Conjugative multiple-antibiotic resistance plasmids in Escherichia coli isolated from environmental waters contaminated by human faecal wastes. - Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
335601.0000Conjugative multiple-antibiotic resistance plasmids in Escherichia coli isolated from environmental waters contaminated by human faecal wastes. AIMS: To better understand the involvement of faecal contamination in the dissemination of antibiotic resistance genes, we investigated the genetic supports of resistances in nine multi-resistant Escherichia coli strains originating from human faecal contamination, and isolated from three different aquatic environments used for producing drinking water. METHODS AND RESULTS: Seven strains harboured at least one large plasmid that we have characterized (size, antibiotic resistance patterns, incompatibility group, capacity of autotransfer, presence of integron). Most of these plasmids were conjugative and carried numerous resistances. One of the plasmids studied, belonging to the IncP incompatibility group, was able to transfer by conjugation to Pseudomonas fluorescens and Aeromonas sp. Only two of the plasmids we studied carried class 1 and/or 2 integron(s). CONCLUSIONS: Conjugative plasmids isolated from multi-resistant E. coli strains explained most of the resistances of their host strains and probably contribute to the spread of antibiotic resistance genes coming from human faecal contamination. SIGNIFICANCE AND IMPACT OF THE STUDY: These results highlight the key role played by plasmids in the multi-resistance phenotype of faecal bacteria and the diversity of these genetic structures. Contaminated water, especially accidentally contaminated drinking water, could be a path back to humans for these plasmids.201525387599
339410.9999Antibiotic resistance patterns of Pseudomonas spp. isolated from faecal wastes in the environment and contaminated surface water. The Pseudomonas genus, which includes environmental and pathogenic species, is known to present antibiotic resistances, and can receive resistance genes from multi-resistant enteric bacteria released into the environment via faecal rejects. This study was aimed to investigate the resistome of Pseudomonas populations that have been in contact with these faecal bacteria. Thus, faecal discharges originating from human or cattle were sampled (from 12 points and two sampling campaigns) and 41 Pseudomonas species identified (316 isolates studied). The resistance phenotype to 25 antibiotics was determined in all isolates, and we propose a specific antibiotic resistance pattern for 14 species (from 2 to 9 resistances). None showed resistance to aminoglycosides, tetracycline, or polymyxins. Four species carried a very low number of resistances, with none to β-lactams. Interestingly, we observed the absence of the transcriptional activator soxR gene in these four species. No plasmid transfer was highlighted by conjugation assays, and a few class 1 but no class 2 integrons were detected in strains that may have received resistance genes from Enterobacteria. These results imply that the contribution of the Pseudomonas genus to the resistome of an ecosystem first depends on the structure of the Pseudomonas populations, as they may have very different resistance profiles.202031930390
340820.9999The role of aquatic ecosystems as reservoirs of antibiotic resistant bacteria and antibiotic resistance genes. The widespread and indiscriminate use of antibiotics has led to the development of antibiotic resistance in pathogenic, as well as commensal, microorganisms. Resistance genes may be horizontally or vertically transferred between bacterial communities in the environment. The recipient bacterial communities may then act as a reservoir of these resistance genes. In this study, we report the incidence of antibiotic resistance in enteric bacteria isolated from the Mhlathuze River and the distribution of genetic elements that may be responsible for the observed antibiotic resistance. The resistance of the enteric bacteria isolated over a period of one year showed that resistance to the older classes of antibiotics was high (94.7% resistance to one antibiotic and 80.8% resistance to two antibiotics). Furthermore, antibiotic resistance data of the environmental isolates showed a strong correlation (r = 0.97) with data obtained from diarrhoea patients. PCR based methods demonstrated that class 1 integrons were present in >50% of the environmental bacterial isolates that were resistant to multiple antibiotics. This class of integrons is capable of transferring genes responsible for resistance to beta-lactam, aminoglycoside, sulfonamide and quaternary ammonium antimicrobial agents. Conjugate plasmids were also isolated, but from a small percentage of isolates. This study showed that the Mhlathuze River (a) is a medium for the spread of bacterial antibiotic resistance genes, (b) acts as a reservoir for these genes and (c) due to socio-economic pressures, may play a role in the development and evolution of these genes along this river system.200415318485
340930.9999Antibiotic resistance genes in the bacteriophage DNA fraction of environmental samples. Antibiotic resistance is an increasing global problem resulting from the pressure of antibiotic usage, greater mobility of the population, and industrialization. Many antibiotic resistance genes are believed to have originated in microorganisms in the environment, and to have been transferred to other bacteria through mobile genetic elements. Among others, β-lactam antibiotics show clinical efficacy and low toxicity, and they are thus widely used as antimicrobials. Resistance to β-lactam antibiotics is conferred by β-lactamase genes and penicillin-binding proteins, which are chromosomal- or plasmid-encoded, although there is little information available on the contribution of other mobile genetic elements, such as phages. This study is focused on three genes that confer resistance to β-lactam antibiotics, namely two β-lactamase genes (blaTEM and blaCTX-M9) and one encoding a penicillin-binding protein (mecA) in bacteriophage DNA isolated from environmental water samples. The three genes were quantified in the DNA isolated from bacteriophages collected from 30 urban sewage and river water samples, using quantitative PCR amplification. All three genes were detected in the DNA of phages from all the samples tested, in some cases reaching 104 gene copies (GC) of blaTEM or 102 GC of blaCTX-M and mecA. These values are consistent with the amount of fecal pollution in the sample, except for mecA, which showed a higher number of copies in river water samples than in urban sewage. The bla genes from phage DNA were transferred by electroporation to sensitive host bacteria, which became resistant to ampicillin. blaTEM and blaCTX were detected in the DNA of the resistant clones after transfection. This study indicates that phages are reservoirs of resistance genes in the environment.201121390233
