Academic literature on the topic 'Bacteria Bacteria Drug resistance in microorganisms. Staphylococcus'

In order to further analyze the relationship between the coating mechanism of microorganisms and their drug resistance, a study of ocular bacterial drug resistance considering the coating mechanism of microorganisms was proposed. Firstly, the mechanism of drug resistance was analyzed, and on this basis, the experimental study was carried out. Staphylococcus aureus DH5 with RP4 was used as the control α( R) Objective to investigate the relationship between drug-resistant bacteria and coating mechanism in the cross genus conjugation system of Pseudomonas aeruginosa PAOi and donor bacteria. The conclusion is that: under the condition that the horizontal transfer of drug-resistant genes between transgeneric bacteria in biofilm is inhibited, the frequency of drug-resistant gene conjugation and transfer gradually decreases, and the inhibition of the formation of drug-resistant bacterial biofilm will directly lead to the decrease of bacterial drug resistance.

Antimicrobial agents are currently the mainstay of treatment for bacterial infections worldwide. However, due to the increased use of antimicrobials in both human and animal medicine, pathogens have now evolved to possess high levels of multi-drug resistance, leading to the persistence and spread of difficult-to-treat infections. Several current antibacterial agents active against Gram-positive bacteria will be rendered useless in the face of increasing resistance rates. There are several emerging antibiotics under development, some of which have been shown to be more effective with an improved safety profile than current treatment regimens against Gram-positive bacteria. We will extensively discuss these antibiotics under clinical development (phase I-III clinical trials) to combat Gram-positive bacteria, such as Staphylococcus aureus, Enterococcus faecium and Streptococcus pneumoniae. We will delve into the mechanism of actions, microbiological spectrum, and, where available, the pharmacokinetics, safety profile, and efficacy of these drugs, aiming to provide a comprehensive review to the involved stakeholders.

Introduction. Increased resistance of microorganisms to traditional antibiotics has created a practical need for isolating and synthesizing new antibiotics. We aimed to study the antibiotic activity and resistance of bacteriocins produced by lactic acid bacteria and other microorganisms. Study objects and methods. We studied the isolates of the following microorganism strains: Bacillus subtilis, Penicillium glabrum, Penicillium lagena, Pseudomonas koreenis, Penicillium ochrochloron, Leuconostoc lactis, Lactobacillus plantarum, Leuconostoc mesenteroides, Pediococcus acidilactici, Leuconostoc mesenteroides, Pediococcus pentosaceus, Lactobacillus casei, Lactobacillus fermentum, Bacteroides hypermegas, Bacteroides ruminicola, Pediococcus damnosus, Bacteroides paurosaccharolyticus, Halobacillus profundi, Geobacillus stearothermophilus, and Bacillus caldotenax. Pathogenic test strains included Escherichia coli, Salmonella enterica, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus mycoides, Alcaligenes faecalis, and Proteus vulgaris. The titer of microorganisms was determined by optical density measurements at 595 nm. Results and discussion. We found that eleven microorganisms out of twenty showed high antimicrobial activity against all test strains of pathogenic and opportunistic microorganisms. All the Bacteroides strains exhibited little antimicrobial activity against Gramnegative test strains, while Halobacillus profundi had an inhibitory effect on Gram-positive species only. The Penicillium strains also displayed a slight antimicrobial effect on pathogenic test strains. Conclusion. The antibiotic resistance of the studied lactic acid bacteria and other bacteriocin-producing microorganisms allows for their use in the production of pharmaceutical antibiotic drugs.

AbstractThe air in public facilities contains microorganisms which may cause a wide variety of clinical syndromes in humans. This is particularly important in primary healthcare units, where patients with reduced immunity and staff are directly exposed to microbial pathogens. Air samples were collected from dispensing areas (customer areas) of five pharmacies using MAS-100 air sampler. The concentration of particular groups of microorganisms was determined with the use of selective media. The taxonomic analysis of mannitol-positive bacteria was conducted using the BIOLOG® method, based on metabolic characteristics of analyzed strains. The isolated molds were identified based on their macroscopic and microscopic features according to available keys. The antimicrobial susceptibility of identified staphylococci was tested using the disk diffusion method in accordance with The European Committee on Antimicrobial Susceptibility Testing recommendations. The highest average concentrations of heterotrophic bacteria and staphylococci were recorded in two hospital pharmacies. The highest average concentrations of molds were recorded in the pharmacies located in shopping centers. Taxonomic analysis indicated that Cladosporium and Penicillium spp. predominated among the isolated molds while Staphylococcus haemolyticus and Staphylococcus aureus, among mannitol-positive bacteria. Antibiograms showed that the majority of Staphylococcus strains (68.2%) were resistant to erythromycin. There was a statistically significant correlation between the concentration of investigated bacteria and the season of the year as well as the size and location of the pharmacies. The results demonstrate that there is a range of factors affecting air quality in public spaces and emphasize the fact that pharmacies can be a source of potentially pathogenic, drug-resistant bacteria.

