodborne disease worldwide. The pathogenesis of this bacterium is mainly attributed to the secretion of toxins and the presence of a Type III Secretion System (T3SS). The T3SS can translocate bacterial proteins, known as effectors, into the host cell which mediate an effect culminating in the formation of a characteristic attaching and effacing (A/E) lesion. This system is encoded on a horizontally acquired PAI termed the locus of enterocyte effacement (LEE). The LEE not only encodes the T3SS apparatus but also several effectors secreted by the system and transcription factors which regulate its expression. However, it was recently found that T3SS not only secretes LEE encoded effectors but can also secrete proteins encoded on other prophages present in the EHEC genome. Characterisation of these non-LEE encoded effectors is ongoing and this study investigates the expression, regulation and function of non-LEE encoded effector H1 (NleH1) and H2 (NleH2). NleH1 and NleH2 are secreted by the T3SS but are encoded on different prophages. This study demonstrates that expression of NleH1 and NleH2 is induced in the same in vitro conditions which stimulate the expression of the LEE but is diminished upon initial host cell contact in vitro. Transcription of nleH1 and nleH2 is dependant upon factors specific to E. coli O157:H7 and these factors are regulated by LEE encoded regulators Ler and GrlA, as they have a positive effect on nleH transcription. NleH1 and H2 are predicted serine/threonine protein kinases and are able to autophosphorylate. Yeast two hybrid screening and 2D differential gel electrophoresis did not elucidate a eukaryotic protein binding partner of NleH1 or NleH2. Transfection assays show that they do not have a significant effect upon NF-κB activation in vitro. Determining the expression, regulation and function of non-LEE encoded effectors contributes towards further understanding of how this pathogen causes disease. Streptococcus pneumoniae, also known as the pneumococcus, is another globally important human pathogen. It is a very diverse pathogen, with over 90 capsular serotypes and is naturally competent for DNA uptake. Pneumococcal pathogenesis is facilitated by the production of a pore-forming toxin, pneumolysin. Pneumolysin’s activities in pneumococcal pathogenesis extend beyond its cytolytic function as it can also activate the complement pathway and modulate the host cytoskeleton. Pneumolysin is a member of a conserved family of toxins known as the cholesterol dependant cytolysins but differs due to the lack of a secretion signal peptide within its sequence. This indicates that it is not secreted from the bacterium however it has been reported that some strains can release pneumolysin in a cell lysis-independent manner. Additional to this, pneumolysin can also localise to the cell wall, and this localisation is not strain dependent. This study characterised codon-optimised N-terminally labelled pneumolysin constructs and applied them to assess the localisation of pneumolysin. In addition, the importance of autolysin and genes which are co-transcribed with Ply upon the localisation/secretion of pneumolysin was investigated by construction of a pneumococcal strain carrying an autolysin-pneumolysin fusion which naturally occurs in equine strains. These genes were not required for the translocation of pneumolysin or its association with the cell wall. Growth of this strain, and its isogenic parent, in vitro at a low density and low temperature resulted in the pneumolysin being detected in the broth culture. This indicates that pneumolysin can be released from the cell wall and that this action is not dependant upon the genes which were deleted in the mutant. The distribution of pneumolysin on the pneumococcal surface was assessed with immunofluorescence, and LumioTM substrate fluorescence, microscopy and found to have a general distribution. As a contribution to future pneumococcal research, codon-optimised fluorescent protein reagents were developed and can be used as reporters for gene expression and protein localisation.
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VieBrock, Lauren. "ORIENTIA TSUTSUGAMUSHI ANKYRIN-REPEAT PROTEIN FAMILY TARGETING OF THE HOST ENDOPLASMIC RETICULUM." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/4023.
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Abstract
ORIENTIA TSUTSUGAMUSHI ANKYRIN REPEAT-PROTEIN FAMILY TARGETING OF THE HOST ENDOPLASMIC RETICULUM
By Lauren VieBrock, B.S.
A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University
Virginia Commonwealth University, 2015
Director: Jason A. Carlyon, Ph.D.
Professor
Microbiology and Immunology
Scrub typhus is an understudied, potentially fatal febrile illness, which poses threat to one billion people annually in the Asia-Pacific region. The host-pathogen interactions that facilitate the intracellular survival of the etiologic agent, Orientia tsutsugamushi, are not well understood. The Orientia tsutsugamushi genome encodes a large number of ankyrin repeat-containing proteins (Anks), key virulence factors for other intracellular pathogens, as well as components for Type I (T1SS) and Type 4 secretion systems (T4SS), commonly used to deliver them. We sought to characterize the roles of the Anks in O. tsutsugamushi infection. In this study, we demonstrated that O. tsutsugamushi expressed all 20 anks and the genes for the T1SS, for which they are substrates. Many ectopically expressed Anks displayed a tropism for the host endoplasmic reticulum (ER). These
results suggest the importance of the Anks and the ER to Orientia tsutsugamushi pathobiology.
We demonstrated that O. tsutsugamushi tightly associated with the ER and induced ER stress and defects in protein secretion of its host cells. Therefore, we hypothesized that the ER-tropic anks expressed during the initial hours of infection are critical for establishing infection and do so by interacting with specific host cell targets to modulate host cell function to benefit intracellular survival. ER-tropic Ank4 was detected as expressed early in infection and was further characterized for its contribution to the alterations of the ER during infection. Bat3 was identified as a target of Ank4, and Ank4 expression correlated with a decrease in Bat3 protein levels, induction of ER stress, and defects in protein secretion. These effects were Ank4 F-box dependent, implicating polyubiquitination and proteosomal degradation of Bat3. As Ank4 colocalized with Bat3, a chaperone component of ER-associated degradation (ERAD) of misfolded proteins, ERAD function was measured in cells expressing Ank4. In an F-box dependent manner, Ank4 expression resulted in decreased degradation of a model substrate and indicated inhibition of the ERAD pathway. Similarly, we demonstrated that in O. tsutsugamushi infection, Bat3 levels were significantly reduced early in infection and ERAD degradation was inhibited. After several days of infection however, Bat3 levels and ERAD degradation had both recovered, suggesting temporal modulation of ERAD in infection. Taken together, these data suggest that O. tsutsugamushi has a large capacity to disrupt the host ER, exemplified by Ank4 mediated ERAD dysfunction by depletion of host Bat3.
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Racicot, Bergeron Catherine. "Food animal reservoir for extraintestinal pathogenic «Escherichia coli» causing human infections." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104886.
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Studies of extraintestinal infections caused by genetically related strains of Escherichia coli among unrelated people have demonstrated the epidemic potential of this group of bacteria. These related extraintestinal pathogenic E. coli (ExPEC) may have a common source. Our group recently described how retail meat, particularly chicken, may be a reservoir for ExPEC causing human urinary tract infections (UTIs). By moving upstream on the farm to fork continuum, this study tests whether the reservoir for ExPEC is in food animals themselves. A total of 824 geographically and temporally matched E. coli isolates from cecal contents of slaughtered food animals (n=349) and human UTI (n=475) sources were compared. Using 6 different typing methods, an evolutionary relationship was observed between E. coli isolates from the food animal reservoir and human UTI. Moreover, chicken was the predominant animal species from where the related isolates originated. Using an evolutionary model, chicken was determined to be the most likely source of the human UTI isolates. This study confirmed that an animal reservoir, principally in chicken, may exist for ExPEC causing community-acquired UTI.Les études portant sur les infections extra-intestinales causées par des souches d'Escherichia coli génétiquement apparentées, chez des personnes non reliées entre elles, ont démontré le potentiel épidémique de ce groupe de bactéries. Ces souches d'E. coli pathogènes extra-intestinales (ExPEC) apparentées auraient possiblement une source commune. Notre groupe a récemment décrit comment la viande de détail, plus particulièrement le poulet, pourrait être un réservoir d'ExPEC responsables d'infections urinaires (IUs) chez les humains. En se déplaçant plus en amont dans le continuum de la ferme à la fourchette, cette étude teste si le réservoir d'ExPEC se trouve dans les animaux de production eux-mêmes. Un total de 824 isolats d'E. coli de provenances géographique et temporelle communes, prélevés dans le contenu caecal d'animaux abattus (n=349) et de cas d'IU humaine (n=475) ont été comparés. Par l'utilisation de 6 différentes méthodes de typage, une relation évolutionnaire a été observée entre les isolats d'E. coli provenant du réservoir animal et d'IU humaine. De plus, le poulet était l'espèce animale prédominante parmi les isolats parentés. L'utilisation d'un modèle évolutionnaire a permis de déterminer que le poulet est la source la plus probable des isolats d'IU humaine. Cette étude a confirmé qu'un réservoir animal, principalement chez le poulet, pourrait exister pour les ExPEC qui causent des IUs acquises en communauté.
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Mabogo, Rudzani David Lesly. "The prevalence and survival of Campylobacter, Salmonella and Listeria species in poultry processing plant." Thesis, University of the Western Cape, 2004. http://etd.uwc.ac.za/index.php?module=etd&.
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The organisms in this study were chosen due to their associations with foods and their potential as food borne pathogens. Food borne diseases are an import public health problem in most countries. Bacteria of the genera Campylobacter, Salmonella and Listeria can be transported by poultry and poultry products to humans. Gastroenteritis, typhoid fever, diarrhea, dysentery may originate from the infection. This study was undertaken to determine the incidence of pathogens in a poultry processing plant using polymerase chain reaction and conventional tests and to determine the formation and survival of biofilm cells of food pathogens in trisodium phosphate.
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Bramwell, Penny. "The characterisation and detection of plant pathogenic streptomycetes in the natural environment." Thesis, University of Warwick, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357811.
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Marjenberg, Zoe R. "New prophylactic and therapeutic treatments to combat pathogenic enterohaemorrhagic Escherichia coli." Thesis, University of Glasgow, 2016. http://theses.gla.ac.uk/7689/.
