To see the other types of publications on this topic, follow the link: Periodontitis Drug resistance in microorganisms.
Dissertations / Theses on the topic 'Periodontitis Drug resistance in microorganisms'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Periodontitis Drug resistance in microorganisms.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Roe, Darcie Elizabeth. "Prevalence and mechanisms of antibiotic resistance in oral bacteria." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9310.
Full text
2
Laxminarayan, Ramanan. "Economics of antibiotic resistance /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/7412.
Full text
3
Abrahem, Abrahem F. "Mechanisms of drug resistance in malaria." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0033/MQ50704.pdf.
Full text
4
Dodgen, Taylor L. "Escherichia coli and Antibiotic Resistance to Tetracycline Antibiotics." Lynchburg, Va. : Liberty University, 2008. http://digitalcommons.liberty.edu.
Full text
5
Joseph, Renu. "Evolution of multiple antimicrobial drug resistance conservation of genes encoding streptomycin, sulfonamide and tetracycline resistance among Escherichia coli with increasing multi-drug resistance /." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/R_Joseph_111707.pdf.
Full text
6
Ho, Pak-leung, and 何柏良. "Emerging antimicrobial resistance in Streptococcus pneumoniae." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41290999.
Full text
7
Ho, Pak-leung. "Emerging antimicrobial resistance in Streptococcus pneumoniae." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41290999.
Full text
8
Wong, Kin-man Gilman. "Antibiotic resistance in laribacter hongkongensis." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182347.
Full text
9
Grubbs, Joseph R. "The effects of Triclosan derivatives against the growth of Staphylococcus Aureus." Lynchburg, Va. : Liberty University, 2008. http://digitalcommons.liberty.edu.
Full text
10
Egervärn, Maria. "Antibiotic resistance in Lactobacillus reuteri and Lactobacillus plantarum /." Uppsala : Swedish University of Agricultural Sciences, 2009. http://diss-epsilon.slu.se/archive/00002017/01/Acta_Thesis%2C_Egerv%C3%A4rn_090508.pdf.
Full text
11
Certad, Gabriela. "Characterization of drug-resistant isolates of Plasmodium falciparum." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0017/MQ37102.pdf.
Full text
12
Eby, Anne Kathryn. "Factors affecting medical-surgical area nurses' compliance with contact precautions." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/eby/EbyA1209.pdf.
Full textAbstract:
Multidrug-resistant organisms are a significant threat in health care facilities, and are associated with many adverse consequences for infected patients. However, despite these concerns and the evidence that contact precautions are an effective way to address them, compliance with contact precautions guidelines among health care workers remains low (Farr, 2000). The primary goal of this study was to examine factors affecting medical-surgical nurses' compliance with contact precautions guidelines when caring for patients colonized by or infected with multidrug-resistant organisms. A secondary purpose of this study was to describe demographic characteristics of medical-surgical nurses to determine if certain characteristics (e.g. age, time in practice, level of education) had a relationship with their compliance in using contact precautions guidelines. Finally, this study examined barriers to the use of contact precautions and consequences for failure to follow contact precautions guidelines. A survey tool was developed by the researcher for this study to examine these questions, and an exploratory, cross-sectional, correlation descriptive study was conducted. The study group was made up primarily of female nurses with associate or bachelor degrees. Nurses from the orthopedic and neurosurgery unit made up the largest percentage of respondents. All respondents indicated that they were familiar with CP guidelines. Eight primary barriers to the use of contact precautions were listed by participants. Half of the participants listed one of the time management categories ("no time" or "urgency") as the primary barrier to compliance with contact precautions. Participants' age, years experience and level of education were not statistically significant predictors of the participants' level of compliance. There was not a statistically significant difference between the barriers to compliance groups (no time/urgency versus other) on their ability to comply with contact precautions. Lastly, there was not a statistically significant relationship among the primary consequence of non-compliance with CP guidelines (medical versus other) and the participants' level of compliance (low versus high).
13
Wong, Chun-wai. "Antimicrobial resistance in Escherichia coli isolated from food animals and humans." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557935.
Full text
14
Yu, Chun Wing. "Potent divalent vancomycins against vancomycin resistant enterococci (VRE) /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202002%20YU.
Full textAbstract:
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 71-76). Also available in electronic version. Access restricted to campus users.
15
Knapp, van Bogaert Donna. "Earth, air, fire and water : moral responsibility and the problem of global drug resistance." Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49936.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2004.ENGLISH ABSTRACT: In this dissertation, I grapple with the problem of global drug resistance and moral responsibility which, as far as I am aware, has so far not been presented as a topic of ethical inquiry. It represents a conundrum involving three major factors: microbial adaptation and change, human social factors and environmental changes. Drug resistance is a phenomenon in which certain microorganisms, when exposed to antimicrobial agents, may acquire the beneficial trait of drug resistance which ensures a better potential for their survival. The acquired trait of drug resistance I argue renders such microorganisms 'supra-natural '. Supra-natural is a term I coin for entities that have been imposed upon nature by human design; they do not follow the natural evolutionary processes of adaptation and change. Drug resistance is classified as an emerging infectious disease. Human social factors and environmental change (particularly population growth, density and consumerist practices) enhance the rise of emerging infectious diseases. Through such increasing destructive practices, stress is placed on the environment. Environmental stress facilitates the rise of new and old infectious diseases and the spread of drug resistant supra-natural microorganisms. Thus, our ability to treat successfully illnesses and injuries in humans, animals and plants is increasingly impaired. Morally, we are responsible for the problem of global drug resistance. Drug resistant microorganisms exist in nature and concerning this, we can do nothing. At best, we can only try to control the problem using prudential measures. The problem of global drug resistance represents both a biomedical ethical and an environmental ethical issue. Is there a way out of the human-nature debate? Through Bryan Norton's enlightened anthropocentrism, I identify the ways in which his thesis may be applied to the problem of human and environmental concerns and show its applicability in broadening the parameters of biomedical ethics education to include environmental concerns. Key words: biomedical ethics, environmental ethics, drug resistance, Supra-natural' microorganisms, ethics education, enlightened-anthropocentrism.