Antibiotics, both broad- and narrow spectrum, are widely used for treatment of specific infection by a consortium of microorganisms or by a single pathogen, respectively. Oral or intravenous, or even topical administration of different categories of antibiotics in various forms is a common practice round the globe. Yet for the recent years a major public health issue has been raised by the emergence of the drug-resistance microorganisms. A number of researches focused on the issue of the ineffectiveness of antibiotics as well as regarding the evolution of the drugresistance genes within the pathogenic microorganisms. Isolation of the drug-resistant microorganisms including the multi-drug resistant (MDR) and the extensively drug resistant (XDR) bacteria from a range of patients with microbiological infections has been seriously challenging the disease mitigation approaches. Besides, the dominance of the methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant Staphylococcus aureus (VRSA), etc. are quite frequent as evident from different case studies. Current review focused on the origin and evolution of such drug-resistance incidences, and the promising remedies over the problems of drug-resistance. Bangladesh J Microbiol, Volume 36 Number 2 December 2019, pp 111-114

Present study attempted to emphasize on the drug-resistance attribute of the previously isolated microorganisms within the commonly available flowers including Hibiscus rosa-sinensis, Ixora coccinea, Ipomoea digitata, Allamanda cathartica, Nymphaea nouchali, Vinca rosea, Rosa kordesii, Gladiolus hybrid, Acmella oleracea, Nyctanthes arbor-tristis and Pseudomussaenda flava, randomly collected from different areas in Dhaka city, Bangladesh. Conventional agar well diffusion method was applied to examine the antibiogram of the isolates (Escherichia coli, Klebsiella spp., Pseudomonas spp., and Staphylococcus spp.) against different drugs. Subsequently the anti-bacterial traits of 6 flowers such as Rosa kordesii, Gladiolus hybrid, Acmella oleracea, Nymphaea nouchali (Water lily), Hibiscus rosa- sinensis (Jaba), Ixora coccinea (Rangan) were demonstrated through broth micro-dilution methods. Pseudomonas spp. showed sensitivity against almost 42% tested drugs. Conversely, Staphylococcus spp. (83%) and Klebsiella spp. (75%) revealed resistance against highest number of drugs. Among all the pathogens, E coli showed the highest sensitivity (50%) against all the tested antibiotics. All the isolated bacteria were found to be multi-drug resistant against commonly used antibiotics. Finally six (6) samples unveiled anti-bacterial features against 8 laboratory strains with their MIC concentrations up to 0.2 mg/mL.Stamford Journal of Microbiology, Vol.5(1) 2015: 5-8