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Bacterial diarrhoeal diseases have significant influence on global human health, and are a leading cause of preventable death in the developing world. Enterohaemorrhagic Escherichia coli (EHEC), pathogenic strains of E. coli that carry potent toxins, have been associated with a high number of large-scale outbreaks caused by contaminated food and water sources. This pathotype produces diarrhoea and haemorrhagic colitis in infected humans, and in some patients leads to the development of haemolytic uremic syndrome (HUS), which can result in mortality and chronic kidney disease. A major obstacle to the treatment of EHEC infections is the increased risk of HUS development that is associated with antibiotic treatment, and rehydration and renal support are often the only options available. New treatments designed to prevent or clear E. coli infections and reduce symptoms of illness would therefore have large public health and economic impacts. The three main aims of this thesis were: to explore mouse models for pre-clinical evaluation in vivo of small compounds that inhibit a major EHEC colonisation factor, to assess the production and role of two proteins considered promising candidates for a broad-spectrum vaccine against pathogenic E. coli, and to investigate a novel compound that has recently been identified as a potential inhibitor of EHEC toxin production. As EHEC cannot be safely tested in humans due to the risk of HUS development, appropriate small animal models are required for in vivo testing of new drugs. A number of different mouse models have been developed to replicate different features of EHEC pathogenesis, several of which we investigated with a focus on colonisation mediated by the Type III Secretion System (T3SS), a needle-like structure that translocates bacterial proteins into host cells, resulting in a tight, intimate attachment between pathogen and host, aiding colonisation of the gastrointestinal tract. As E. coli models were found not to depend significantly on the T3SS for colonisation, the Citrobacter rodentium model, a natural mouse pathogen closely related to E. coli, was deemed the most suitable mouse model currently available for in vivo testing of T3SS-targeting compounds. Two bacterial proteins, EaeH (an outer membrane adhesin) and YghJ (a putative secreted lipoprotein), highly conserved surface-associated proteins recently identified as III protective antigens against E. coli infection of mice, were explored in order to determine their suitability as candidates for a human vaccine against pathogenic E. coli. We focused on the expression and function of these proteins in the EHEC O157:H7 EDL933 strain and the adherent-invasive E. coli (AIEC) LF82 strain. Although expression of EaeH by other E. coli pathotypes has recently been shown to be upregulated upon contact with host intestinal cells, no evidence of this upregulation could be demonstrated in our strains. Additionally, while YghJ was produced by the AIEC strain, it was not secreted by bacteria under conditions that other YghJ-expressing E. coli pathotypes do, despite the AIEC strain carrying all the genes required to encode the secretion system it is associated with. While our findings indicate that a vaccine that raises antibodies against EaeH and YghJ may have limited effect on the EHEC and AIEC strains we used, recent studies into these proteins in different E. coli pathogens have suggested they are still excellent candidates for a broadly effective vaccine against E. coli. Finally, we characterised a small lead compound, identified by high-throughput screening as a possible inhibitor of Shiga toxin expression. Shiga toxin production causes both the symptoms of illness and development of HUS, and thus reduction of toxin production, release, or binding to host receptors could therefore be an effective way to treat infections and decrease the risk of HUS. Inhibition of Shiga toxin production by this compound was confirmed, and was shown to be caused by an inhibitory effect on activation of the bacterial SOS response rather than on the Shiga toxin genes themselves. The bacterial target of this compound was identified as RecA, a major regulator of the SOS response, and we hypothesise that the compound binds covalently to its target, preventing oligomerisation of RecA into an activated filament. Altogether, the results presented here provide an improved understanding of these different approaches to combating EHEC infection, which will aid the development of safe and effective vaccines and anti-virulence treatments against EHEC.
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Meaden, Sean McClarey. "The tri-trophic interaction of plants, pathogenic bacteria and bacteriophages." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/22133.
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The ecology and evolution of pathogens are key factors in predicting the severity and spread of disease, as well as treatment outcomes. However, the effects of multiple trophic levels that include host, microbial competitors and viruses are typically overlooked. In this thesis I develop our understanding of bacteria-phage coevolution, microbial dispersal and the role of the microbiome in disease. The results of these experiments have direct implications for phage therapy: the use of bacteriophages to treat bacterial infections. Firstly, I explore the risks of phage application in the environment and draw parallels with the misuse of antibiotics in selecting for bacterial resistance. I then demonstrate that the evolution of resistance to phages in a plant pathogenic bacterium is context-dependent. Notably, I find a fitness cost in plant infections that is absent when the bacteria are cultured solely in the laboratory. I then characterize four novel phages and use a simple laboratory based assay to predict their potential as phage therapy agents in an agricultural context. Next I show that reservoir species of plant hosts can affect the evolution of virulence, when bacteria are passaged on both a focal and distant host, but find no evidence of local adaptation. I also show that the evolution of such traits can occur in a parallel manner at the genetic level. I then determine a compositional shift in the microbiota associated with the symptoms of bleeding canker disease in Horse Chestnut trees across the length of the UK. Finally, I find an age-elated decline in bacterial species richness and evidence for niche-assembly theories by investigating bacterial dispersal in UK Oak trees in a single woodland.
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Brown, Kwame Agyapong. "Possible detection of pathogenic bacterial species inhabiting streams in Great Smoky Mountains National Park." Thesis, Western Carolina University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10244518.
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Numerous pathogenic bacterial species have been found in many freshwater systems around the world. These pathogens affect the overall water quality of these systems and may cause diseases in both aquatic and terrestrial animals which may lead to loss of species diversity and abundance in their environments. This study sought to identify and document pathogenic bacterial species that may inhabit the streams that flow through Great Smoky Mountains National Park. Bacterial cells were collected by filtering water from four streams (Oconaluftee River, Kephart Prong, Little Pigeon River and Hickory King Branch Stream) through separate capsule filters. The cells were later backflushed from the filters and cultured on various selective and differential media. Ten isolates were selected based on phenotypic characteristics such as colony color and growth on specific media type, and sample origin. The nearly full 16S rDNA was sequenced for all ten isolates and analyzed to determine their identity.
Out of the ten isolates, four isolates were from the phylum Firmicutes while the other six were in the phylum Proteobacteria. Phylogenetic analysis of these isolates showed eight out of the ten isolates were related to known opportunistic pathogens. The other two were related to a ubiquitous Bacillus species that is considered to be a probiotic. Although none of the isolates had a 100% match to a known obligate or opportunistic pathogen, many isolates matched > 97% to opportunistically pathogenic species. Follow up molecular and metabolic tests need to be employed to determine the pathogenicity of each isolate.
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Griffin, Blakeley. "A Study of the Polymicrobial Inhibitory Interactions Between Alcaligenes faecalis and Staphylococcus aureus." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/579.
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Members of the Staphylococcus genus are found as a part of normal microflora in humans and can commonly be found on the skin or in the nasal cavity. However, these microorganisms can cause serious and life-threatening opportunistic infections when there is a break in the physical barrier of skin. These infections have become difficult to treat as resistant strains emerge, particularly Methicillin Resistant Staphylococcus aureus (MRSA). MRSA has become a commonly acquired nosocomial infection which is difficult to treat with conventional antibiotics of the blactam class. Even Vancomycin, a last resort antibiotic, has been ineffective on some infections. Furthermore, S. aureus readily forms biofilms on implanted medical devices which establishes a hardy and difficult to treat infection. These biofilms serve as a point of infection to the bloodstream. Research involving polymicrobial interactions and the inhibitory effects of bacterial-bacterial interactions could be a starting point for the discovery of a new therapeutic treatment for infections. It has been shown in our lab that Alcaligenes faecalishas inhibitory effects on Staphylococcus aureusplanktonic growth. Therefore, in this study, we wanted to examine 1) The mechanism by which A. faecalisinhibitsS. aureus growth and 2) how A. faecalisimpacts the various phases of S. aureusbiofilm growth. It was found that A. faecalislikely inhibits S. aureususing a physical mechanism that requires close contact, rather than using a secreted molecule. However, a Type VI secretion system could also produce similar results. Further research involving the formation of mutants to find the gene allowing A. faecalisto inhibit S. aureuswas started, but no viable mutants were created during the course of this research. A. faecaliswas found to inhibit the formation of S. aureus biofilm growth, but when added to a mature S. aureusbiofilm, the slow growth rate of A. faecaliscould not overtake the quickly replicating S. aureus. Further research in the polymicrobial interactions between S. aureus and A. faecaliscould lead to a finding of a new therapeutic target for antibiotics or the use of A. faecalisin infections.
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Crossley, Brian E. "Role of the Exopolysaccharide Alginate in Adherence to and Inflammation of Pulmonary Epithelial Cells." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4473.
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Pseudomonas aeruginosa (PA) infections in Cystic Fibrosis (CF) patients are not easily cleared due to the conversion from a nonmucoid to a mucoid phenotype. Alginate is an acetylated exopolysaccharide produced by mucoid PA that is responsible for increased resistance to antibiotics, host phagocytic killing, and propagating biofilm formation. Understanding the interaction between PA and host cells is critical to understanding chronic infection and inflammation in CF. In order to investigate this, we used A549 pulmonary epithelial cells and murine alveolar macrophages (MH-S) to examine host response to nonmucoid versus mucoid PA infection. Adhesion assays in A549 pulmonary epithelial cells revealed that mucoid PA mutants adhere poorly compared to their nonmucoid counterparts. Similarly, phagocytosis assays using MH-S infected with PA revealed that mucoid PA are increasingly resistant to phagocytosis. The alginate acetylation mutant FRD1175 is more susceptible to phagocytic killing than alginate+ FRD1. Adherence and phagocytosis of mucoid FRD1 was increased by increasing the multiplicity of infection (MOI) from 50:1 to 500:1. Furthermore, confocal microscopy revealed that mucoid PA are inherently less inflammatory than nonmucoid strains in both A549 and MH-S. Increasing the MOI of mucoid FRD1 from 50:1 to 500:1 significantly increased caspase-1 activation in MH-S but not in A549, revealing that intensity of inflammatory signaling by epithelial cells is likely independent of increased adherence. FRD1175 infection in both A549 and MH-S revealed that alginate acetylation plays a significant role in reducing inflammasome activation. Western analysis revealed that PA does not actively induce TGF-β secretion by A549 epithelial cells. Similarly, NF-κB expression was reduced in both A549 and MH-S when infected with mucoid FRD strains, but not PA from the PAO background, suggesting FRD strains have accumulated additional mutations facilitating escape of inflammation. MH-S treated with cytochalasin D to block phagocytosis were still able to activate NF-κB signaling, suggesting NF-κB activation is adherence but not phagocytosis dependent. These data increase our understanding of the various mechanisms in which mucoid PA is able to evade host immune defenses and provides insight into potential therapies to treat PA infections.
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Mansour, Michael K. "Host response to mannosylated proteins from the pathogenic yeast, Cryptococcus neoformans." Thesis, Boston University, 2005. https://hdl.handle.net/2144/37166.