AFRIKAANSE OPSOMMING: In hierdie proefskrif bespreek ek die probleem van die verskynsel dat mikroorganismes op 'n globale skaal weerstand begin bied teen mediese middels (globale middel-weerstandigheid) en die morele verantwoordelikheid wat dit oproep - 'n probleem wat, na my beste wete, nog nooit aangebied is as 'n tema van etiesfilosofiese ondersoek nie. Dit verteenwoordig 'n kompleks van drie belangrike oorwegings: mikrobiese aanpassings en veranderinge, menslike sosiale faktore, en omgewingsveranderinge. Middel-weerstandigheid is 'n verskynsel waarin sekere mikro-organismes, wanneer hulle blootgestel word aan antimikrobiese agente, die (vir hulself) voordelige kenmerk kan bekom van weerstandigheid teen die middel; iets wat 'n beter potensiaal vir hul eie oorlewing verseker. Hierdie bekomde kenmerk (middel-weerstandigheid) maak, volgens my argument, sulke mikro-organismes 'supra-natuurlik'. Supra-natuurlik is 'n term wat ek munt vir entiteite wat aan die natuur blootgestel is as gevolg van menslike ontwerp; hulle volg nie die natuurlike evolusionêre prosesse van adaptasie en verandering nie. Middel-weerstandigheid word geklassifiseer as 'n opkomende aansteeklike siekte. Menslike sosiale faktore en omgewingsveranderinge (veral bevolkingsgroei, -digtheid and verbruikerspraktyke ) vergroot die opkoms van aansteeklike siektes. Deur sodanige toenemende destruktiewe praktyke word stres geplaas op die omgewing. Omgewingstres fasiliteer die opkoms van nuwe en ou aansteeklike siektes asook die verspreiding van weerstandige supra-natuurlike mikro-organismes. Ons vermoë om siektes en beserings van mense suksesvol te behandel, word gevolglik toenemend ondermyn. Moreel gesproke is ons verantwoordelik vir die probleem van globale middelweerstandigheid. Middel-weerstandige mikro-organismes bestaan in die natuur, en aan daardie feit as sodanig kan ons niks doen nie. Ons kan, ten beste, probeer om die probleem te beheer deur middel van verstandige maatreëls. Die probleem van globale middel-weerstandigheid verteenwoordig sowel 'n biomedies-etiese as 'n omgewingsetiese kwessie. Is daar 'n uitweg uit die mens-natuur debat? Ek identifiseer, met 'n beroep op Bryan Norton se swak antroposentrisme, maniere waarop sy tese toegepas sou kon word op die probleem van menslike en omgewingsoorgwegings Ek wys ook op die toepaslikheid daarvan vir die verbreding van die parameters van biomediese etiek-opvoeding ten einde omgewingsoorwegings deel van lg. te maak. Kembegrippe: biomediese etiek, omgewingsetiek, middel-weerstandigheid, 'Supra- . natuurlike' mikro-organismes, etiek-opvoeding, swak antroposentrisme.
16
Ho, Siu-leuk, and 何笑略. "Development of genotypic resistance testing for integrase inhibitor." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45446386.
Full text
17
Wong, Kin-man Gilman, and 黃健文. "Antibiotic resistance in laribacter hongkongensis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182347.
Full text
18
Wong, Chun-wai, and 黃振威. "Antimicrobial resistance in Escherichia coli isolated from food animals and humans." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557935.
Full text
19
Ellis, Lucy C. J. "Human and rat multidrug resistance-associated proteins (MRP/Mrp)." Thesis, University of Aberdeen, 2010. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=128325.
Full textAbstract:
The multidrug resistance associated proteins (MRP(human)Mrp (rat) are ATP-dependent transporters responsible for the efflux of a wide range of substrates, including endogenous compounds e.g. bilirubin, drug metabolites e.g. paracetamol glucuronide and fluorescent dyes e.g. 5 (and 6)-carboxy-2’,7’-dichlorofluorescein (CDF). Mrp1-6 (abccl-6) are expressed in rat liver, with Mrp2 being expressed at the highest level. Isolation of hepatocytes by in situ collagenase perfusion causes bile canalicular disruption and internalisation of Mrp2. Cells cultured in a sandwich configuration of Matrigel or collagen (Type 1) showed bile canalicular reformation at different days in cell culture, depending on the extracellular matrix and time of overlay. We have developed a method for quantifying Mrp-mediated efflux in hepatocytes cultured in a sandwich configuration of collagen (Type 1). This method is unique in its ability to distinguish between sinusoidal efflux, canalicular efflux and diffusion in intact hepatocytes. Alternative in vitro models of Mrp2-mediated efflux include the vesicular (direct and indirect methods) and the ATPase assays. We have used these assays to identify atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin as substrates of human and rat MRP2/Mrp2. A close correlation was seen between the kinetic parameters of transport of the Mrp2 substrate; CDF determined in sandwich cultured rat hepatocytes using the method above (Km = 3.5 – 9.9 μM), vesicle preparations (Km = 37.9 μM) and membrane preparations (Km = 18.7 μM). We also present data to implicate the nuclear receptors, PXR, CAR and FXR in the regulation of abcc2 and abcc3 and PXR and CAR in abcc1 gene regulation. Abcc2 and abcc5 are also up-regulated in response to a toxic insult to the cell, probably via Nrf2 activation, suggesting a role in cell defence.
20
Meiring, Jillian A. "Antimicrobial resistance patterns in a Port Elizabeth hospital." Thesis, Rhodes University, 1993. http://hdl.handle.net/10962/d1004104.
Full textAbstract:
Antibiotic resistance in clinical bacterial isolates remains an ongoing problem requiring continuous monitoring to effect some form of control. Comparative studies have not been previously reported for the Eastern Cape Region, South Africa and this study was undertaken to monitor resistance patterns in clinical isolates from Provincial Hospital, Port Elizabeth. Over the three year period 1989 to 1991, 9888 susceptibility results from isolates examined in the SAIMR pathology laboratory were analysed and collated using a stand-alone computer program. Resistance patterns for a range of nineteen antibiotics were collated for isolates from various sampling points within the hospital. Results were reported as resistance patterns in individually isolated species. Levels of resistance in each species were compared to those reported from South Africa and abroad, and changing patterns of resistance were noted within the three year period at the Provincial Hospital, Port Elizabeth.
21
Smith, Lisa Marie. "Antibiotic resistance and coliform bacteria in the Ohio River; 2002 to 2004." Huntington, WV : [Marshall University Libraries], 2006. http://www.marshall.edu/etd/descript.asp?ref=679.
Full textAbstract:
Theses (M.S.)--Marshall University, 2006.Title from document title page. Includes abstract. Document formatted into pages: contains vii, 73 p. including illustrations and maps. Bibliography: p. 25-28.