Background: Human skin is colonized by various species of microorganisms, which makes them difficult to eliminate even with the use of antimicrobial drugs. Real efficacy of the antimicrobial product combined with incorrect administration of antibiotics, in addition to potential environmental contamination, are critical points for the establishment of postoperative infection or absence of it. The main objective of the present study was to evaluate the efficacy of surgical antisepsis using a 2% chlorhexidine brush during a surgery, detect operating room environmental contamination, and verify the existence of bacterial resistance to the antibiotics most commonly used in Veterinary Medicine.Materials, Methods & Results: In ten cases of the surgical routine, samples were collected concurrently at specific time points throughout 2 h of surgical procedure. To evaluate the efficacy of 2% chlorhexidine brush on hand scrubbing of a mock surgeon, swabs were used to sample the surface of the hands before and after gowning and gloving. Samples or their dilutions were inoculated onto blood agar and MacConkey agar plates. Contamination of the operating room was evaluated using BHI agar plates distributed through the room. After the incubation period, counts and biochemical tests were performed, and an antimicrobial disc susceptibility test was performed using antibiotics most commonly used in Veterinary Medicine.Discussion: Even though the surgical unit of the Veterinary Hospital “Governador Laudo Natel” is constantly sanitized, it is not free from microbial contamination. In the present study, there was no bacterial growth on MacConkey agar, which suggests absence of fecal contamination. Blood agar is a culture medium that provides optimal growth conditions to most pathogenic bacteria, which explains the higher microbial growth observed in this medium. Gram-positive cocci grew on blood agar forming grape bunch- and chain-like patterns, which indicates the possible presence of Staphylococcus sp. and Enterococcus sp. The results obtained to evaluate environmental contamination by means of BHI agar revealed growth of diverse microorganisms, with presence of Gram-positive cocci and Gram-negative rods. The biochemical tests indicated presence of microorganisms from various genera. About the evaluation of bacterial resistance to the antibiotics it was possible to observe high bacterial resistance to metronidazole, followed by ampicillin. Metronidazole has bactericidal activity against most of the anaerobic and facultative anaerobic bacteria, since the bacteria found were aerobic. As for ampicillin, it is considered a broad spectrum antibiotic, which indicates that the bacteria found can be resistant to this antibiotic. Clindamycin also resulted in bacterial high resistance, which shows that this drug was not effective against the Grampositive bacteria found in the samples studied. Enrofloxacin yielded high bacterial resistance indicating that wide use of this drug due to its intrinsic efficacy and safety might have contributed to the appearance of resistance. Results showed bacterial resistance to cephalexin, possibly indicating a lower efficacy in treatment against bacterial diseases, since a lot of the samples were Gram-positive. Bacterial resistance to ceftiofur was lower when compared to cephalexin; this can be related to the shorter time this drug has been in the market. The results revealed bacterial growth in the surgical environment, and verified the efficacy of 2% chlorhexidine for hand scrubbing. Spontaneous mutation and gene recombination contributes to the emergence of resistance is the indiscriminate use of antibiotics for the treatment of animals, which can contribute to bacterial resistance.

Control of microbiological safety of animal feed is regulated by a law. The regulation is based on methodological standards for estimation of feed quality. Those methods are permanently amended and strive for continuous improvement of microbiological safety of feed. The question remains whether the presence or absence of some bacterial species is sufficient for proper assessment of feed safety. The answer to this question can be found not only in the examination of the number of bacteria in animal feed, but also in qualitative analysis of the isolated microorganisms. The sensitivity of bacteria from animal feed to antimicrobials is one of the qualitative characteristics of microorganisms that can affect food safety even if the feed meets the standards and is within the maximum permitted level. The subject of our work was to determine the presence of bacteria in animal feed with a purpose to examine if they possess lower sensibility to antibiotics. For testing antibiotic sensitivity the isolates from routine microbiological feed control were used. The animal feed was analysed by the standard methods for the isolation and identification of bacteria and determination of susceptibility was done using disc diffusion method according to CLSI. The following bacteria were detected: Escherichia coli, Enterobacter sp., Staphylococcus sp., Micrococcus sp., Bacillus cereus, Bacillus sp. The results showed that some isolates have reduced susceptibility to certain antimicrobial drugs (The resistance is different for different antibiotics and microorganism - from 8,33% to 100%). This finding gives a reason for further examination of certain characteristics of the bacteria found in animal feed and to detect their possible influence on ecology.

Introduction: Healthcare waste (HCW) might potentially harbor infective viable microorganisms in sanitary landfills. We investigated the antimicrobial susceptibility patterns and the occurrence of the mecA gene in coagulase-negative Staphylococcus strains (CoNS) recovered from the leachate of the HCW in an untreated sanitary landfill. Methodology: Bacterial identification was performed by physiological and molecular approaches, and minimum inhibitory concentrations (MICs) of antimicrobial drugs were determined by the agar dilution method according to CLSI guidelines. All oxacillin-resistant bacteria were screened for the mecA gene. Results: Out of 73 CoNS, seven different species were identified by 16S rDNA sequencing: Staphylococcus felis (64.4%; n = 47), Staphylococcus sciuri (26.0%; n = 19), Staphylococcus epidermidis (2.7%; n = 2), Staphylococcus warneri (2.7%; n = 2), Staphylococcus lentus (1.4%; n = 1), Staphylococcus saprophyticus (1.4%; n = 1), and Staphylococcus haemolyticus (1.4%; n = 1). Penicillin was the least effective antimicrobial (60.3% of resistance; n = 44) followed by erythromycin (39.8%; n = 29), azithromycin (28.8%; n = 21), and oxacillin (16.5%; n = 12). The most effective drug was vancomycin, for which no resistance was observed, followed by gentamicin and levofloxacin, for which only intermediate resistance was observed (22%, n = 16 and 1.4%, n = 1, respectively). Among the oxacillin-resistant strains, the mecA gene was detected in two isolates. Conclusions: Considering the high antimicrobial resistance observed, our results raise concerns about the survival of putative bacterial pathogens carrying important resistance markers in HCW and their environmental spread through untreated residues discharged in sanitary landfills.