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Thesis (Ph.D.)--Boston UniversityPLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
The pathogenic yeast, Cryptococcus neoformans , is a leading cause of death among individuals with compromised T cell function. Mannoproteins (MP) are a set of functionally heterogeneous, heavily mannosylated glycoforms found in many fungal species including C. neoformans. Cryptococcal MP have been shown to stimulate cell-mediated immunity and pro-inflammatory cytokines, both vital for the clearance of this yeast. As it is unclear how MP elicit immunity, it was hypothesized that the extensive conjugated carbohydrate backbone present on MP plays an essential role in immune stimulation. Mannose receptors (MR), including the macrophage mannose receptor (MMR) and dendritic cell-specific ICAM-3-grabing nonintegrin (DC-SIGN), both present on antigen-presenting cells (APC) and known to recognize mannosylated pathogens were shown to bind MP. Deglycosylation of MP or MR blockade with competitive mannosylated ligands inhibited T-cell activation. The immunodominant APC responsible for immune stimulation was determined by incubating T cells with purified splenic dendritic cells (DC), B cells, and peritoneal macrophages. T cells responded to MP only in the presence of DC. In addition, whole splenocyte populations, but not DC-depleted splenocytes, stimulated MP-specific T cells. Comparing APC populations, only DC captured fluorescent MP in a MR-dependent process. The kinetics of MP capture appear to involve 2 processes, a major, rapid, saturable receptor-mediated process that is inhibited with mannan, and minor pinocytic uptake. Impressively, DC pulsed for short periods with MP were still able to functionally stimulate T cells in a MR-dependent mechanism. Confocal microscopy of MP in DC at early time points indicated co-localization with transferrin, MMR and DC-SIGN suggesting MP enters early endosomes via MR. Subsequently, MP enter degradative perinuclear compartments. In vivo, MP-immunization resulted in increased survival, as well as a decrease in organ fungal load in response to live C. neoformans challenge. This partial protection was dependent on T cells, and not B cells. Moreover, analysis of tissue pro-inflammatory cytokine levels showed an increase in tumor necrosis factor-α and interferon-γ in infected MP-immunized mice. Collectively, these studies begin to provide both a molecular and cellular basis for the immunogenicity of cryptococcal MP and support T cell vaccination strategies that target MR and DCs.
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Lövkvist, Lena. "Receptor Interactions Between Pathogenic Bacteria and Host Cells." Doctoral thesis, Uppsala University, Department of Medical Biochemistry and Microbiology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7782.
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This thesis focuses on host and pathogen specific interactions during invasive disease. We have investigated the role and impact of different virulence factors of Neisseria gonorrhoeae, N. meningitidis and Streptococcus pyogenes on host epithelial cells and in vivo.
N. gonorrhoeae cause the sexually transmitted disease gonorrhoea and N. meningitidis is the most common cause of bacterial meningitis and may be leathal to the host within hours of infection. The neisserial type IV pili were shown to have an important impact on host cells for the induction of pro-inflammatory and other cellular defence transcriptional responses. Furthermore, N. meningitidis generally induced an earlier response compared to N. gonorrhoeae, probably as a result of the meningococcal capsule. The role of N. meningitidis serogroup B lipooliogsaccharide was investigated during invasive disease. Bacterial invasion of host cells and blood survival as well as virulence in vivo was dependent on the integrity of the LOS structure.
S. pyogenes may cause a variety of diseases ranging from uncomplicated diseases such as 'strep-throat' to more severe invasive diseases such as necrotizing fasciitis and streptococcal toxic shock syndrome. S. pyogenes ScpC protease degrade interleukin 8 during necrotizing fasciitis. We investigated the role of ScpC in systemic disease and observed enhanced virulence by bacteria unable to degrade IL-8. Following an intravenous infection of mice pro-inflammatory cytokines and complement activation was induced by the ScpC negative mutant compared to the wild-type and correlated with higher bacteremia. These data indicate that the precense of the ScpC protease has an important impact on the host for the outcome of streptococcal sepsis. Another phagocytic escape mechanism of S. pyogenes is their ability to coat themselves with host proteins. We observed that released complement control protein, CD46, bound to the streptococcal cell surface. CD46 has been shown to interact with the streptococcal M protein and have now been found to bind to the surface of the bacteria in a growth phase dependent manner. We observed a more aggressive disease development in CD46 transgenic mice after an intravenous infection with an M6 serotype, resulting in higher mortality of CD46 transgenic mice compared with control mice. These data indicate that CD46 may confer a protection to the streptococci during early stage of systemic infection and contributes to the understanding of immune evsion of S. pyogenes.
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Nyenje, Mirriam E. "Genetic and phenotypic characterisation of foodborne bacteria isolated from ready-to-eat foods in Alice, South Africa." Thesis, University of Fort Hare, 2014. http://hdl.handle.net/10353/d1016109.
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Foodborne illnesses following the ingestion of contaminated food are a major public health problem worldwide. They include a broad group of illnesses ranging from mild to chronic or life-threatening; caused by either toxins released from the disease-causing microbes, or by the microbes themselves. Antimicrobial susceptibility data shows an alarming increase in the frequency of antimicrobial resistance of foodborne pathogens, a situation which is worrisome as it decreases the effectiveness of drugs employed to reduce the morbidity and mortality associated with serious and life-threatening infections and thus, compromising human health. This study was therefore designed to assess the occurrence and characterization of bacterial foodborne pathogens in various foods sold in Alice, Eastern Cape Province of South Africa in an effort to throw more light on the inherent risk associated with such foods. The study was conducted during the period of 2011 - 2013. Two university restaurants and eight ready-to-eat food vending sites in Alice Town were selected based on their prominence to the students, workers and rest of the community. Microbiological analysis was conducted on 252 samples which included vegetables, potatoes, rice, pies, beef and chicken stew. The isolates were identified using biochemical tests and confirmation of the two most prevalent organisms (Listeria ivanovii and Enterobacter cloacae) was done using PCR techniques. The antimicrobial susceptibility profile of Listeria ivanovii and Enterobacter cloacae strains were identified using the disc diffusion technique; minimum inhibitory concentration was determined by the broth dilution method and M.I.C. Evaluator test strips. The microtiter plate adherence assay was employed to ascertain the ability of these isolates to adhere to a surface whereas the role of cell surface properties in biofilm formation was assessed using the coaggregation and autoaggregation assays. The architecture of the formed biofilms was examined under the scanning electron microscope. The virulence and resistant genes were also detected and characterised by sequencing the PCR products. Bacterial growth was present in all the food types tested; organisms isolated included: Listeria spp. (22%), Enterobacter spp. (18%), Aeromonas hydrophila (12%), Klebsiella oxytoca (8%), Proteus mirabilis (6.3%), Staphylococcus aureus (3.2%) and Pseudomonas luteola (2.4%). PCR confirmed 30 (97%) isolates as E. cloacae complex while 44% (22/50) tested positive for L. ivanovii. All the strains of E. cloacae (100%) and 96% of L. ivanovii isolates (based on phenotypic identification) were resistant to at least four or more of the antibiotics. In this study, bla-TEM was also detected from 48 (96%) of L. ivanovii and 30 (100%) of E. cloacae strains; further analysis of the bla-TEM demonstrated the occurrence of bla-TEM-1. Of the 56 bla-TEM-1 positive isolates sequenced, 7% (4/56) had mutation of either insertion or substitution of a nucleotide. Two virulence genes (ucaA and hlyA) were detected in E. cloacae isolates and none in L. ivanovii using PCR. Sequence analysis of the hsp60 gene reported the presence of two sub-species for E. cloacae; E. cloacae cluster III (75%) and E. cloacae cluster IV (25%); while analysis of the iap60 gene demonstrated that 55.8% (19/34) were L. ivanovii, 44% (15/34) L. seeligeri and 14.7% (5/34) L. welshemeri. A total of 90% L. ivanovii and 88% E. cloacae strains demonstrated the ability to form biofilms; the coaggregation index ranged from 12 to 77% while the autoaggregation index varied from 11 to 55% for L. ivanovii and 27% to 98% for E. cloacae. The findings of this study indicate that most of the ready-to-eat food samples examined did not meet bacteriological quality standards, thus posing potential risks to consumers. This should draw the attention of the relevant authorities to certify that hygienic standards are improved to curtain foodborne infections. Furthermore, the presence of multi-resistant strains is of major concern as these foods could serve as important vehicles transmitting multi-resistant bacteria and genes to humans. In addition the ability of these pathogens to form biofilms may lead to adherence of these organisms to kitchen utensils and other environments leading to cross-contamination of food processed in these areas and increase resistance of organisms to antimicrobial agents.
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Younson, Justine Sarah. "The paradoxic effects of sub-inhibitory concentrations of ciprofloxacin on pathogenic determinants in coagulase-negative staphylococci." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286761.
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Yeung, Ralph. "The role of zinc cluster protein transcription factors in regulating antifungal resistance in pathogenic yeast «Candida glabrata»." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=87011.
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Candida glabrata is an emerging opportunistic fungal pathogen which is the overall second leading contributor after Candida albicans in all candidiasis infections, especially in patients with compromised immune systems, such as patients who suffer from AIDS or have received organ transplants. This study focuses on the transcription factor activity of zinc cluster proteins, which are found only in fungi, and their relationship to antifungal resistance. In contrast to Saccharomyces cerevisiae and to some extent C. albicans, the role and mechanisms of zinc cluster proteins in drug resistance in C. glabrata has not been as thoroughly investigated in depth in the literature. The goal of this study was to generate a panel of deletion strains for putative zinc cluster genes by using a gene deletion strategy, for example in the deletion of MRR1. By using phenotypic assays on the generated knockout strains, insight regarding possible mechanistic relationships between zinc cluster proteins to drug resistance could be obtained.Candida glabrata est un mycète pathogène opportuniste et est la deuxième cause (après Candida albicans) des infections de type candidiasis, particulièrement chez les patients ayant des déficiences du système immunitaire, dont ceux souffrant du SIDA, du cancer ou ayant reçu des greffes d'organes. Cette étude se porte sur l'activité des facteurs de transcription de la famille des protéines à groupe de zinc (trouvées seulement chez les mycètes) et leur relation à la résistance antimycotique. Par contraste avec Saccharomyces cerevisiae, le rôle et les mécanismes des protéines à groupe de zinc dans la résistance aux médicaments chez C. glabrata n'ont pas été examinés en détail. Le but de cette étude était de générer des souches comportant une délétion dans chaque gène de la famille des protéines à groupe de zinc. En utilisant des essais phénotypiques sur les souches de délétions obtenues, il sera possible d'en apprendre plus sur les relations entre les protéines à groupe de zinc et la résistance aux médicaments chez C. glabrata.
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Hayward-McClelland, Shannon Faith. "Investigation into the potential involvement of apoptosis in the pathogenic mechanisms of the protozoan parasite Trichomonas vaginalis." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9449.