22
To, Pui-chi Amanda, and 杜佩芝. "Molecular epidemiology of erythromycin resistance in Streptococcus bovis and lancefield group G beta-hemolytic streptococci andhorizontal gene transfer of antibiotic resistance genes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29387401.
Full text
23
Ho, Wing-yin Queenie, and 何穎賢. "Antimicrobial use & resistance in China: implications for public health in Hong Kong : an exploratoryanalysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46937092.
Full text
24
Lo, Pui-ying. "Molecular epidemiology and antimicrobial resistance of methicillin resistant Staphylococcus aureus blood culture isolates." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B44192885.
Full text
25
Lo, Pui-ying, and 盧珮瑩. "Molecular epidemiology and antimicrobial resistance of methicillin resistant Staphylococcus aureus blood culture isolates." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44192885.
Full text
26
Howe, Whitney M. "The mechanism of gene expression regulation by the ykkCD putative riboswitch." Muncie, Ind. : Ball State University, 2009. http://cardinalscholar.bsu.edu/652.
Full text
27
Léger, Jean-François. "Effects of chloramphenicol on Pseudomonas aeruginosa." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60549.
Full textAbstract:
The characteristics of the effects of chloramphenicol on Pseudomonas aeruginosa were examined. Resistant strains were easily isolated following a single passage in chloramphenicol at 150 $ mu$g/ml to 500 $ mu$g/ml. Drug detoxification or altered sensitivity of the target site could not be the mechanism of resistance. This resistance to chloramphenicol was correlated with the addition of an outer membrane protein with a molecular weight of 49 kDa and the loss of two outer membrane proteins, one with the molecular weight of 19 kDa and the other of about 10 kDa. The highly specific requirement of the resistant strains for Ca$ sp{2+}$, Mg$ sp{2+}$, Mn$ sp{2+}$ or Sr$ sp{2+}$ described by Irvin and Ingram (1982) was confirmed by the observation that the outer membrane of the resistant cells contained twice as much Mg$ sp{2+}$ cation as the sensitive cells. Many other experiments designed to observe the effects of chloramphenicol on the outer membrane of P. aeruginosa failed. It was concluded that the observations made in this study strongly suggested a "re-structuring" of the outer membrane of P. aeruginosa, rendering the resistant cells more impermeable to chloramphenicol.
28
Lo, Chiu-sing. "Territory-wide Antibiotic Stewardship Programme and its effectiveness in public hospitals in Hong Kong." View the Table of Contents & Abstract, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38478626.
Full text
29
Li, Zhen, and 李珍. "Molecular epidemiology of carbapenem-resistant enterobacteriaceae." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B5016286X.
Full textAbstract:
Dissemination of Carbapenem-Resistant Enterobacteriaceae (CRE) has raised a new challenge for health organizations all over the world. Acquisition of carbapenemase genes is the most worrisome among these CRE isolates.
This study was constructed to investigate the dissemination of CRE isolates in Hong Kong and also to characterize plasmids harboring carbapenemase genes.
CRE isolates were collected from public hospitals in Hong Kong from August 2006 to June 2012. Antimicrobial susceptibility of all CRE isolates was tested using disc diffusion method. Screening of carbapenemase genes (blaNDM , blaKPC, blaIMP, blaVIM and blaOXA-48) and ESBL genes (blaCTX-M and blaSHV) were also performed. Clonal relatedness was studied by multi-locus sequence typing. Characterization of plasmids was carried out by conjugation, S1-PFGE, hybridization and plasmid replicon typing.
A total of 69 CRE isolates were collected including 50 K. pneumoniae, 15 E. coli, 2 E. cloacae, 1 E. aerogenes and 1 C. freundii. Eighteen carbapenemase producing Enterobacteriaceae were isolated from different patients with travel histories among these 69 isolates. Four K. pneumoniae were detected to carry blaKPC genes on different transferable plasmids as follows: 50 kb, IncX3 plasmid (ST258); 70 kb, un-typeable plasmid (ST258); 130 kb, un-typeable plasmid (ST11) and 140 kb, un-typeable plasmid (ST11). blaIMP genes were also detected in four CRE isolates to be harbored by different plasmids or located on chromosome: ST11 K. pneumoniae (50 kb, IncN), ST1 K. pneumoniae (150 kb, IncA/C), E. cloacae (130 kb, IncN-L/M) and ST899 K. pneumoniae (chromosomal located).
NDM-1 (New Delhi Metallo enzyme) producing E. coli (n = 5), K. pneumoniae (n = 2), E. aerogenes (n = 1), E. cloacae (n = 1) and C. freundii (n =1) were also found in this study. Eight of them were isolated from patients travelled to different provinces of China blaNDM-1 was found to be carried by transferable plasmids in all ten isolates: IncX3 (n = 7, 50 kb), IncL/M (n = 1, 88 kb), IncA/C2 (n = 1, 140 kb) and FIIY- FIBS (n = 1, 110kb). Six of the seven IncX3 plasmids showed identical digestion profile while the other one only had two bands different from others using Restriction fragment length polymorphism (RFLP) analysis.
An IncX3 plasmid pNDM-HN380 from a K. pneumoniae strain CRE380 was completely sequenced using Genome Sequencer FLX (Roche, USA). pNDM-HN380 was a 54,035 bp circular plasmid with 52 open reading frames (ORFs). The backbone of pNDM-HN380 was identical to those previous described IncX plasmids pIncX-SHV (accession number JN247852) and pEC14_35 (accession number JN935899). The blaNDM-1 gene was carried on an ISAba125 and IS26 flanked transposon-like element. And this element except IS26 and an interrupted ISAba125 was found to be identical to pNDM-BJ01 (accession number JQ001791).
In conclusion, this is the first we describe a blaNDM-1 carrying IncX3 plasmid. This IncX3 plasmid was found to be predominant in the dissemination of blaNDM-1 in China. Future study of the nationwide dissemination of carbapenemase genes and also the novel IncX3 plasmids is needed.published_or_final_version
Microbiology
Master
Master of Philosophy
30
Ho, Yat-man Alex, and 何逸敏. "Molecular epidemiology of multidrug-resistant Acinetobacter baumannii." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/197078.