Cockroaches are among the most common pests in public dwellings and health facilities. Owing to their close association with man and all his surroundings they are consideredas potential carrier and transmitter of human diseases. In hospital, cockroaches are the possible vector of nosocomial infection, specially for the transmission of drug resistant bacteria. The aim of the present study was to identify the major cockroach species, to isolate common foodborne pathogens from cockroach and to determine the antibiotic susceptibility pattern of isolated bacteria. This casecontrol study was conducted on cockroaches captured from hospital, restaurants and houses in Dhaka city, from a period of July to December 2014. A total of 450 cockroaches were collected. Among these 300 cockroaches (150 from hospital and 150 from restaurants) were considered as case and 150 cockroaches from houses were enrolled as control group. All (100%) cockroaches were identified as Blattellagermanica. Examination of external surface and gut homogenates showed that all (100%) cockroaches carried bacteria, while carriage rate of fungi and parasites were 28.2% and 3.7% respectively. Of 1901 isolated bacteria, Escherichia coli (15.3%), Pseudomonas aeruginosa (14.4%) and Salmonella spp.(12.9%) were the predominant bacteria. Other bacteria of medical relevance included,Shigella spp. (6.4%), Klebsiella spp. (8.8%), Proteus spp. (9.6%) and Staphylococcus aureus (4.3%). Antibiotic resistance pattern showed high resistance rate (62.4%) of bacterial isolates to different antibiotics. Additionally, 1051(55.3%) of the isolates were multi drug resistant (MDR) strains, which were resistant to 5-14 antibiotics. The findings of this study revealed that, cockroaches are potential source of pathogenic microorganisms including multi drug resistant bacterial strains, which could be a major threat to public health. Hence, effective preventive and control measures are required to minimize cockroach related infections.Bangladesh Med Res Counc Bull 2018; 44(1):30-38

Dissertation (Ph.D.)--University of Toledo, 2009.
Typescript. "Submitted in partial fulfillment of the requirements for The Doctor of Philosophy in Biology (Ecology-Track)." Bibliography: leaves 108-126.

A study to assess the potentials of some commensal bacteria that belong to Staphylococcus, Acinetobacter and Stenotrophomonas genera as reservoirs of antibiotic resistance determinants in the environment of Nkonkobe Municipality of the Eastern Cape Province, South Africa, was carried out using standard microbiological and molecular techniques. A total of 120 Staphylococcus isolates which consisted of Staphylococcus haemolyticus (30%), Staphylococcus aureus (23.3%) from pig; Staphylococcus capitis (15%) from goat; Staphylococcus heamolyticus (5%) and Staphylococcus xylosus (15%) from cattle and other Staphylococci (11%) from dead chicken and pigs were isolated. About 23.3% of these isolates were coagulase positive and 76.7% were coagulase negative. This difference in prevalence along coagulase production divide was statistically significant (p < 0.05). Eighty-six Acinetobacter species (Acinetobacter baumannii/calcoaceticus and Acinetobacter haemolyticus) were also isolated from Alice and Fort Beaufort towns samples, while 125 Stenotrophomonas maltophilia isolates were from grass root rhizosphere (96%) and soil butternut root rhizosphere (4%). Between 75-100% of the Staphylococccus species were resistant to Penicillin G, tetracycline, sulphamethaxole and nalidixic acid; about 38 % were methicillin resistant, consisting of 12.6% methicillin resistant Staphylococcus aureus (MRSA) from pig and a total of 12% vancomycin resistant were observed. Also, 12% of the isolates were erythromycin resistant while 40.2 % were resistant to the third generation cephalosporin, ceftazidime. The antibiotic resistance genes vanA, VanB, eryA, eryB, eryC were not detected in all the phenotypically resistant Staphylococccus species, but mec A gene and mph genes were detected. In the Acinetobacter species, a wide range of 30-100% resistance to penicillin G, ceftriazone, nitrofurantoin, erythromycin, and augmentin was observed. Polymerase chain reaction (PCR) revealed the presence of Tet(B) and Tet(39) genes in these species, while Tet (A), Tet(M) and Tet(H) were absent. Also, 9.3% of the Acinetobacter species showed phenotypic production of extended spectrum beta lactamases (ESBLs) while 3.5% were positive for the presence of blaCTX-M-1 genes. The Stenotrophomonas maltophilia isolates showed varying resistance to meropenem (8.9%), cefuroxime (95.6 %), ampicillin-sulbactam (53.9%), ceftazidime (10.7%), cefepime (29.3 %), minocycline (2.2%), kanamycin (56.9%), ofloxacin (2.9%), levofloxacin (1.3%), moxifloxacin (2.8%), ciprofloxacin (24.3%), gatifloxacin (1.3%), polymyxin B (2.9 %), cotrimoxazole (26.1%), trimethoprim (98.6%), aztreonam(58%) and Polymyxin B (2.9 %). The isolates exhibited significant susceptibility to the fluoroquinolones (74.3-94.7 %), polymycin (97.1%) and meropenem (88.1%). Only sul3 genes were the only sulphonamide resistance gene detected among the trimethoprim-sulphamethoxazole resistant isolates. The observed multiple antibiotic resistance indeces (MARI) of >2 for Staphylococcus species, Acinetobacter species and Stenotrophomonas maltophilia suggest that they have arisen from high-risk sources where antibiotics are in constant arbitrary use resulting in high selective pressure. The presence of tetracycline resistance genes in Acinetobacter species justifies the observed phenotypic resistance to oxytetracycline and intermediate resistance to minocycline. High phenotypic resistance and the presence of some resistance genes in Staphylococcus species is a possible threat to public health and suggests animals to be important reservoirs of antibiotic resistance determinants in the environment. Indiscriminate use of antibiotics induces this kind of antibiotic resistance and should be discouraged. Personal hygiene is encouraged as it reduces the load of Acinetobacter species contacted from the environment that may be difficult to control. Commensal Stenotrophomonas maltophilia are as important as their clinical counterparts due to their roles in opportunistic infection, antibiotic resistance and their associated genes, especially sul gene. Personal hygiene is hereby advocated especially when in contact with soil, plants and plants’ rhizospheric soil