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Our hypothesis proposed that Trichomonas vaginalis would induce apoptosis in host cells as part of its pathogenic assault. This hypothesis was tested in an established co-culture system; previous research demonstrated that the parasite destroyed McCoy cell monolayers. The TUNEL assay was used to identify cells undergoing apoptotic DNA fragmentation as a result of co-incubation with T. vaginalis. Early experiments suggested that apoptosis may have been occurring in the McCoy monolayers, but this was later disproved with the help of a sandwich ELISA to detect DNA/histone fragments that characteristically result from apoptosis. Instead, the cells that had originally been identified as apoptotic were found to be adherent trichomonads. While McCoy cell apoptosis in response to co-culture with T. vaginalis was not observed, T. vaginalis did, over time, cause detachment of almost all monolayer cells, and also caused irreparable damage in a portion of these cells. Induction of McCoy monolayer detachment was determined to be contact-independent, given that trichomonad culture supernatants had a similar effect. (Abstract shortened by UMI.)
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Nespolo, Natália Maramarque [UNESP]. "Características microbiológicas de salmão (Salmo salar) comercializado em algumas cidades da região nordeste do estado de São Paulo." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/94656.
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Tem sido evidente o aumento no consumo de pescado, especialmente do salmão (Salmo salar) sob a forma “in natura”, em pratos da cozinha oriental. Como conseqüência, tem havido maior preocupação quanto às suas características higiênico-sanitárias, tendo em vista a facilidade que microrganismos encontram para se desenvolverem em sua carne, o que pode expor os consumidores a agentes que causam desde uma simples gastrenterite até o óbito. Diante desta preocupação, desenvolveu-se este estudo com objetivos de avaliar características microbiológicas do salmão por meio da quantificação de microrganismos heterotróficos mesófilos, coliformes totais e termotolerantes, o perigo de veiculação de Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella sp., Escherichia coli e Aeromonas sp. através da carne e contribuir com subsídios técnicos para criar uma legislação brasileira com padrões microbiológicos específicos para o pescado consumido cru. Foram colhidas 31 amostras de salmão, 16 refrigeradas e 15 congeladas, no comércio varejista de cidades da região nordeste do estado de São Paulo. Os resultados obtidos mostram populações de microrganismos heterotróficos mesófilos variando entre 1,0 x 10 e 3,9 x 106 UFC/g, coliformes totais e termotolerantes em, respectivamente, 32,24% e 19,33% das amostras e Aeromonas sp. em 35,48% das amostras com variação populacional de 2,0 x 102 a 8,0 x 103 UFC/g. Ainda houve a presença de Staphylococcus aureus em uma amostra e ausência de Vibrio parahaemolyticus, Salmonella sp. e Escherichia coli. Os resultados obtidos podem servir de parâmetro para a criação de um padrão microbiológico específico para o pescado consumido cru e servem também de alerta para os consumidores do produto tendo em vista a veiculação de microrganismos potencialmente patogênicos.
The increasing of seafood consumption has become evident especially in the use of salmon (Salmo salar) consumed raw in oriental dishes. Consequently, it has risen up the concern related to their hygienic-sanitary characteristics due to the facility that microorganisms multiply in the meat which can expose consumers to the causative agents of a mild gastroenteritis until the death. Regarding such informations, this study was aimed to evaluate microbiological characteristics of salmon by quantifying microrganisms heterotrophic mesophiles, total coliforms and thermotolerant. It was also evaluated the danger of transmission of Vibrio parahaemolyticus, Staphylococcus aureus, Salmonella sp., Escherichia coli and Aeromonas sp. on the fish muscle and contributed to technical informations to create a Brazilian regulations about specific microbiological standards for consumption of raw seafood. Thirty-one samples of salmon were collected, 16 chilled and 15 frozen, from the retail market in cities of the northeast region of São Paulo State. The results show populations of mesophilic heterotrophic microorganisms ranging from 1.0 x 10 and 3.9 x 106 CFU/g, in total and fecal coliforms, respectively, 32.24% and 19.33% of samples and Aeromonas sp. in 35.48% of samples ranging population of 2.0 x 102 to 8.0 x 103 CFU/g. Staphylococcus aureus was present in one sample and were not found Vibrio parahaemolyticus, Salmonella sp. and Escherichia coli. The results may serve as a parameter for the establishment of a microbiological standard for the consumption of raw seafood and also as a warning to consumers of the product for the presence of potentially pathogenic microorganisms.
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Ansari, Shamim Alam. "Studies on the potential of hands as vehicles for the spread of selected human pathogenic viruses and bacteria." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/5906.
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In this study, a simple protocol was developed to test the survival of a human rotavirus (HRV), rhinovirus type 14 (RV-14), and parainfluenzavirus type 3 (HPIV-3) as well as Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) on human hands. HPIV-3 lost nearly all of its infectivity within the first 60 minutes on the fingerpads. In contrast to this, nearly 16% of infectious RV-14 could be recovered even after 3 hours. The poor survival of HPIV-3 on human hands prompted us to investigate its survival on stainless steel disks (1 cm in diam.) under ambient conditions. The ability of the two respiratory viruses to survive well on non-porous inanimate surfaces indicates that, once contaminated, these surfaces may act as a potential virus source. To study the patterns of virus transfer, the following three experimental models were developed and tested: finger-to-finger, finger-to-disk and disk-to-finger. The results suggest that human hands and environmental surfaces, singly or in combination, have the potential to spread rotaviral infections, particularly in institutional settings. The comparatively rapid loss of HPIV-3 infectivity on hands may reduce their potential as vehicles for transmission. These results also suggest a role for environmental surfaces in the contamination of hands with respiratory viruses. We compared the efficiency of paper-, cloth- and an electric blow dryer in further reducing the level of infectious rotavirus and E. coli remaining on fingerpads washed with either 70% isopropanol, Savlon in water (1:200), an unmedicated liquid soap, or tap water alone. Irrespective of the hand-washing agent used, warm air drying produced the greatest and the cloth the smallest reduction in the numbers of both test organisms. These findings indicate the importance of the proper drying of washed hands, particularly when less effective hand-washing agents are used. The results of this study show that HRV, RV-14 and S. aureus can survive on human hands long enough to permit their spread through hands. In contrast to this, parainfluenzaviruses and E. coli appeared to be limited in their capacity to survive on hands. The differences found in the efficacy of commonly used hand-washing agents against HRV and the bacteria tested point to the importance of testing such products by proper in vivo protocols using representative viruses. (Abstract shortened by UMI.)
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Manshadi, Faezeh Dehghan. "Occurence of pathogenic and indicator microorganisms on produce irrigated with dairy wastewater." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289980.
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This project was designed to assess the potential for contamination of produce during irrigation with wastewater from animal operations. Dairy wastewater from the University of Arizona Campus Dairy Research Center was used to irrigate three different types of vegetable crops: lettuce, carrot, and bell pepper. This study was conducted over two consecutive years. The crops were planted in February and vegetables were harvested from May through July. Irrigation water and vegetable samples were examined for Escherichia coli, Clostridium perfringens, Listeria monocytogenes, and coliphage. In the dairy wastewater, E. coli concentrations averaged 5.7 x 10⁵ MPN/100 mL in the first year (2000), and 9.9 x 10⁷ MPN/100 mL in the second year (2001). C. perfringens concentrations were nearly the same in both years (1.7 x 10⁴ and 3.4 x 10⁴ CFU per 100 mL). Coliphage averaged 2.0 PFU/mL in 2000 and 1.3 x 10⁴ PFU/mL in 2001 in wastewater. E. coli was detected with greater frequency on carrots (100 and 96%) succeeded by lettuce (67 and 96%) and bell peppers (63 and 58%). The same was true for C. perfringens : carrots (100%), lettuce (86 and 88%), and bell peppers (100 and 50%). Coliphages were not detected on any of the vegetable crops except for average concentrations of 2 PFU/g on lettuce in the first year. L. monocytogenes was not detected on any of the vegetable samples. ANOVA test results indicates that E. coli and C. perfringens concentrations on three crops were statistically different (p < 0.0001) which suggest that the degree of contamination on the surface of the vegetables depends on where the edible portion of the crop is situated (above the soil or under the soil). The greatest contamination occurred on the carrots followed by lettuce and bell peppers. E. coli and C. perfringens were recovered from the carrots, bell peppers, and soil 55 days after wastewater irrigation of the plots had ceased. Positive correlations (p < 0.05) were found between E. coli and C. perfringens density and soil moisture content. The greatest risk of infection from pathogenic E. coli (O157:H7) occurs from consumption of lettuce and carrots. The annual risk of infection from consumption of all three vegetables was above the acceptable risk of 1:10,000 per year. The results of this study suggest that a more strict irrigation water quality standard for root and leafy vegetables might be appropriate to prevent the risk of infection in exposed population.
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Botes, Marelize. "Survival of probiotic lactic acid bacteria in the intestinal tract, their adhesion to epithelial cells and their ability to compete with pathogenic microorganisms." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/21554.
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Thesis (PhD)--Stellenbosch University, 2008.ENGLISH ABSTRACT: Research on probiotics has increased over the past years, which led to commercialization of a number of probiotic supplements and functional foods. In vitro assays such as tolerance to acid and bile, adhesion to mucus and epithelial cells, antimicrobial activity and antibiotic resistance tests are performed to screen lactic acid bacteria for probiotic properties. Enterococcus mundtii ST4SA produces an antimicrobial peptide (peptide ST4SA) with activity against Gram-positive and Gram-negative bacteria. Lactobacillus plantarum 423 produces plantaricin 423, a typical class II bacteriocin, active against a number of Gram-positive bacteria. A gastro-intestinal model (GIM) simulating the gastro-intestinal tract (GIT) of infants, was developed to study the survival of E. mundtii ST4SA and L. plantarum 423 and evaluate them as possible probiotics. Growth of the two strains in the GIM was compared to the growth of commercially available probiotics. Infant milk formulations were used as growth medium. Changes in pH, the addition of bile salt and pancreatic juice, and intestinal flow rates were controlled by peristaltic pumps linked to a computer with specifically designed software. Strain ST4SA was sensitive to low pH and high concentrations of bile salts. Growth of strain ST4SA was repressed in the first part of the GIM, however, the cells recovered in the ileum. Strain 423 was also sensitive to acidic conditions. However, the cells withstood the presence of bile and pancreatin in the first part of the GIT. Neither of the two strains displayed bile salt hydrolase (BSH) activity. Both strains were resistant to amoxicillin, ampicillin, chloramphenicol, cefadroxil, roxithromycin, meloxicam, doxycycline, erythromycin, novobiocin, rifampicin, tetracyclin, bacitracin, oflaxacin and cephazolin, anti-inflammatory drugs Na+- diklofenak and ibuprofen, and painkillers codeine terprim hydrate aminobenzoic acid, metamizole aspirin and paracetamol. Strain 423 was resistant to ciprofloxacin. Genes encoding cytolysin, non-cytolysin β-hemolysin and cell aggregation substances were detected on the genome of strain ST4SA but they were not expressed. L. plantarum 423 does not contain genes encoding gelatinase, cell aggregation, enterococcus surface protein, hemolysin, non-cytolysin β- hemolysin and enterococcus endocarditis antigen. Both strains inhibited the growth of Listeria monocytogenes ScottA in the GIM. Survival of the strains improved when used in combination and compared well with the survival of commercially available probiotics. Adhesion to epithelial cells is an important prerequisite for bacterial colonization in the GIT. The adhesion of E. mundtii ST4SA and L. plantarum 423 was studied using Caco-2 (human colon carcinoma epithelial) cells. Both strains revealed good adhesion compared to other probiotic strains. No correlation was found between hydrophobicity, auto-aggregation and adhesion to Caco-2 cells. Antibiotics and anti-inflammatory medicaments had a negative effect on adhesion. Different combinations of proteins were involved in the adhesion of E. mundtii ST4SA and L. plantarum 423 to Caco-2 cells. E. mundtii ST4SA, L. plantarum 423 and L. monocytogenes ScottA were stained with fluorescent dyes to visualize adhesion to Caco-2 cells. Adhesion of L. monocytogenes ScottA to Caco-2 cells was not reduced in the presence of strains ST4SA and 423. Cell-free culture supernatants of both strains inhibited the invasion of L. monocytogenes ScottA. The cell structure of Caco-2 cells changed in the presence of L. monocytogenes ScottA. Strains ST4SA and 423 protected Caco-2 cells from deforming.