Full textAbstract:
Acinetobacter baumannii is an important nosocomial pathogen worldwide because of its remarkable ability to acquire antibiotic resistance. The global emergences of multidrug-resistant A. baumannii (MDR-AB) clones are predominated by a number of widely disseminated clones, namely clonal complex (CC) 1, CC2, and CC3. In early 2010, we reported two major clones of MDR-AB, designated HKU1 and HKU2 belong to sequence types (ST) 96 and ST92, widely disseminating in our hospitals. ST92 is a predominant clone that is prevalent in more than 30 countries, whereas ST96 has been identified recently and is geographically confined to certain parts of China. Our previous study only investigated the isolates collected in the year 2005-2006. We therefore extended our investigation over a six-year period (2005-2010) to generate a more complete picture of the molecular epidemiology and resistance mechanisms in A. baumannii.
Firstly, we performed the susceptibility test on various antimicrobial agents and employed molecular methods to characterize the epidemiology of the target A. baumannii isolates. For the entire study period, increased resistance rates were noted for the seven antimicrobial agents, namely imipenem, piperacillin-tazobactam, cefoperazone, ticarcillin-clavulanate, ciprofloxacin, gentamicin and amikacin (P <0.01). Worryingly, an increased trend was also observed for the pandrug-resistant rate, from 0.2% in the year 2005-2006, to 1.9-2.9% in the year 2007-2008 and up to 6.0-8.1% in the year 2009-2010 (chi square for trend, P <0.001). Pulsed-field gel electrophoresis and multilocus sequence typing (PFGE/MLST) categorized 100 out of 108 (92.6%) isolates into four clones (PFGE/MLST), namely HKU2/ST92 (n = 14), HKU3/ST254 (n = 73), HKU4/ST137 (n = 5), and HKU5/ST362 (n = 8), respectively. PCR showed that 88.9% (96/108) of the amikacin-resistant isolates were armA positive and all isolates were found to harbour at least one of the OXA-type carbapenemases with frequencies as follows: OXA-51-like (98/108, 90.7%), OXA-23-like (85/108, 78.7%), OXA-58-like (9/108, 8.3%) and OXA-24-like (8/108, 7.4%).
Secondly, we compared the biological fitness of the circulating clones by performing the doubling time and adhesion experiment. The results demonstrated that HKU3/ST254 has a higher capability for replication and adherence to human bronchial epithelial cells. Together with the higher antibiotic resistance rate, the selective advantages in terms of biological fitness may facilitate the clonal expansion and wide dissemination of this lineage.
Finally, whole genome sequence data showed a high amount of resistance genes intermixed with various insertion sequence (IS) elements, integrons and transponsons clustering inside the resistance islands. The presence of a second genomic resistance island conferring aminoglycoside and sulphonamide resistance, additional loci outside the resistance islands harbouring resistance genes and the high amount of antibiotic efflux pumps in various A. baumannii genomes demonstrated that resistance islands contribute a significant part to the multidrug-resistant phenotype in A. baumannii but are not the only factor. The correlation analysis further demonstrated the significance of IS elements in the dissemination of antibiotic resistance genes in the A. baumannii genomes. As a whole, whole genome sequence data may provide an informative and efficient approach to generating a more comprehensive picture to study the resistance mechanism of the epidemic strains.published_or_final_version
Microbiology
Doctoral
Doctor of Philosophy
31
Crawford, Patrick Anthony. "Characterization of ImiS, the metallo-[beta]-lactamase from Aeromonas veronii bv. sobria." Oxford, Ohio : Miami University, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1069106986.
Full textAbstract:
Thesis (Ph. D.)--Miami University, Dept. of Chemistry and Biochemistry, 2003.Title from first page of PDF document. Document formatted into pages; contains xi, 150 p. : ill. Includes bibliographical references.
32
McKay, Geoffrey A. "Characterization of aminoglycoside phosphotransferase APH(3')-IIIa : an enterococcal enzyme conferring resistance to aminoglycoside antibiotics /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0034/NQ66223.pdf.
Full text
33
Morgan, Marcella Alexandra. "Antimicrobial resistance in Staphylococcus aureas." Scholarly Commons, 1988. https://scholarlycommons.pacific.edu/uop_etds/2147.
Full textAbstract:
Susceptibility of 112 strains of Staphylococcus aureus obtained from Dameron Hospital, Stockton, California was tested with 18 antimicrobials . The MIC method was used with the following antimicrobials : tetracycline, oxacillin, penicillin, ampicillin, vancomycin, cefazolin, erythromycin, clindamycin, gentamycin, rifampin, trimethoprimsulfamethoxazole, chloramphenicol, and cefotaxime . The standard Kirby-Bauer disc diffusion method was used to test neomycin, tobramycin, and amikacin . Methicillin, oxacillin, and nafcillin were tested with a modified Kirby-Bauer method, which included the addition of a 4% salt supplement to the media, incubation at 32C, and readings at both 24 and 48 hours. Comparing results of this study with those of Hall (1975), suggested that resistance to the following antibiotics has increased: penicillin, ampicillin, erythromycin, neomycin, gentamycin, methicillin, oxacillin, nafcillin, cefazolin, and clindamycin . Resistance to tetracycline has decreased. No resistance to chloramphenicol or vancomycin was encountered in either study . Of the 112 strains studied, 13 . 4% were susceptible to all antibiotics tested. Twelve patterns of resistance were identified : 0 . 9% were resistant to neomycin only, 1.8% to erythromycin only, 63.9% to both penicillin and ampicillin, and 20 . 0% were multiply- resistant . Nine patterns of multiple-resistance were found, involving a minimum of three antibiotics and a maximum of nine . Three MRSA strains were identified from out-patient isolates; no in-patient isolates were methicillin-resistant . The study suggests that MRSA strains are not a problem at Dameron Hospital, but identification of this group would be more accurate if incubation of the MIC panels is maintained for at least 24 hours at ~35C . It was found that the MIC method of antimicrobial susceptibility testing is more reliable than the Kirby-Bauer disc diffusion method for detection of methicillin-resistance. Problems involved in identification of heteroresistant staphylococci are discussed .
34
Wan, Hok-him, and 尹學謙. "Geographical analysis of the epidemiology of antibiotic resistance in Streptococcus pneumoniae in Europe: y Wan HokHim." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B50223112.
Full textAbstract:
Objective: To find out the spatial autocorrelation of antibiotic resistance of S. pneumonia and test the significance of distance as a risk factor.
Methods: Descriptions of penicillin and macrolide resistance in EARS-Net countries from 2006 to 2010 were given. Global moran’s I and Anselin moran’s I were used to assess the spatial autocorrelation and gravity model was used to test the significance of distance and other socio – economic factors.