Thesis (MTech (Biomedical Sciences))--Cape Peninsula University of Technology, 2015.
Wastewater treatment plants (WWTPs) are designed to remove/decrease conventional pollution parameters from the wastewater influent, so that the final effluent (run off) does not compromise the receiving surface water source. However, as hospital and clinical effluent may form part of the initial influent at a WWTP, bacteria may be exposed to various antibiotics or pharmaceuticals throughout the various stages of primary, secondary and tertiary processes utilised to remove or reduce the level of pollutants. Numerous studies have then indicated that WWTPs have become potential reservoirs for antibiotic resistant bacteria (ARB) and due to ineffective treatment practices, antibiotics are being released into the environment. Consequently, research has shown that relatively low concentrations of these compounds still promotes the development of bacterial resistance, which potentiates the rapid spread of ARB in the environment. The primary aim of this study was thus to identify and trace the antibiotic resistant strains of Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) throughout the Stellenbosch WWTP. This was done in order to determine the persistance of the ARB organisms at the various stages of treatment and to ascertain which identification and antibiotic resistance detection methods are ideal for the routine application and detection of these organisms.
National Research Foundation

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.

Resistance to antimicrobials is a well-known phenomenon leading to difficulties in the treatment of infectious diseases. The genetic determinants of such resistance are in general well understood: plasmids, transposons, insertion sequences and integrons are the most frequently related genetic elements. The word epigenetics refers to changes in the phenotype or in the gene expression caused by mechanisms other than underlying DNA sequence. In some cases these changes can remain for generations. Serratia marcescens is an enterobacterium characterized by its natural (intrinsic) resistance to most antibiotics. It is also a relevant opportunistic pathogen which has been involved in several pathologies such as urinary tract infections, prostheses infections, cellulitis, bacteremia and others. P. aeruginosa is a Gram-negative bacterium considered one of the major nosocomial pathogens worldwide. It causes several infections such as wound and burn infections as well as respiratory tract infections mostly affecting cystic fibrosis patients. An increasing prevalence of infections caused by multidrug-resistant (MDR) isolates has been reported in many countries and is actually a cause of concern. Both, P. aeruginosa and S. marcescens are relevant nosocomial pathogens. Some of the classic antimicrobials used to treat these pathogens are out-of-date and several of the new drugs available have already become targets for bacterial mechanism of resistance. Environmental conditions exert high pressure not only in the selection of genes encoding resistance to antibiotics or integron fixation in bacterial genomes or plasmids and other mobile elements transmission, but also in the expression of these potentialities that leads to resistance. Thus the role of epigenetics remains to be investigated. In addition it is well known that bacteria causing infections are naturally forming part of biofilms instead the planktonic way of life normally assumed to be in laboratory conditions. The aim of this thesis was the study of unconventional mechanisms of antimicrobial resistance contributing to MDR phenotypes in both S.marcescens and P. aeruginosa. Also the exploration of changes in antimicrobial susceptibilities of Serratia marcescens in the last 50 years by comparing isolates collected between 1945 and 1950, and current isolates. ¬The main conclusions obtained from this study are: 1. The resistome of Serratia marcescens did not change significantly during the antibiotic era. 2. Antibiotic withdrawing tends to restore original susceptible phenotypes, irrespective to the molecular mechanism involved in resistance. 