AFRIKAANSE OPSOMMING: Navorsing op probiotika het die afgelope tyd drasties toegeneem en aanleiding gegee tot die kommersialisering van ‘n groot hoeveelheid probiotiese supplemente en funksionele voedselsoorte. In vitro studies, soos bv. weerstand teen suur en gal, vashegting aan mukus en epiteelselle, antimikrobiese aktiwiteit en weerstand teen antibiotika word uitgevoer om te bepaal of melksuurbakteriëe aan probiotiese standaarde voldoen. Enterococcus mundtii ST4SA produseer ’n peptied met antimikrobiese werking teen Grampositiewe en Gram-negatiewe bakteriëe. Lactobacillus plantarum 423 produseer ‘n tipiese klas II bakteriosien, plantarisien 423, met aktiwiteit teen sekere Gram-positiewe bakteriëe. ’n Gastro-intestinale model (GIM) wat die spysverteringskanaal (SVK) van babas simuleer, is ontwikkel om die oorlewing van E. mundtii ST4SA en L. plantarum 423 te bepaal en hul eienskappe met dié van kommersiële probiotiese stamme te vergelyk. Babamelk formules is as groeimedium gebruik. Verandering in pH, byvoeging van galsoute en pankreassappe, en intestinale vloei is met behulp van peristaltiese pompe gereguleer wat seine vanaf ‘n spesiaal ontwikkelde rekenaarprogram ontvang. E. mundtii ST4SA was sensitief vir lae pH en hoë galsoutkonsentrasies en groei is in die eerste deel van die GIM onderdruk. Selgetalle het wel in die ileum herstel. Stam 423 was ook sensitief vir lae pH, maar het die galsout- en pankreatienvlakke in die laer deel van die SVK weerstaan. Geen galsout-hidrolase aktiwiteit is by enige van die twee stamme gevind nie. Beide stamme het weerstand getoon teen amoksillien, ampisillien, chloramfenikol, cefadroksiel, roksitromisien, meloksikam, doksisiklien, eritromisien, novobiosien, rifampisien, tetrasiklien, basitrasien, oflaksasien, kefazolien, die anti-inflammatoriese medikamente Na+-diklofenak en ibuprofen, en die pynstillers kodeïenterprimhidraataminobensoësuur, metamisoolaspirien en parasetamol. L. plantarum 423 was bestand teen ciprofloksasien. Gene wat kodeer vir sitolisien, nie-sitolisien β-hemolisien III en sel-aggregasie is op die genoom van E. mundtii ST4SA gevind, maar word nie uitgedruk nie. L. plantarum 423 besit nie die gene wat vir gelatinase, selaggregasie substansies, enterokokkus selwandproteïen, hemolise, nie-sitolisien β-hemolisien en enterokokkus endokarditis antigeen kodeer nie. Albei stamme inhibeer die groei van Listeria monocytogenes ScottA in die GIM. Die twee stamme in kombinasie het tot beter oorlewing in die GIM gelei. Stamme ST4SA en 423 vergelyk goed met kommersieël beskikbare probiotika. Vashegting van probiotiese stamme aan epiteelselle is belangrik vir kolonisering in die SVK. Vashegting van E. mundtii ST4SA en L. plantarum 423 is bestudeer deur van Caco-2 (kolon epiteel) selle van die mens gebruik te maak. Die aanhegting van beide stamme aan Caco-2 selle het goed vergelyk met kommersieël beskikbare probiotiese stamme. Geen korrelasie is gevind tussen hidrofobisiteit, aggregasie en vashegting aan Caco-2 selle nie. Antibiotika en antiinflammatoriese medikamente het ‘n negatiewe effek op vashegting gehad. Verskillende kombinasies van proteïene is betrokke in die vashegting van E. mundtii ST4SA en L. plantarum 423 aan Caco-2 selle. E. mundtii ST4SA, L. plantarum 423 en L. monocytogenes ScottA is met fluoreserende kleurstowwe gemerk om vashegting aan Caco-2 selle te monitor. Vashegting van L. monocytogenes ScottA aan Caco-2 selle is nie deur die teenwoordigheid van stamme ST4SA en 423 beïnvloed nie. Sel-vrye kultuursupernatante van beide stamme het die binnedring van L. monocytogenes ScottA verhoed. Die selstruktuur van Caco-2 selle het in die teenwoordigheid van L. monocytogenes ScottA van vorm verander. E. mundtii ST4SA en L. plantarum 423 het die Caco-2 selle teen vervorming beskerm.
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Abd, Hadi. "Interaction between waterborne pathogenic bacteria and Acanthamoeba castellanii /." Stockholm, 2006. http://diss.kib.ki.se/2006/91-7140-569-0/.
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Spitali, Mariangela. "The sidechain structure of lipopolysaccharide from plant pathogenic pseudomonads in relation to their antigenicity." Thesis, University of Greenwich, 1993. http://gala.gre.ac.uk/6306/.
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Ferguson, Christobel Margaret Biotechnology & Biomolecular Science UNSW. "Deterministic model of microbial sources, fate and transport: a quantitative tool for pathogen catchment budgeting." Awarded by:University of New South Wales. Biotechnology and Biomolecular Science, 2005. http://handle.unsw.edu.au/1959.4/23451.
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The most important priority for the management of Australian drinking water catchments is the control of pathogen loads delivered to raw water reservoirs and treatment plant intakes. A process-based mathematical model was developed to estimate pathogen catchment budgets (PCB) for Cryptosporidium, Giardia and E. coli loads generated within and exported from catchments. The model quantified key processes affecting the generation and transport of microorganisms from humans and animal excreta using land use and hydrologic data, and catchment specific information including point sources such as sewage treatment plants and on-site systems. The PCB model was applied in the Wingecarribee catchment, Sydney and used to predict and rank pathogen and indicator loads in dry weather, intermediate (<30 mm in 24 h) and large wet weather events (100mm in 24 h). Sensitivity analysis identified that pathogen excretion rates from animals and humans, and manure mobilisation rates were the most significant factors determining the output of the model. Comparison with water quality data indicated that predicted dry weather loads were generally within 1-2 log10 of the measured loads for Cryptosporidium and E. coli and within 1 log10 for Giardia. The model was subsequently used to predict and rank pathogen and indicator loads for the entire (16 000 km2) Sydney drinking water catchment.
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Quinonez-Diaz, Maria de Jesus. "Removal of pathogenic and indicator microorganisms from wastewater by natural systems." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282861.
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The purpose of this study was to determine the removal efficiency of natural systems for the reduction of enteric protozoa (Giardia and Cryptosporidium), and enteric viruses in wastewater. The first part of the study used bench-scale soil columns to determine the potential effectiveness of Soil Aquifer Treatment (SAT) for the removal of Cryptosporidium oocysts and Giardia cyst from treated wastewater. Sand and sandy loam were used to pack 18 to 200-cm long columns. Results from this study showed that removal of oocysts increased as increasing length of the soil column. Although substantial removal of Cryptosporidium occurs (>99.99%) within 200 cm of soil, oocysts are likely to penetrate beyond this depth. Giardia was removed far below detectable levels, probably due to its larger size. The next phase of the project investigated the removal of pathogenic and indicator microorganisms from untreated wastewater by a surface flow wetland, the importance of plants in wetlands, as well as the potential for groundwater contamination passed by pathogens with the use of constructed wetlands. This small-scale study was conducted in a large tank divided into two cells. Both cells were filled with sand and one cell was planted with bulrushes and the other was unplanted. About 90 percent of all microorganisms were removed by either of the systems. Neither Giardia nor Cryptosporidium were found to penetrate through the 2-m of sand in either the planted or unplanted cells. Lower numbers of viruses and bacteria were transported through the sand in the planted wetland cell versus the unplanted cell. This could indicate that vegetated wetlands are more likely to prevent microbial transport to groundwater. The objective of the last part of this study was to determine the survival of Cryptosporidium oocysts in wastewater effluent applied to a constructed vegetated wetland, when exposed to and when protected from sunlight, and the effect of temperature during different seasons. Viability of Cryptosporidium oocysts was determined using the excystation technique. Results from this study indicated that sunlight and/or temperature play a significant role in the survival of Cryptosporidium. Thus, it was concluded that oocyst reduction in wastewater applied to wetlands can be enhanced by natural die-off due to the effects of temperature or UV irradiation in sunlight, and greater removal could be achieved if designing of wetland systems take into consideration such factors.
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Gilfilan, Dennis, Phillip R. Scheuerman, and T. Andrew Joyner. "Seasonal and Spatial Variations in the Probability of Pathogenic Stream Impairment." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2956.
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Fuqua, Andrew. "Characterization of the Broad-spectrum Inhibitory Capability of Alcaligenes faecalis and A. viscolactis against Potential Pathogenic Microorganisms." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/546.