Results: The trend of resistance in Europe was stable. Positive spatial autocorrelation existed from 2006 to 2010 for penicillin (Z(I): 0.16-0.2) and 2009 to 2010 for macrolide (Z(I): 0.11 -0.13). Some clusters (hotspots) were identified; they were Cyprus (2006-2010 for penicillin and 2009 to 2010 for macrolide), Spain (2006 for penicillin), France (2006 for penicillin), Romania (2009 for penicillin and macrolide) and Bulgaria (2009 for penicillin and macrolide). The result of gravity model showed that only parameters of population in 2007 for penicillin (p<0.05) and parameter of distance in 2009 for penicillin (p<0.05) in Cyprus were statistically significant.
Conclusion: Distance was not a risk factor of high prevalence of antibiotic resistance of S. pneumoniae although there was a positive spatial autocorrelation. Improvement in surveillance system and appropriate public action were recommended for controlling the spread of resistant strain of S. pneumoniae.published_or_final_version
Public Health
Master
Master of Public Health
35
Kwok, Chi-fong Joyce. "Macrolide-lincosamide-streptogramin B resistance among staphylococcus aureus carried by children with atopic dermatitis /." View the Table of Contents & Abstract, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39401182.
Full text
36
Kwok, Chi-fong Joyce, and 郭志芳. "Macrolide-lincosamide-streptogramin B resistance among staphylococcus aureus carried by children with atopic dermatitis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B45011552.
Full text
37
Levings, Renee S. "Detailed molecular analysis of antibiotic resistance regions within a collection of multi-drug resistant Salmonella spp. from Australian sources." Department of Biological Sciences - Faculty of Science, 2008. http://ro.uow.edu.au/theses/119.
Full textAbstract:
Salmonella spp., in particular Salmonella Typhimurium is an important zoonotic pathogen both here in Australia and internationally. Over the past few decades the use of antimicrobials in human, agricultural and aquacultural settings has created significant selection pressures, giving rise to multiply antibiotic resistant bacteria, including Salmonella. The acquisition and dissemination of the genes responsible for antimicrobial resistance has been largely attributed to mobile genetic elements, including Class 1 integrons and the gene cassettes they contain. The initial aim of this study was to examine a collection of 136 multiply resistant Salmonella of different serovars from varying Australian sources (predominately animal and to a lesser extent human) for the presence of Class 1 integrons and to identify the gene cassettes present. Using PCR to amplify up specific regions within the Class 1 integron structure, 51.4% of the isolates examined were found to contain the Class 1 integron associated intI1 integrase. All of these, apart from 11 isolates, contained cassette arrays which were characterised using restriction enzyme analysis and DNA sequencing. The gene cassettes identified among the collection were almost solely responsible for resistance to trimethoprim and aminoglycosides. The dfrA5 gene cassette (responsible for resistance to trimethoprim) was the most prevalent cassette, particularly among the bovine isolates. Three new gene cassettes responsible for resistance to aminoglycosides, trimethoprim and lincosamides (aacCA5, dfrB6 and linG, respectively) were identified. SGI1 (Salmonella Genomic Island 1), a 43 kb chromosomal island known to contain a large multi-drug resistance integron, In104 was found to be present in 10 experimental isolates and associated with 4 new serovars, namely Kiambu, Dusseldorf, Cerro and Emek. The integron in the Salmonella Emek strain was found to have inserted via transposition at a unique site within the island backbone and this structure has been named SGI2. This unique insertion site suggests that SGI2 has evolved independently of SGI1.A second collection of multi-drug resistant almonella Paratyphi BdT+ isolates sourced from human infections in Melbourne and the corresponding home aquaria of infected patients were examined for clonality and the presence of SGI1. All S. Paratyphi BdT+ from infected individuals were indistinguishable from the isolates from their respective fish tanks, using IS200 profiling techniques and pulse field gel electrophoresis of XbaI digested chromosomal DNA. SGI1 (containing the aadA2 and blaP1 gene cassettes) was found to be present in all the S. Paratyphi BdT+ isolates examined. This is the first definitive molecular study showing that ornamental fish tanks are a reservoir for multiply resistant Salmonella aratyphi BdT+. Studies examining the molecular mechanisms involved in antimicrobial resistance, and the way in which mobile elements are incorporated and clustered into large multi-drug resistance regions such as SGI1, provide useful information needed for the ongoing surveillance of multiply resistant Salmonella and other bacterial pathogens involved in outbreaks domestically and internationally.
38
Patel, Nehal J. "Comparsion [sic] of antibiotic sensitivity profiles, molecular typing patterns, and attribution of Salmonella enterica serotype Newport in the U.S., 2003-2006." unrestricted, 2007. http://etd.gsu.edu/theses/available/etd-07262007-154647/.
Full textAbstract:
Thesis (M.P.H.)--Georgia State University, 2007.Title from file title page. Karen Gieseker, committee chair; Michael Eriksen, Peter Gerner-Smidt, Kelley Hise, committee members. Electronic text (105 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Nov. 28, 2007. Includes bibliographical references (p.101-105).
39
Chou, So-ha, and 周素霞. "Molecular epidemiology of carbapenem-resistant acinetobacter baumanniiin patients and their surrounding environment." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48333669.
Full textAbstract:
Background
There has been an increasing awareness of the role of the hospital environment as a reservoir of Acinetobacter baumannii. A. baumannii is an important nosocomial pathogen and is difficult to control due to the increasing cases of resistance to carbapenem.
Objectives
The objectives of this study areto examine carbapenem-resistant Acinetobacter baumannii (CRAB) positive patients according to their environmental sample to determine how frequently the environment surrounding the patient becomes contaminated and which environmental surfaces are most commonly contaminated.
Methodology
During June 2011 to December 2011, data regarding 30 hospitalized patients with at least one positive CRAB clinical sample were collected from hospital X in Kowloon of Hong Kong. For 30 case patients, one patient in the ICU ward had been isolated in a single room and the other 29 patients stayed in a multi-room. Fifteen surfaces in the patient cubicle and nine surfaces in health care worker stations were evaluated for the presence of CRAB. 29 control environmental samples were obtained from the surroundings of patients without CRAB in the same cubicle and one control environmental sample was obtained from the surroundings of patients without CRAB in the other room of ICU. Pulsed-field gel electrophoresis was performed on all environmental isolates and clinical samples.