3. None of Serratia strains studied presented integrons, any extended spectrum ß-lactamases. 4. Phenotypically determination of susceptibilities of old strains inactive during the last 60 years have confirmed results obtained by metagenomics i.e. the genes of resistance already existed before antibiotics discovery and use. 5. Multiresistant Pseudomonas aeruginosa harbored class 1 integrons containing a cassette encoding aminoglycoside adenylyltransferase (aadB). 6. Multiresistant Pseudomonas aeruginosa overexpressed MexAB-OprM and MexXY efflux machinery. 7. CCCP use should be avoided in experiments performed with P. aeruginosa and probably in other aerobic bacteria. 8. Meropenem induces the formation of aberrant long rods which can survive, accumulate less antibiotic than normal bacteria, and can revert to normal forma when antibiotic pressure disappears. 9. Colistin, the last therapeutic option to fight against Pseudomonas infections in cystic fibrosis patients, is normally active although cases of resistance have arisen recently. 10. Resistance to colistin seems to be mediated by lipopolysaccharide singular properties. 11. Colistin induces injuries in lipid bilayers, which can be studied by means of planar black lipid bilayer techniques. Preliminary results showed the ability of colistin to induce transient channels in the bilayers, with some dependence to voltage. 12. Recovery of susceptibility to imipenem is slower than acquision of resistance, since the selective advantage conferred by imipenem resistance in the presence of the antimicrobial is strong whereas OprD expression is likely evolutionarily advantageous only under certain and unknown environmental conditions.
Es van explorar els mecanismes no convencionals de resistència als agents antimicrobians que contribueixen a l’aparició de fenotips multiresistents en els bacteris Gram-negatius Serratia marcescens i Pseudomonas aeruginosa. Es van examinar també els canvis en la susceptibilitat als agents antimicrobians en S. marcescens durant els darrers 50 anys, comparant soques aïllades entre els anys 1945-1950 y soques actuals. ¬Les principals conclusions obtingudes d’aquest estudi són les següents: 1. El resistoma de Serratia marcescens no ha canviat significativament des de l’era pre-antibiòtica fins l’actualitat. 2. La retirada dels antibiòtics tendeix a recuperar els fenotips de susceptibilitat originals, independentment del mecanisme molecular implicat en la resistència. 3. Cap de las soques de Serratia estudiades va presentar integrons ni tampoc ß-lactamases d’espectre estès. 4. La determinació fenotípica de les susceptibilitats de las soques “antigues” de Serratia inactives durant 60 anys ha confirmat els resultats obtinguts mitjançant metagenòmica, és a dir, els gens de resistència als antibiòtics ja existien amb anterioritat al descobriment i ús dels antibiòtics. 5. En les soques clíniques de P. aeruginosa multiresistents es va detectar un integró de classe 1 que contenia el cassette gènic aadB, que codifica l’enzim aminoglicòsid 2’-O- adeniltransferasa, que confereix resistència a gentamicina, tobramicina i kanamicina. 6. Les soques multiresistents de P. aeruginosa van sobreexpressar els sistemes de reflux MexAB-OprM i MexXY-OprM. 7. L’ús de l’inhibidor de bombes de reflux CCCP s’hauria d’evitar als experiments realitzats amb P. aeruginosa i probablement amb altres bacteris de metabolisme aeròbic. 8. El meropenem indueix la formació de llargs bacils aberrants capaços de sobreviure en presència de l’antibiòtic. Aquests bacils acumulen menys antibiòtic que els bacteris normals, i poden revertir a la forma normal quan s’elimina la pressió selectiva. 