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The recent rise of multidrug resistant microorganisms has grown from an isolated concern to a massive public health crisis. It has become imperative that scientists look for new ways to combat this issue. Due to the selective pressures of competition, bacteria and other microbes possess a host of defenses and weapons designed to exploit vulnerabilities in other microorganisms. Consequently, the study of these systems and microbial interactions has much to reveal in the search for novel antimicrobial treatments. Previous research from our laboratory has discovered that both Alcaligenes faecalis and Alcaligenes viscolactis, two rarely studied and generally non-virulent bacteria, exert a microbicidal effect on Candida albicans and Staphylococcus aureus, two pathogenic and frequently drug-resistant organisms. In this study, we confirmed that these effects are via a live-cell, contact-dependent mechanism and showed that both Alcaligenes species inhibit S. aureus at the attachment phase of biofilm growth. Additionally, we found that A. faecalis and A. viscolactis target Gram-positive bacteria outside the genus Staphylococcus and certain Gram-negative species as well as Candida glabrata. This study also provides novel evidence of a putative Type VI Secretion System in both Alcaligenes species, which may explain their antimicrobial phenotype. Despite efforts to identify the genetic elements involved via mutagenesis, the mechanism of these interactions remain elusive due to the difficulty of gene transfer in these organisms. We hope these results will increase current knowledge of Alcaligenes’ capabilities and genetic composition as well as establish the groundwork for future efforts to discover its inhibitory system and mechanisms.
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Lamb, Kelsey Ellen. "THE SURVIVAL OF VARIOUS PATHOGENIC ORGANISMS IN FATS AND OILS." UKnowledge, 2017. http://uknowledge.uky.edu/animalsci_etds/72.
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The research within this thesis sought to determine the ability of various animal derived fats and plant derived oils to support the survival of several pathogenic cocktails over a multitude of storage times. The Salmonella study explored the survival rate of a four strain Salmonella cocktail in beef tallow, pig lard, duck fat, coconut oil, and extra virgin olive oil over seven days at 26˚C and 37˚C storage. The animal fats and the coconut oil supported the survival of the bacteria until the conclusion of the study. The Shiga-toxin producing Escherichia coli study explored the survival rate of a five strain STECs cocktail in extra virgin olive oil over seven days at 26˚C and 37˚C storage. The two Listeria studies explored the survival rate of a four strain Listeria monocytogenes cocktail in extra virgin olive oil over several time periods with different frequencies of sample mixing. In vitro, all genuses showed a 2.5-log cfu/mL to ≥ 7-log cfu/mL reduction in the extra virgin olive oil by the conclusion of the experiments. Extra virgin olive oil was then applied to cooked pork tenderloin, cheddar cheese snack squares, and turkey lunchmeat in hopes of inhibiting the L. monocytogenes cocktail. No reduction was observed.
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Barbier, Paul. "Diversité génomique des espèces bactériennes du genre Flavobacterium." Thesis, Evry-Val d'Essonne, 2013. http://www.theses.fr/2013EVRY0040/document.
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Les bactéries du genre Flavobacterium sont retrouvées dans des types d’habitats très divers. Ce genre contient trois espèces ichtyopathogènes : columnare, branchiophilum et psychrophilum qui est responsable de pertes économiques importantes pour l’élevage des salmonidés. Un projet de séquençage et de comparaison des génomes de plusieurs flavobactéries pathogènes de poissons ainsi qu’isolées de différents environnements a été mis en place pour améliorer les connaissances sur ce genre. Les objectifs étaient l’identification des déterminants de virulence et la caractérisation de différents marqueurs moléculaires des traits phénotypiques associés à leur mode de vie. L’analyse des génomes de F. psychrophilum a permis de mettre en évidence une diversité des structures chromosomiques au sein de l’espèce et d’identifier des cibles moléculaires prometteuses pour le développement de tests de diagnostic ainsi que des cibles vaccinales potentielles. Le génome de F. branchiophilum a permis d’identifier des mécanismes moléculaires de virulence originaux. Les caractéristiques du génome de F. indicum révèlent un mode de vie environnemental : sa petite taille et ses faibles capacités de dégradation des bio-polymères suggèrent que F. indicum est adapté à une niche écologique restreinte. Ces nouvelles données ont permis de caractériser in silico des marqueurs moléculaires de caractères phénotypiques. En particulier, un groupe de gènes (dnd) rare et responsable d’une modification étonnante de la molécule d’ADN a été décrit pour la première fois chez les Flavobacteriaceae. Ce projet a permis d’enrichir les connaissances sur les bactéries du genre Flavobacterium et a contribué au développement d’outils pour la santé animaleFlavobacterium species occur in a wide range of habitats. This genus includes three fish-pathogenic species, namely F. columnare, F. branchiophilum and F. psychrophilum. The latter is responsible for serious economic losses for salmonids farming in France and worlwide. A comparative genomics project including several fish-pathogenic flavobacteria as well as various environmental species has been set up in order to improve the knowledge on this poorly studied genus. Our aims were the identification of virulence determinants associated with pathogenicity and the characterization of various molecular elements reflecting phenotypes associated with their life-style. Analysis of the genomes of several F. psychrophilum isolates revealed the diversity of chromosomal structures within the species and identified in silico promising molecular targets for the development of diagnostic tests as well as potential vaccines targets. Analysis of the F. branchiophilum genome enabled to identify particular molecular virulence mechanisms. The features of the F. indicum genome reflected its environmental lifestyle : its small size and its limited bio-polymers degrading abilities suggested that F. indicum is adapted to a quite narrow ecological niche. These new data have allowed the in silico identification of many molecular elements reflecting phenotypic traits. In particular, a rare gene cluster (dnd) responsible for an unusual DNA structure modification was described for the first time within members of the family Flavobacteriaceae. This project enriched the knowledge on Flavobacterium species and contributed to the development of tools for animal health
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Haggarty, Jennifer. "Biofilm metabolomics : the development of mass spectrometry and chromatographic methodology for the analysis of dual-species pathogenic biofilms." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8616/.
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Polymicrobial diseases arise when multiple microorganisms colonize a host and form multi-species biofilms. Within polymicrobial communities bacteria, fungi, viruses and/or parasites directly and indirectly interact with one another in a multitude of ways. The composition and the interactions between organisms within polymicrobial biofilms govern disease severity and patient outcomes. Polymicrobial infections are of significant interest because of the escalating development of antimicrobial resistance and the increasing involvement polymicrobial biofilms in chronic and systemic infections. The Gram-positive bacteria Staphylococcus aureus and dimorphic fungi Candida albicans have been shown to coexist within the human host in polymicrobial biofilm communities which often result in increased disease severity and mortality. Both of these commensals are opportunistic human pathogens that cause a plethora of infections ranging from relatively non-lethal local infections to life-threatening systemic infections in immunocompromised individuals. S. aureus and C. albicans have been co-associated with a number of polymicrobial diseases including cystic fibrosis and polymicrobial sepsis. Furthermore, S. aureus and C. albicans dual-infections have been associated with increased virulence and antimicrobial resistance. Although an effort has been made to unravel the relationship between S. aureus and C. albicans, metabolomics offers a powerful analytical tool to gain a better understanding of the interactions between this bacteria and fungus. To gain a better understanding of these interactions novel methods must be developed to modulate biofilm growth. Metabolomics is intended to analyse the complete small molecule component of a biological system. Analytically, the diversity present in these compounds presents huge opportunities for improvement. The overall aim of this research was to develop novel metabolomics methods and to apply these methods to the analysis of a S. aureus/C. albicans dual species biofilm to aid in the understanding of the relationship between this bacteria and fungi. Characterisation of the S. aureus/C. albicans biofilm in comparison in to the mono-species was carried out using a number of techniques, including fluorescence microscopy, SEM imaging, qPCR and transcriptional analysis, which indicated that these two organisms interact with each other on a physical and molecular lever. Although the presence of C. albicans facilitates S. aureus biofilm formation in sera, the presence of the bacteria reduced the number of C. albicans within the dual-species biofilm compared to the fungal mono-species and caused ‘crinkled’ hyphae which suggested possible antagonistic behaviour towards the fungi. An untargeted liquid chromatography-mass spectrometry separation method was developed that effectively retained both polar and nonpolar compounds by serially coupling a reversed-phase liquid chromatography (RPLC) column to a hydrophilic interaction liquid chromatography (HILIC) column via a T-piece. Two independent pumps were incorporated into the system to allow independent gradient control of the two columns. The high dilution between the columns, achieved by the difference in flow rates, enabled the retention and separation of both polar and nonpolar standards and numerous polar and non-polar metabolites extracted from beer. Good peak shapes and retention time reproducibility was achieved across all compound classes analysed. Next, a targeted ion-chromatography mass-spectrometry method was developed for the analysis of central carbon metabolism intermediates, specifically those involved in glycolysis, the tricarboxylic acid (TCA) cycle and the Electron Transport Chain (ETC). A total mix of all of the energy metabolites standards analysed were able to be separated and detected using IC-MS, with the exception of DHAP, G3P, oxaloacetate, acetyl-CoA, succinyl-CoA, NAD and NADP. The method displayed good reproducibility and limits of detection. The complexity of the extracted biofilms proved challenging to the IC-MS. Sample variation and low intensities in some sample groups (particularly the S. aureus samples) resulted in lower detection than expected. The RPLC/HILIC method provided hundreds of metabolite detections, but suffered in comparison to the conventional HILIC method, likely due to far greater optimisation of the original technique, leading to the utilisation of the routine pHILIC method in place of the serially combined method. Untargeted metabolomics analysis highlighted significant changes in a number of metabolic pathways including purine, pyrimidine, methionine and cysteine metabolism between the S. aureus and C. albicans mono- species and the dual-species biofilms. The differences detected within individual pathways suggest a difference in behaviour when the microorganisms are cultured with one another. The dramatic downregulation of a large portion of essential metabolites within purine, pyrimidine, cysteine and methionine pathways is indicative of the bacteria struggling to proliferate and form strong biofilms in sera. Down-regulation of many of the pathways in the dual-species biofilm compared to the C. albicans mono-species biofilm suggests that the presence of S. aureus within the biofilm could be having an adverse effect on the C. albicans. The results and conclusions herein provide greater understanding of the clinically important interaction between S. aureus and C. albicans. Microscopic and molecular characterisation enabled visualisation of the dual-species biofilm. The development and application of metabolomics techniques highlighted changes in metabolism between the mono- and dual-species biofilms, indicating that the relationship between S. aureus & C. albicans may not be completely synergistic, as previously suggested. Although the metabolomics methods developed during this study performed well, with regards to the separation of simple standard mixes and the complex beer sample, were not suitable for biofilm analysis. Through continued sample preparation and chromatographic optimisation these novel methods could offer relatively simple alternatives to more time consuming and complex chromatographic procedures.
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Lam, Charlton. "Expression of Matrix Metalloproteinases in Naegleria fowleri and Their Role in Degradation of the Extracellular Matrix." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4962.