Results
Of the 30casepatients, 26 patients (86.7%) were found to have CRAB contamination in their surrounding environment and 6negative control patients (20%) were found to have CRAB in their environmental samples. The percentage of positive CRAB cultures in the case environment, control and health care worker stations was 28.9% (117/405), 3.4% (14/406) and 1.9% (5/265)respectively. In the surrounding case patient area, pillows (60% 18/30) and bed sheets on which the patients sleep on (60% 18/30), bed sheets covering the patients (50% 15/30) and bedside table tops (40% 12/30) were the most commonly contaminated. For 26casepatientswere found to have CRAB contamination in their surrounding environment, 23 (88.5%) of these patients were found to have the clone of isolates in the case environment related to the patients.
Conclusion
For patients with CRAB, the surrounding environment is frequently contaminated.
Surfaces often touched by the patients are commonly contaminated. CRAB was also found on surfaces that were not closely related to the patient which are frequently touched by healthcare workers during patient care.published_or_final_version
Microbiology
Master
Master of Medical Sciences
40
Chan, Jane, and 陳曉婷. "Molecular epidemiology of fosfomycin-resistant Escherichia coli from humans and animals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/197077.
Full textAbstract:
The diminishing choice of effective antibiotics against resistant pathogens has forced clinicians to revive the use of old antibiotics. Hence, fosfomycin has been frequently suggested for alternative therapies given its track record of low resistance rates despite extensive use. However, there have been recent reports of plasmid-mediated fosfomycin resistance among animals and healthy humans in Asia. Accordingly, comparison of shared fosfomycin resistance mechanisms between animals and humans will shed light on the spread of resistance and guide future use of antimicrobials.
This study aimed to investigate plasmid-mediated fosfomycin resistance in E. coli isolates collected from patients and animals in Hong Kong. Non-duplicate E. coli isolates were cultured from 1711 urinary isolates and 167 blood clinical samples collected from multiple centres during 1996-2008 and from fecal samples of 210 cattle, 214 pigs, 460 chickens, 398 stray cats, 368 stray dogs and 456 wild rodents during 2008-2010.
A total of 2106 animal samples yielded 1693 E. coli isolates of which 831 were ESBL-producers. Fosfomycin-resistant isolates were more likely than fosfomycin-susceptible isolates to be ESBL-producers and multidrug resistant (≥3 antimicrobial classes). Of the 101 fosfomycin-resistant isolates, 97 (96.0%) were fosA3 positive and 94 (93.1%) were blaCTX-M positive. Of the 1878 clinical isolates, 18 were fosfomycin-resistant of which six were fosA3-positive and two were positive for another fosA variant (designated fosKP96). All but one fos-carrying clinical isolate was ESBL-producing. The majority of the fos-carrying E. coli strains belonged to diverse clones under two main clonal complexes CC58 accounting for 38 (36.2%) strains and CC10 for 32 (30.5%) strains.
PCR mapping showed that all fosA3-containing regions were followed by a downstream IS26. In all clinical isolates and 81 (83.5%) of animal isolates, an IS26 was also found upstream. In 14 (14.4%) of animal isolates, the fosA3 gene was preceded by an upstream blaCTX-M-14-containing transposon-like structure (ΔISEcp1-blaCTX-M-14-ΔIS903 or ISEcp1-IS10-blaCTX-M-14-ΔIS903). For the remaining two animal isolates, the upstream region could not be defined.
In a random subset of 18 animal isolates, fosA3 was carried on transferable plasmids with sizes of 50–200 kb and the following replicons: F2:A-:B- (n = 3), F16:A1:B- (n = 2), F24:A-B- (n = 1), IncHI2 (n = 3), IncN (n = 2), IncI1 (n = 1), B/O (n = 1) and untypeable (n = 5). Among six fosA3-carrying clinical isolates, the distributions were: F2:A-:B- (n = 2), IncN (n = 1), multi-replicon F-:A-:B1/IncN (n = 1) and untypeable (n = 2). Both fosKP96-carrying plasmids belonged to IncN. Restriction fragment length polymorphism analysis showed that the four F2:A-:B- plasmids carrying fosA3 and blaCTX-M-3 genes from a pig, dog and two patients shared an almost identical pattern. The complete plasmid sequences further demonstrated their homology.
This study demonstrated the emergence of fosA3-mediated fosfomycin resistance among E. coli isolates from multiple sources. Highly similar IncFII plasmids and IS26 transposon-like structures appear to be the main vehicles for dissemination. This study also highlighted occurrence of plasmids carrying fosKP96 that may have been overlooked by others as this variant could not be detected by established PCR markers.published_or_final_version
Microbiology
Master
Master of Philosophy
41
Chu, Pui-shan, and 朱佩珊. "Antimicrobial resistant escherichia coli and sequence type 131 in urinary tract infections." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206499.
Full textAbstract:
Background
A pandemic clone, Escherichia coli sequence type 131 (ST131), has been disseminated worldwide and represents an important cause of antimicrobial resistant infections. The spread of this resistant clone has become a great public health concern.
Objectives
The aims of this study were to investigate the prevalence of ST131 in Escherichia coli isolates from human urinary cultures in Hong Kong and study the antimicrobial phenotypes of ST131.
Methodology
This study included 340 E. coli clinical urinary isolates obtained from patients in four district hospitals between May 2013 and July 2013 in Hong Kong. Antimicrobial susceptibilities were assessed by disk diffusion method with reference to CLSI. The isolates were investigated by phylogroup-specific and ST131-specific PCR assays. ST131 strains were further assessed for subclone distribution, antimicrobial resistance and extended-spectrum β-lactamase (ESBL) type.
Results
A total of 18.5% (63/340) of the E. coli population was identified as ST131. ST131 isolates were significantly more likely than non-ST131 isolates to be ciprofloxacin resistant (69.8%, 44/63 versus 31.0%, 86/277; P <0.001), gentamicin resistant (38.1%, 24/63 versus 24.9%, 69/277; P=0.03) and ESBL producers (41.3%, 26/63 versus 18.8%, 52/277; P <0.001). Among the ST131 E. coli isolates, 68.3% (43/63) belonged to the H30 subclone. Most H30 isolates were ST131-O25b (97.7%, 42/43). Also, the ST131-H30 E. coli subclone was statistically associated with ciprofloxacin resistance compared with the non-H30 ST131 isolates (P <0.001). Additionally, strains which were co-resistant to ciprofloxacin, co-trimoxazole and gentamicin were overwhelmingly associated with the H30 subclone than non-H30 (23.3%, 10/43 versus 0%, 0/20; P=0.02).