9. La colistina, la última alternativa terapèutica per lluitar contra P. aeruginosa en pacients amb fibrosis quística, és normalment efectiva, encara que recentment han sorgit casos de resistència a aquest agent antimicrobià. 10. La resistència a colistina sembla estar causada per propietats singulars del lipopolisacàrid. 11. La colistina produeix danys en les membranes lipídiques que poden ser estudiats mitjançant tècniques de Black lipid bilayer. Estudis preliminars van mostrar la capacitat de la colistina para induir canals transitoris en les bicapes lipídiques, amb certa dependència de voltatge. 12. La recuperació de la susceptibilitat a l’imipenem en P. aeruginosa és més lenta que l’adquisició de resistència, donat que l’avantatge selectiva conferida per la resistència a l’imipenem en presència de l’agent antimicrobià és forta, mentre que l’expressió d’ OprD és probablement avantatjosa solament sota certes i desconegudes condicions ambientals.
Se exploraron los mecanismos no convencionales de resistencia a agentes antimicrobianos que contribuyen a la aparición de fenotipos multiresistentes en las bacterias Gram-negativas Serratia marcescens y Pseudomonas aeruginosa. Se examinaron también los cambios en la susceptibilidad a los agentes antimicrobianos en S. marcescens en los últimos 50 años, comparando cepas aisladas entre los años 1945-1950 y cepas actuales. ¬Las principales conclusiones obtenidas de este estudio son las siguientes: 1. El resistoma de Serratia marcescens no ha cambiado significativamente desde la era pre-antibiótica hasta la actualidad. 2. La retirada de los antibióticos tiende a recuperar los fenotipos de susceptibilidad originales, independientemente del mecanismo molecular implicado en la resistencia. 3. Ninguna de las cepas de Serratia estudiadas presentó integrones ni tampoco ß-lactamasas de espectro extendido. 4. La determinación fenotípica de las susceptibilidades de las cepas “antiguas” de Serratia inactivas durante 60 años ha confirmado los resultados obtenidos mediante metagenómica, es decir, los genes de resistencia a los antibióticos ya existían con anterioridad al descubrimiento y uso de los antibióticos. 5. En las cepas clínicas de P. aeruginosa multiresistentes se detectó un integrón de clase 1 que contenía el cassette génico aadB, que codifica la enzima aminoglicósido 2’-O- adeniltransferasa, que confiere resistencia a gentamicina, tobramicina y kanamicina. 6. Las cepas multiresistentes de P. aeruginosa sobreexpresaron los sistemas de reflujo MexAB-OprM y MexXY-OprM. 7. El uso del inhibidor de bombas de reflujo CCCP se debería evitar en los experimentos realizados con P. aeruginosa y probablemente con otras bacterias de metabolismo aeróbico. 8. El meropenem induce la formación de largos bacilos aberrantes capaces de sobrevivir en presencia del antibiótico. Estos bacilos acumulan menos antibiótico que las bacterias normales, y pueden revertir a la forma normal cuando se elimina la presión selectiva. 9. La colistina, la última alternativa terapéutica para luchar contra P. aeruginosa en pacientes con fibrosis quística, es normalmente efectiva, aunque recientemente han surgido casos de resistencia a este agente antimicrobiano. 10. La resistencia a colistina parece estar mediada por propiedades singulares del lipopolisacárido. 11. La colistina produce daños en las membranas lipídicas que pueden ser estudiados mediante técnicas de Black lipid bilayer. Estudios preliminares mostraron la capacidad de la colistina para inducir canales transitorios en las bicapas lipídicas, con cierta dependencia de voltaje. 12. La recuperación de la susceptibilidad al imipenem en P. aeruginosa es más lenta que la adquisición de resistencia, dado que la ventaja selectiva conferida por la resistencia al imipenem en presencia del agente antimicrobiano es fuerte, mientras que la expresión de OprD es probablemente ventajosa sólo bajo ciertas y desconocidas condiciones ambientales.