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Naegleria fowleri is a free-living amoeba found in freshwater lakes and ponds that is the causative agent of Primary Amoebic Meningoencephalitis (PAM). Matrix metalloproteinases (MMPs) have been described in protozoa, such as Plasmodium falciparum, Trypanosoma brucei, and Balamuthia mandrillaris, and have been linked to their increased motility and invasive capability by degrading components of the extracellular matrix (ECM). In addition, MMPs are often upregulated in tumorigenic cells and have been attributed as responsible for the metastasis of certain cancers. In the present study, in vitro experiments indicated that MMPs are linked functionally to the ECM degradation process. Gelatin zymography demonstrated protease activity in N. fowleri whole cell lysates, conditioned media, and media collected from in vitro invasion assays. Western immunoblotting confirmed the presence of the metalloproteinases MMP-2, -9, and -14. The highly virulent mouse-passaged amoebae expressed higher levels of MMPs than the weakly virulent axenically grown amoebae. The functional relevance of MMPs found in media in degradation of ECM components was confirmed through the use of MMP inhibitors. The collective in vitro results suggest that MMPs may play a critical role in the invasion of the CNS. Furthermore, the expression of select metalloproteinases may serve as amenable targets for therapeutic manipulation of expansive PAM.
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Mustafi, Sushmita. "Regulation of Rab5 GTPase activity during Pseudomonas aeruginosa-macrophage interaction." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/1016.
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Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen. Several antibiotic resistant strains of P. aeruginosa are commonly found as secondary infection in immune-compromised patients leaving significant mortality and healthcare cost. Pseudomonas aeruginosa successfully avoids the process of phagocytosis, the first line of host defense, by secreting several toxic effectors. Effectors produced from P. aeruginosa Type III secretion system are critical molecules required to disrupt mammalian cell signaling and holds particular interest to the scientists studying host-pathogen interaction. Exoenzyme S (ExoS) is a bi-functional Type III effector that ADP-ribosylates several intracellular Ras (Rat sarcoma) and Rab (Response to abscisic acid) small GTPases in targeted host cells. The Rab5 protein acts as a rate limiting protein during phagocytosis by switching from a GDP- bound inactive form to a GTP-bound active form. Activation and inactivation of Rab5 protein is regulated by several Rab5-GAPs (GTPase Activating Proteins) and Rab5-GEFs (Rab5-Guanine nucleotide Exchange Factors). Some pathogenic bacteria have shown affinity for Rab proteins during infection and make their way inside the cell. This dissertation demonstrated that Rab5 plays a critical role during early steps of P. aeruginosa invasion in J774-Eclone macrophages. It was found that live, but not heat inactivated, P. aeruginosa inhibited phagocytosis that occurred in conjunction with down-regulation of Rab5 activity. Inactivation of Rab5 was dependent on ExoS ADP-ribosyltransferase activity, and more than one arginine sites in Rab5 are possible targets for ADP-ribosylation modification. However, the expression of Rin1, but not other Rab5GEFs (Rabex-5 and Rap6) reversed this down-regulation of Rab5 in vivo. Further studies revealed that the C-terminus of Rin1 carrying Rin1:Vps9 and Rin1:RA domains are required for optimal Rab5 activation in conjunction with active Ras. These observations demonstrate a novel mechanism of Rab5 targeting to phagosome via Rin1 during the phagocytosis of P. aeruginosa. The second part of this dissertation investigated antimicrobial activities of Dehydroleucodine (DhL), a secondary metabolite from Artemisia douglasiana, against P. aeruginosa growth and virulence. Populations of several P. aeruginosa strains were completely susceptible to DhL at a concentration between 0.48~0.96 mg/ml and treatment at a threshold concentration (0.12 mg/ml) inhibited growth and many virulent activities without damaging the integrity of the cell suggesting anti-Pseudomonas activity of DhL.
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Taylor, Tiffany M. J. "Effect of Antimicrobials and Sodium Replacement Agents on the Survival of Pathogenic Bacteria in Low Sodium Low-Moisture Part-Skim (LMPS) Mozzarella Cheese." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1102.
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Recent increases in chronic cardiovascular diseases, such as hypertension, have put pressure on the food industry to reduce sodium levels. Dairy products, though full of vital nutrients, are perceived as being high in sodium. However, the reduction of salt in dairy products could potentially alter the microbial stability, as well as cause unfavorable changes in flavor. In order to reduce the sodium level, while maintaining acceptable flavor and microbial stability, salt replacers and alternative antimicrobial agents may need to be introduced into the food matrix. To identify potential antimicrobials for use in reduced sodium dairy products, this study evaluated the efficacy of eight commercially available antimicrobials in TSA, milk agar, and cheese agar. Antimicrobials included MicroGard 100, MicroGard 430, Nisaplin, NovaGard CB1, Protect-M, PuraQ Verdad RV75, SEA-i F75 and VMY1P. Antimicrobials were also tested in combination with six commercial sodium reduction agents (potassium chloride, Puracal PP/USP, Purasal Hi Pure P Plus, PuraQ Verdad NV10, SaltWise 0029 and SaltWise 1029) to if there were any interference with antimicrobial activity.
Antimicrobials with and without sodium reduction agents were added to the agar systems, then a five-strain cocktail of Listeria monocytogenes, Salmonella or Escherichia coli O157:H7 was spread plated at three concentrations: 101, 102 and 104 CFU/plate. Samples were then incubated at 35°C and observed for growth after 24 and 48h. SEA-i F75 was the most effective antimicrobial in each of the agars tested. Additionally, no interactions were observed between SEA-i F75 and any of the sodium replacement agents.
SEA-i F75 was selected for use in a final challenge study using six formulations of LMPS mozzarella cheese: regular sodium control cheese (1.7% NaCl, no antimicrobial added); low sodium control cheese (0.7% NaCl, no antimicrobial added); low sodium treated cheese (0.7% NaCl, treatment with SEA-i F75); low sodium cheese with KCl as salt replacer (0.7% NaCl, 1.0% KCl, treatment with SEA-i F75); low sodium cheese with Alta 2345 as salt replacer (0.7% NaCl, 0.25% Alta 2345, treatment with SEA-i F75); and low sodium cheese with Salona as salt replacer (0.7% NaCl, 0.95% Salona, treatment with SEA-i F75).
Fifteen gram cheese pieces from each formulation were dipped in an antimicrobial solution containing 0.25% SEA-i F75 then inoculated with L. monocytogenes, Salmonella, or E. coli O157:H7 at a target inoculum concentration of 102-103 CFU/g and incubated at either 4° or 12°C. In all trials, over all formulations and temperatures tested, initial decreases in counts, followed by organism recovery were observed. Therefore, SEA-i F75 was not effective at reducing the counts of pathogenic bacteria in LMPS mozzarella cheese.
Results from this study highlight the effect of the food matrix, and its components on antimicrobial efficacy. Future research includes examining the effect of one of the other antimicrobials in LMPS mozzarella cheese.
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Bellerose, Michelle M. "Genetic Identification of Novel Mycobacterium tuberculosis Susceptibility and Survival Mechanisms During Antibiotic Treatment." eScholarship@UMMS, 2020. https://escholarship.umassmed.edu/gsbs_diss/1081.
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Effective treatment of tuberculosis requires at least six months of combination therapy involving four antibiotics. Alterations in the physiological state of Mycobacterium tuberculosis during infection may reduce drug efficacy and prolong treatment, but these adaptations are incompletely defined. To investigate the mechanisms limiting antibiotic efficacy, I performed a comprehensive genetic study to identify M. tuberculosis genes and pathways important for bacterial survival during antibiotic treatment in vivo. First, I identified mutants in the glycerol kinase enzyme, GlpK, that promote survival under combination therapy. Similar glycerol catabolic mutants are enriched in extensively drug-resistant clinical isolates, indicating that these mutations may promote survival and the development of resistance in humans. A majority of these mutations are frameshifts within a homopolymeric region of the glpK gene, leading to the hypothesis that M. tuberculosis may reversibly produce drug-tolerant phenotypes through genetic variation introduced at homopolymer sites as a strategy for survival during antibiotic treatment. Second, I identified bacterial mutants with altered susceptibility to individual first-line anti-mycobacterial drugs. Many of these mutations did not have obvious effects in vitro, demonstrating that a wide variety of natural genetic variants can influence drug efficacy in vivo without altering standard drug-susceptibility tests. A number of these genes are enriched in drug-resistant clinical isolates, indicating that these genetic variants influence treatment outcome. Together, these data suggest new targets for improving therapy, as well as mechanisms of genetic adaptations that can reduce antibiotic efficacy and contribute to the evolution of resistance.
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Speaks, Tyler. "AlgR Directly Controls rsmA in Pseudomonas aeruginosa." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etd/2570.
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Pseudomonas aeruginosa is a bacterial pathogen that can infect any human tissue. The lungs of cystic fibrosis patients become chronically infected with Pseudomonas aeruginosa. Virulence factor gene expression is under elaborate regulatory control that remains poorly characterized. Understanding the regulatory hierarchy involved during infection is essential for identifying novel drug targets. RsmA is a post-transcriptional regulatory protein that controls expression of several virulence factors. Previous studies demonstrated alginate regulatory components AlgU and AlgR as regulators of rsmA expression. The aim of this study was to determine how AlgR controls rsmA expression. Western blot analysis of HA-tagged RsmA confirmed lower RsmA levels in an algR mutant. An electrophoretic mobility shift assay using purified AlgR demonstrated direct binding of AlgR to the rsmA promoter. These results indicate AlgR directly controls rsmA expression. We propose a mechanism whereby AlgR and AlgU work together to regulate rsmA.
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Etinosa, Omoruyi Beauty. "Immunological and molecular characterization of Cryptosporidium species in HIV-Positive and HIV-Negative diarrhoea patients in the Nkonkobe Municipality of the Eastern Cape Province of South Africa: a pilot study." Thesis, University of Fort Hare, 2010. http://hdl.handle.net/10353/392.