Conclusion
This study showed that ST131 isolates were widespread among human E. coli urinary isolates in Hong Kong. The increase in antimicrobial resistance phenotypes are highlighted with ST131, especially the H30 subclone isolates. The dissemination of the ST131 resistant clonal group has aroused clinical attention and limited the choice of empirical treatment.published_or_final_version
Medical Sciences
Master
Master of Medical Sciences
42
Christofilogiannis, Panagiotis. "Use of antibiotics in Greek mariculture." Thesis, University of Stirling, 2002. http://hdl.handle.net/1893/3250.
Full textAbstract:
Bacteriological survey of the fish pathogens in Greek mariculture between 1994- 1997 was followed by analysis of prevalence in sea bass, sea bream, sharpsnout bream and common Dentex and discussion of the impact of various fish pathogens. In addition antibiotic resistance profiles and frequencies were studied using quantitative antibiogram and MIC analysis for the two most commonly used antibiotics Oxolinic acid and Oxytetracycline and clinically relevant MIC breakpoints were extrapolated for different fish species and main fish pathogens. The kinetics of the above antimicrobials were analysed in eight experiments where two fish species namely sea bass and sea bream as well as two water temperatures were employed. Muscle, liver, serum, skin samples were analysed by two HPLC methods and two bioassay methods were developed. The relative importance and significance of these findings was evaluated in the general context of pharmacokinetic studies in fish. Kinetic data were compared to clinical data and practical implications were evaluated. Issues like antibiotic resistance and its implications, the implications of residues and resistance in human health and the environment were analysed in order to put this study in context. Conclusions tackled important aspects of antimicrobial chemotherapy and future work was suggested.
43
Zaffarano, Jennifer I. "Minimum inhibitory concentration of two common food phenolic compounds and their effects on the microbial ecology of swine feces in vitro." Lexington, Ky. : [University of Kentucky Libraries], 2003. http://lib.uky.edu/ETD/ukyansc2003t00099/JZThesis.pdf.
Full textAbstract:
Thesis--University of Kentucky (M.S.), 2003.Title from document title page. Document formatted into pages; contains ix, 127 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 110-126).
44
Hunt, Kevan Owen. "An epidemiological study in the greater Durban area of gram negative bacilli resistant to aminoglycoside antibiotics." Thesis, Cape Technikon, 1998. http://hdl.handle.net/20.500.11838/2254.
Full textAbstract:
Thesis (MTech (Medical Technology))--Cape Technikon, 1998.This study was undertaken to investigate resistance to aminoglycoside antibiotics and the transfer of resistance in selected Gram negative bacilli in hospitals in the Greater Durban area in order to determine whether the development of resistance in this region was similar to that found in other countries and whether it was the same in the hospitals in the region. It was intended that the study might expose the existence of nosocomial pathogens of a particular strain or endemic plasmids responsible for aminoglycoside antibiotic resistance. Strains of Klebsiella, Enterobacter and Serratia species and Escherichia coli resistant to gentamicin, tobramycin, netilmicin or amikacin were obtained. Resistance of the isolates obtained to the above aminoglycoside antibiotics was confirmed using a disc diffusion technique. Resistance mechanisms were initially assigned on the basis of resistance to these four aminoglycoside antibiotics. In approximately 50% of the isolates, including donor isolates and their respective transconjugants, resistance mechanisms were confirmed or revised on the basis of a changed resistance profile to a range of 12 aminoglycoside antibiotics in conjunction with DNA/DNA hybridization tests. Bacterial conjugation studies were performed on selected isolates to investigate the transfer of aminoglycoside resistance from Klebsiella pneumoniae isolates to recipient Escherichia coli. Plasmid profiles of all isolates and Escherichia colitransconjugants were compared to establish similarities. Isolates in three of the four genera of bacteria and all isolates collectively, demonstrated the greatest incidence of resistance to tobramycin. Amikacin resistance was, in all groups of isolates, the least frequently encountered. Collectively, the most frequent mechanisms of resistance were the AAC(3)-V and AAC(6')-1 enzymes One large hospital showed a high frequency of the AAC(3)-V modifying enzyme while in other hospitals a wider range of enzyme resistance mechanisms were evident. Plasmid profiles were generally dissimilar within and between different genera and the different hospitals.
Mangosuthu Technikon Research Fund
45
Sibanda, Thulani. "Assessment of antibacterial potentials of Garcinia Kola seed extracts and their interactions with antibiotics." Thesis, University of Fort Hare, 2007. http://hdl.handle.net/10353/71.
Full textAbstract:
The antibacterial potency of the extracts of the seed of Garcinia kola (bitter kola) was investigated in this study against a panel of referenced, environmental and clinical bacterial strains. The killing rates of the active extract as well as their potential for combination antibacterial therapy with standard antibiotics were also elucidated using standard procedures. The aqueous and acetone extracts of the seed were screened for activity against 27 bacterial isolates. The aqueous extract exhibited activity mainly against Gram positive organisms with Minimum inhibitory concentration (MIC) values ranging from 5 mgml-1 – 20 mgml-1, while the acetone extract showed activity against both Gram negative and Gram positive organisms with MIC values ranging from 10 mgml-1 - 0.156 mgml-1. The acetone extract also showed rapid bactericidal activity against Staphylococcus aureus ATCC 6538 with a 3.097 Log10 reduction in counts within 4 hours at 0.3125 mgml-1 and a 1.582 Log10 reduction against Proteus vulgaris CSIR 0030 at 5 mgml-1 after 1 hour. In addition, the aqueous, methanol and acetone extracts of the seeds also exhibited activity against four clinical strains of Staphylococcus isolated from wound sepsis specimens. The MIC values for the aqueous extract were 10 mgml-1 for all the isolates while the acetone and methanol extracts had lower values ranging from 0.3125 - 0.625 mgml-1. The acetone extract was strongly bactericidal against Staphylococcus aureus OKOH3 resulting in a 2.70 Log10 reduction in counts at 1.25 mgml-1 within 4 hours of exposure and a complete elimination of the organism after 8 hours. The bactericidal vi activity of the same extract against Staphylococcus aureus OKOH1 was weak, achieving only a 2.92 Log10 reduction in counts at 1.25 mgml-1 (4× MIC) in 24 hours. In the test for interactions between the acetone extract of the seeds and antibiotics, synergistic interactions were observed largely against Gram positive organisms using the FIC indices, (indices of 0.52 - 0.875) with combinations against Gram negatives yielding largely antagonistic interactions (indices of 2.0 to 5.0). Synergy (≥ 1000 times or ≥ 3 Log10 potentiation of the bactericidal activity) against both Gram negative and Gram positive organisms was detected by time kill assays mainly involving the antibiotics tetracycline, chloramphenicol, amoxycillin and penicillin G. Combinations involving erythromycin and ciprofloxacin consistently gave antagonistic or indifferent interactions. We conclude that the acetone extract of Garcinia kola seeds possess strong bactericidal activities against both Gram positive and Gram negative organisms and can be therapeutically useful in the treatment of bacterial infections including the problematic staphylococcal wound infections. In addition, the acetone extract can be a potential source of broad spectrum resistance modifying compounds that can potentially improve the performance of antibiotics in the treatment of drug resistant infections.