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

Garcinia kola is one of the plants used in folklore remedies for the treatment of microbial infections. Bacterial resistance to commonly used antibiotics has necessitated the search for newer and alternative compounds for the treatment of drug resistant microbial infections. This study focuses on the bioactivity of G. kola seeds on Streptococcus pyogenes (ATCC 49399), Staphylococcus aureus (NCTC 6571), Plesiomonas Shigelloides (ATCC 51903) and Salmonella typhimurium (ATCC 13311), organisms which can cause illnesses from mild to severe with potentially fatal outcomes. The crude ethyl acetate, ethanol, methanol, acetone and aqueous extracts were screened by agar-well diffusion method and the activities of the extract were further determined by Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays. The inhibition zones ranged from 0 - 24 mm, while MIC and MBC of the extract ranged between 0.04 - 1.25 mg/mL and 0.081 - 2.5 mg/mL respectively. Chloroform/ Ethyl Acetate/ Formic acid (CEF) solvent system separated more active compounds followed by Ethyl Acetate/ Methanol/ Water (EMW) and Benzene/ Ethanol/ Ammonium Hydroxide (BEA). The extracts were fractionated by Thin Layer Chromatography (TLC). Bioautography was used to assess the activity of the possible classes of compounds present in the more active extracts. Column chromatography was used to purify the active compounds from the mixture while Gas Chromatography-Mass Spectrometry (GC-MS) was used to identify the phyto components of the fractions. The MIC of the fractions ranged between 0.0006 - 2.5 mg/mL. CEF 3 (F3), CEF 11 (F11) and CEF 12 (F12) revealed the presence of high levels fatty acids Linoleic acid, 1, 2-Benzenedicarboxylic acid and 2, 3-Dihydro-3, 5-dihydroxy-6-methyl, respectively. The results obtained from this study justify the use of this plant in traditional medicine and provide leads which could be further exploited for the development of new and potent antimicrobials.

Staphylococcus aureus is a Gram-Positive bacteria that are responsible to cause skin infections and also shows toxic shock syndrome. Several antibiotics were given against the S. aureus infections but eventually, the prevalence of multidrug resistance of Staphylococcus aureus started emerging. Since then Methicillin-resistant Staphylococcus aureus strains (MRSA)were very common which causes nosocomial infections. Microorganisms for the need of the survival undergoes mutational changes either in their chromosomal DNA/RNA which confers the resistance. One of the famous examples is the resistance against methicillin in Staphylococcus aureus. The evolution of S. aureus is successful in developing multiple resistant strains. Plasmids are capable of carrying the resistant genes and also several toxic genes. In a recent study, it has been observed that drug resistance genes are located in the R plasmids and they are also responsible in conferring multi drug resistance and induce less utilization of multiple antimicrobial therapy. MRSA was not only resistant to methicillin, studies proved MRSA strains were resistant to macrolides, tetracyclines, chloramphenicol. Resistance to vancomycin was very evidently observed, and its transfer among the population and rising of resistant strains was becoming a major threat globally. The resistance of all these antimicrobial agents against the pathogenic microorganisms are taking a rise in some patients due to prolong use of the antimicrobial agents by these patients. The multi drug resistance has enhanced the mortality and morbidity rate which referred to the infecting agents as the “Super Bugs”. Survival of the microorganisms has increased due to the gradual development of extensive resistance against varied antimicrobial drugs. Possible treatments with combinations are found to be the only hope for infections against S. aureus. Few drugs are in development such as Dalbavancin, Oritavancin, Tigecycline. These are the possible treatments upon which the work is going on to reduce the resistance against the invasive MRSA. This chapter highlights the profiles of Staphylococcus aureus and the resistance patterns along with transmission and the role of the plasmid in transmitting the resistance.

Staphylococcus aureus is the most ubiquitous microorganism in both environment as well as animals and exists as commensal and pathogenic bacterium. In past few years it has been emerged as a superbug causing serious burden on healthcare system. This bacterium has been found to be the most resistant one toward most of the antibiotics due to its rapid structural and genetic modifications. This chapter will shed light on various types of molecular mechanisms responsible for resistance of Staphylococcus aureus showcasing how it has been emerged as a superbug. Moreover, the recent approaches which include exploring of different drug targets keeping in view the structural and functional behavior of the Staphylococcus aureus has also been discussed.

Staphylococcus aureus is a colonizing microorganism of the nasal region of both humans and animals and represents an important opportunistic pathogen. The acquisition of the mecA and mecC genes by S. aureus led to the emergence of methicillin resistance (MRSA), becoming a public health problem in both human and animal areas. In addition to resistance to β-lactam antibiotics, MRSA strains have multidrug resistance to antimicrobials, significantly limiting therapeutic options, making it crucial to have effective alternatives for treating staphylococcal infections. In this context, the use of lytic bacteriophages, which are viruses that infect and lyse bacteria, as well as the use of their by-products, such as endolysins, has shown potential in the control of S. aureus, including MRSA. Due to the specificity of bacteriophages to infect particular prokaryotic hosts, these viruses represent an antibacterial resource for the control of public health relevant microorganisms, especially antibiotic-resistant bacteria.