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Cryptosporidiosis is an infection caused by Cryptosporidium; a protozoan parasite that infects the gastrointestinal tract. The infection is of major public health concern in both developed and developing countries. Faecal samples were collected from 160 in-patient adults, with complaint of diarrhoea, admitted at Victoria hospital in Alice, Nkonkobe Municipality. Twenty apparently healthy subjects were included as controls. All diarrhoea positive patients were interviewed to record socio-demographic information, water supply and animal contact. Initial screening was carried out by microscopy and ELISA to detect positive Cryptosporidium. Genomic DNA was extracted from microscopically positive samples and a PCR reaction was perform to amplify the (18S) SSUrRNA gene for further identification and epidemiology of Cryptosporidium. Data were analysed using Pearson‘s χ2 and Fisher‘s exact test to assess the univariate association between Cryptosporidium infection and the possible risk factors. Of the 180 subjects screened for cryptosporidial infection, Cryptosporidium antigen was detected in 122 giving an overall prevalence of 67.8 percent. In HIV-positive diarrhoea patients, prevalence increased with ages; between 31-43 (mean age 36.5 yr) and 70-82 (mean age 75.8 yr) had a higher prevalence (100 percent) of the antigen than 18-30 (mean age 23.2 yr) and 83-95 (mean age 88.8 yr) (50.0 percent) in HIV-positive diarrhoea patients (P > 0.05). In HIV-negative diarrhoea patients, prevalence was highest in the 18-30 (mean age 23.2 yr) (87.5 percent) and least (35.7 percent) in those aged 83-95 (mean age 88.8 yr) (P > 0.05). Cryptosporidium antigen was higher in females than in males. Of 115 females (mean age 46.7yr) who participated in the study, antigen was detected in 90 (78.2 percent) against 32 (71.1 percent) of 45 males (mean age 42.6yr). None of the 20 apparently healthy control subjects was found to be infected with Cryptosporidium. Cryptosporidium was detected in 27 HIV-positive and 97 HIV-negative diarrhoea patients by any one of the techniques. Antigen detection by ELISA 14 showed the highest positivity 96 (76.8 percent) in HIV- negative and 26 (74.3 percent) in HIV- positive diarrhoea patients. PCR detected eighty-nine (71.2 percent) cases in HIV-negative and 23 (65.7 percent) in HIV-positive patients with diarrhoea. Only 13 (37.1 percent) HIV-positive and 34 (27.2 percent) HIV-negative diarrhoea patients were found positive for Cryptosporidium by modified ZN. No significant difference was observed in sensitivity of antigen detection by ELISA and PCR (96.9 percent) in HIV-negative diarrhoea patients, respectively. Specificity of the staining technique was 88.9 percent in HIV-positive and 96.6 percent in HIV-negative diarrhoea patients. No significant difference was found in specificity of antigen detection by ELISA and PCR in HIV-positive and HIV-negative diarrhoea patients, respectively. Positive predictive value of ZN staining in both HIV-positive and HIV-negative diarrhoea patients (92.3 and 96.9 percent) was statistically higher than ELISA and PCR. No significant difference was observed in negative predictive value of ZN technique for detection of Cryptosporidium between HIV-positive and HIV- negative diarrhoea patients. Differences found in prevalence rates due to water source, suggest that the high infection rates of specific groups are associated with their exposure to the contaminated water supply. The results indicate that Cryptosporidium infection is highly prevalent in adult faecal specimens in the Nkonkobe Municipality, an indication of active infection that is likely to emerge as major human pathogen in this location due to socioeconomic changes which favour transmission. However, sequencing analysis is required to differentiate between Cryptosporidium genotypes in the various outbreaks
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Poe, Tyler M., and Francine Marciano-Cabral. "Illumination of the Golgi apparatus of Pathogenic and Nonpathogenic Naegleria species." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6002.
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In this study, Naegleria fowleri, a pathogenic amoeba and the causative agent of Primary Amebic Meningoencephalitis (PAM), was utilized to determine the presence or absence of classically conserved Golgi molecules featured in the expression of a Golgi apparatus. Previous studies concluded no Golgi expression via light microscopy and transmission electron microscopy, but a recent report on Naegleria gruberi indicated the presence of dispersed Golgi tubules. Non-pathogenic species of the Naegleria genus such as Naegleria gruberi 30540 and Naegleria lovaniensis 30569 were utilized in Western immunoblot analysis compared to reduced whole-cell lysate proteins of two strains of N. fowleri and Vero CCL-81, Chlorocebus sp. kidney epithelial cells, which were utilized as a positive control for Golgi expression. N. fowleri and N. lovaniensis whole-cell lysates had indications of a 110 kDa reduced protein, associated with the predicted molecular weights of the beta-COPI subunit of the COPI cis-Golgi vesicular transport complex with further Western immunoblot indication of a weak band around 25 kDa corresponding to rabbit polyclonal antibodies specific for ARF1. Serial Dilutions of Wheat Germ Agglutinin Alexa Fluor 488TM were performed on Vero cells, Naegleria fowleri 30894, and N. gruberi 30540 with 1:100 dilution of recommended stock dilution of WGA 488 determined for utilization in sequential immunofluorescence. Sequential immunofluorescence with Wheat Germ Agglutinin Alexa Fluor 488TM and then blocked with 3% BSA:PBS [wt/vol] dilution with subsequent incubation in rabbit anti-beta-COPI primary 1:250, and 1:1000 of Alexa Fluor 594 goat anti-rabbit secondary antibody exposure showed strong indications of organized cis- and trans-punctate Golgi body markers in close association in individual and dividing cells of Naegleria fowleri and conserved Golgi expression in the positive control Vero cells, but further experiments are necessary to verify this finding with N. fowleri.
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Vanover, Jennifer. "Herpes Simplex Virus Glycoprotein D/Host Cell Surface Interaction Stimulates Chlamydia trachomatis Persistence via a Novel Pathway." Digital Commons @ East Tennessee State University, 2008. https://dc.etsu.edu/etd/2019.
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When presented with certain unfavorable environmental conditions, C. trachomatis reticulate bodies (RBs) enter into a viable, yet noncultivable state called persistence. Two hallmarks of persistent chlamydiae are swollen, aberrantly shaped RBs, as viewed by transmission electron microscopy and a decrease in infectious progeny. Several models of chlamydial persistence have been described, including interferon-γ (IFN-γ), IFN-α, IFN-β, and tumor necrosis factor-α-exposure and nutrient deprivation. Previously, we established an in vitro co-infection model of two of the most common sexually transmitted pathogens in the United States, C. trachomatis and Herpes Simplex Virus-2 (HSV). Data from this tissue culture model indicate that: i) viral co-infection stimulates the formation of persistent chlamydiae and ii) productive HSV replication is not required for persistence induction. Further studies indicate that, co-infection-induced persistence is not mediated by: i) any known anti-chlamydial cytokine; ii) activation of inducible nitric oxide synthase or indoleamine 2, 3-dioxygenase; iii) inhibition of vesicular trafficking or sphingomyelin transport to the inclusion or; iv) amino acid, iron or glucose deprivation. These data demonstrate that co-infection-induced persistence is mediated by a previously undescribed, novel mechanism. During long-term co-infection with UV-inactivated HSV-2, chlamydiae recover following an initial suppression of chlamydial infectivity. These data indicate that HSV-induced persistence, like other persistence models, is reversible. Co-incubation of fixed, HSV-2-infected inducer cells with viable, C. trachomatis infected responder cells suppresses production of infectious chlamydial progeny and stimulates the formation of swollen, aberrantly shaped RBs. Antibody neutralization of HSV glycoprotein D (gD), which prevents viral attachment to one of four known HSV co-receptors on the host cell surface, also prevents co-infection-induced persistence, suggesting that HSV gD interaction with host cell surface receptors can provide the necessary stimulus to alter C. trachomatis development. Finally, exposure of C. trachomatis infected cells to soluble, recombinant HSV-2 gD:Fc fusion proteins decreases production of infectious EBs to a similar degree observed in co-infected cultures. Thus, we hypothesize that interaction of HSV gD with the host cell surface triggers a novel host anti-chlamydial pathway that restricts chlamydial development.
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Stuffle, Derek. "Two Component Pathway Regulation of Transport Genes Involved in Quorum Sensing and Response to Bacterial Signaling Molecules in C. albicans." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etd/3373.
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The morphogenesis of C. albicans is a major aspect of its virulence and is regulated by quorum sensing (QS) molecules they produce, as well as the presence of neighboring microbes.Two mutant transporters, SSU1 and CDR4, were characterized for their ability to form biofilms in the presence of cyclic-di-GMP and 3-oxo-12-homoserine lactone. While homoserine lactone showed a decrease in biofilm density of both mutants compared to the wild-type strain, wild-type and ssu1 biofilm densities increased considerably in the presence of cyclic-di-GMP while testing lower inocula. Additionally, it has been shown that C. albicans mutants lacking the hybrid histidine kinase, Chk1, are refractory to the effects of farnesol, a QS molecule that inhibits morphogenesis.We determined both CDR4 and SSU1 expression is reduced or highly repressed in the chk1, ypd1, and skn7 null strains. Our results suggest these two genes are downstream targets in a pathway regulated by Chk1p.
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Cameron, Michelle. "Impact of low-frequency high-power ultrasound on spoilage and potentially pathogenic dairy microbes." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/597.
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Wallace, Joanne Sarah. "The effects of light and other abiotic factors on the survival of the indicator bacteria Escherichia coli and Klebsiella pneumoniae and the pathogenic bacteria : Campylobacter jejuni and Salmonella enteritidis." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240484.
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Zincke, Diansy. "Characterization of the poxAB Operon Encoding a Class D Carbapenemase in Pseudomonas aeruginosa." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1794.
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Pseudomonas aeruginosa is a dreaded opportunistic pathogen that causes severe and often intractable infections in immunocompromised and critically ill patients. This bacterium is also the primary cause of fatal lung infections in patients with cystic fibrosis and a leading nosocomial pathogen responsible for nearly 10% of all hospital-acquired infections. P. aeruginosa is intrinsically recalcitrant to most classes of antibiotics and has the ability to acquire additional resistance during treatment. In particular, resistance to the widely used β-lactam antibiotics is frequently mediated by the expression of AmpC, a chromosomally encoded β-lactamase that is ubiquitously found in P. aeruginosa strains. This dissertation delved into the role of a recently reported chromosomal β-lactamase in P. aeruginosa called PoxB. To date, no detailed studies have addressed the regulation of poxB expression and its contribution to β-lactam resistance in P. aeruginosa. In an effort to better understand the role of this β-lactamase, poxB was deleted from the chromosome and expressed in trans from an IPTG-inducible promoter. The loss of poxB did not affect susceptibility. However, expression in trans in the absence of ampC rendered strains more resistant to the carbapenem β-lactams. The carbapenem-hydrolyzing phenotype was enhanced, reaching intermediate and resistant clinical breakpoints, in the absence of the carbapenem-specific outer membrane porin OprD. As observed for most class D β-lactamases, PoxB was only weakly inhibited by the currently available β-lactamase inhibitors. Moreover, poxB was shown to form an operon with the upstream located poxA, whose expression in trans decreased pox promoter (Ppox) activity suggesting autoregulation. The transcriptional regulator AmpR negatively controlled Ppox activity, however no direct interaction could be demonstrated. A mariner transposon library identified genes involved in the transport of polyamines as potential regulators of pox expression. Unexpectedly, polyamines themselves were able induce resistance to carbapenems. In summary, P. aeruginosa carries a chromosomal-encoded β-lactamase PoxB that can provide resistance against the clinically relevant carbapenems despite its narrow spectrum of hydrolysis and whose activity in vivo may be regulated by polyamines.