46
Zhang, Yiliang, and 张毅良. "Regulation, activities, and physiological functions of the multidrug efflux pump mdtEF during the anaerobic adaptation of Escherichia coli." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B4775266X.
Full textAbstract:
Drug efflux represents an important protection mechanism against antibiotics
and environmental toxic compounds in bacteria. Efflux genes constitute from 6%
to 18% of all transporters in bacterial genomes, yet their regulation, natural
substrates, and physiological functions are poorly understood. Among the 20
chromosomally encoded efflux genes in Escherichia coli K-12, only the
AcrAB-TolC efflux system is constitutively expressed under the ordinary
laboratory growth of E. coli. To explore conditions and circumstances that trigger
the expression of additional efflux genes as well as their physiological functions, I
examined the expression of all 20 efflux genes under a physiologically relevant
circumstance for E. coli, which is anaerobic condition in this study. I found that
expression of an RND type efflux pump MdtEF is up-regulated more than 20 fold
when E. coli is cultured under anaerobic conditions. Mutagenesis studies revealed
that the anaerobically induced expression of mdtEF is subject to the regulation of
the anaerobic global transcription factor ArcA. Direct drug efflux and tolerance
assay showed that anaerobically grown E. coli cells display an increased efflux
activity and enhanced drug tolerance in an MdtEF dependent manner, confirming
the functional up-regulation of the efflux pump MdtEF in the anaerobic
physiology of E. coli.
Since the up-regulation of mdtEF by anaerobic growth occurs in the absence
of antibiotics and drugs, I speculate that MdtEF has physiological functions under
the anaerobic growth of E. coli. To explore this, I first compared the viability of
ΔmdtEF and WT MG1655 strains and found that ΔmdtEF caused a decreased cell
survival during prolonged anaerobic growth of E. coli. Interestingly, this defect
became more pronounced when cells grow in the presence of 10 mM nitrate, but
no defect was observed in ΔmdtEF strain when cells grow in the presence of 40
mM fumarate under the same anaerobic conditions, suggesting that MdtEF has
physiological roles relevant to the anaerobic respiration of nitrate. I further found
that E. coli cells harboring the deletion of mdtEF are susceptible to indole
nitrosative derivatives, a class of toxic by-products formed and accumulated
within E. coli when the bacterium respires nitrate under anaerobic conditions, and
deletion of the genes responsible for the biosynthesis of indole, tnaAB, restores
the growth defect of the ΔmdtEF strain during anaerobic respiration of nitrate.
Taken together, I conclude that the multidrug efflux pump MdtEF expels the
nitrosated indole derivatives out of E. coli cells under anaerobic conditions. Since
the production and accumulation of nitrosyl indole derivatives is ascribed to the
reactive nitrogen species elicited when E. coli consumes nitrate, I propose that the
up-regulated multidrug efflux pump MdtEF functions to protect E. coli from
nitrosative damage in its anaerobic ecological niches.published_or_final_version
Biological Sciences
Master
Master of Philosophy
47
Petersson, Ann Cathrine. "Species specific susceptibility testing for [beta]-lactam antibiotics with special reference to staphylococci /." Lund : Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/68945092.html.
Full text
48
Risley, Claire. "The population dynamics of plasmid-mediated antibiotic resistance in salmonella typhimurium in chickens." Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:a70bda98-533f-41d0-b9a0-630457b3f982.
Full textAbstract:
A model of growth and plasmid transfer between strains of Escherichia coli and Salmonella typhimurium was developed with reference to the literature. This was the organising principle for the collection of a complete set of in vitro life history parameters of one S. typhimurium and one E. coli strain. In the course of estimating these parameters two results of note were obtained. Fits of the Lotka-Volterra competition model were obtained for data on S. typhimuiurm growing in competition with E. coli. The first noteworthy discovery was the failure of this model to account for several characteristics of growth of these strains under competition. The growth rates of plasmid-bearing and plasmid-free strains were obtained. The second main result came from examination of the results of the growth rate data, which revealed that the cost to S. typhimuiurm 576 of bearing the resistance plasmid was low (4%). The model was also used to simulate the effect of antibiotic dose on the density of the donor, recipient and transconjugant populations over time. These simulations predicted that there would be a convex relationship between antibiotic dose and transconjugant density (i.e. that the density would first rise, then fall, with increasing dose). Following from this result, laboratory experiments and in vivo experiments in chickens were directed towards obtaining information on the relationship between these two variables. This convex relationship was not demonstrated within a single experiment, although some experimental environments produced an increase in transconjugant density with dose, and others, a decrease. Few transconjugants were formed in vivo. In order to investigate the low cost of resistance and low rate of in vivo transconjugant production, cost of resistance and plasmid transfer rate of this plasmid in several strain combinations of E. coli and S. typhimuiurm was evaluated.
49
Payne, Dorothy Broughton. "Stability of clones over two decades and the role of murM in penicillin resistance and evolution of streptococcus pneumoniae." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2009r/payne.pdf.
Full textAbstract:
Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.Additional advisors: Asim K. Bej, Susan K. Hollingshead, Daniel D. Jones, Stephen A. Watts. Description based on contents viewed June 23, 2009; title from PDF t.p. Includes bibliographical references.
50
Low, Chee Kin Andrew. "Characterisation and evaluation of novel potential target (tubulin) for antimalarial chemotherapy /." Access via Murdoch University Digital Theses Project, 2004. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20050930.125714.
Full text