336940.9999On sulfonamide resistance, sul genes, class 1 integrons and their horizontal transfer in Escherichia coli. Class 1 integrons (Int1) contribute to antibiotic multiresistance in Gram-negative bacteria. Being frequently carried by conjugative plasmids, their spread would depend to some extent on their horizontal transfer to other bacteria. This was the main issue that was addressed in this work: the analysis of Int1 lateral transfer in the presence of different antibiotic pressures. Strains from a previously obtained collection of Escherichia coli K12 carrying natural Int1(+) conjugative plasmids were employed as Int1 donors in conjugation experiments. Two recipient strains were used: an E. coli K12 and an uropathogenic E. coli isolate. The four antibiotics employed to select transconjugants in LB solid medium were ampicillin, trimethoprim, sulfamethoxazole, and co-trimoxazole. For this purpose, adequate final concentrations of the three last antibiotics had to be determined. Abundant transconjugants resulted from the mating experiments and appeared in most -but not all-selective plates. In those supplemented with sulfamethoxazole or co-trimoxazole, transconjugants grew or not depending on the genetic context of the recipient strain and on the type of gene conferring sulfonamide resistance (sul1 or sul2) carried by the Int1(+) plasmid. The horizontal transfer of a recombinant plasmid bearing an Int1 was also assayed by transformation and these experiments provided further information on the viability of the Int1(+) clones. Overall, results point to the existence of constraints for the lateral transfer of Int1 among E. coli bacteria, which are particularly evidenced under the antibiotic pressure of sulfamethoxazole or of its combined formula co-trimoxazole.201931247256
355750.9999Characterization of the variable region in the class 1 integron of antimicrobial-resistant Escherichia coli isolated from surface water. Fecal bacteria are considered to be a potential reservoir of antimicrobial resistance genes in the aquatic environment and could horizontally transfer these genes to autochthonous bacteria when carried on transferable and/or mobile genetic elements. Such circulation of resistance genes constitutes a latent public health hazard. The aim of this study was to characterize the variable region of the class 1 integron and relate its genetic content to resistance patterns observed in antimicrobial-resistant Escherichia coli isolated from the surface waters of Patos Lagoon, Southern Brazil. Genetic diversity of the isolates and presence of the qacEΔ1 gene, which confers resistance to quaternary ammonium compounds, were also investigated. A total of 27 isolates were analyzed. The variable region harbored dfrA17, dfrA1 and dfrA12 genes, which confer resistance to trimethoprim, and aadA1, aadA5 and aadA22 genes that encode resistance to streptomycin/spectinomycin. Most of the isolates were considered resistant to quaternary ammonium compounds and all of them carried the qacEΔ1 gene at the 3' conserved segment of the integron. ERIC-PCR analyses of E. coli isolates that presented the integrons showed great genetic diversity, indicating diverse sources of contamination in this environment. These results suggest that fecal bacteria with class 1 integrons in aquatic environments are potentially important reservoirs of antibiotic-resistance genes and may transfer these elements to other bacteria that are capable of infecting humans.201626991286
193160.9999The level of antimicrobial resistance of sewage isolates is higher than that of river isolates in different Escherichia coli lineages. The dissemination of antimicrobial-resistant bacteria in environmental water is an emerging concern in medical and industrial settings. Here, we analysed the antimicrobial resistance of Escherichia coli isolates from river water and sewage by the use of a combined experimental phenotypic and whole-genome-based genetic approach. Among the 283 tested strains, 52 were phenotypically resistant to one or more antimicrobial agents. The E. coli isolates from the river and sewage samples were phylogenetically indistinguishable, and the antimicrobial-resistant strains were dispersedly distributed in a whole-genome-based phylogenetic tree. The prevalence of antimicrobial-resistant strains as well as the number of antimicrobials to which they were resistant were higher in sewage samples than in river samples. Antimicrobial resistance genes were more frequently detected in strains from sewage samples than in those from river samples. We also found that 16 river isolates that were classified as Escherichia cryptic clade V were susceptible to all the antimicrobials tested and were negative for antimicrobial resistance genes. Our results suggest that E. coli strains may acquire antimicrobial resistance genes more frequently and/or antimicrobial-resistant E. coli strains may have higher rates of accumulation and positive selection in sewage than in rivers, irrespective of their phylogenetic distribution.202033087784
495570.9999Evidence of extensive interspecies transfer of integron-mediated antimicrobial resistance genes among multidrug-resistant Enterobacteriaceae in a clinical setting. Multidrug resistance in gram-negative bacteria appears to be primarily the result of the acquisition of resistance genes by horizontal transfer. To what extent horizontal transfer may be responsible for the emergence of multidrug resistance in a clinical setting, however, has rarely been investigated. Therefore, the integron contents of isolates collected during a nosocomial outbreak of genotypically unrelated multidrug-resistant Enterobacteriaceae were characterized. The integron was chosen as a marker of transfer because of its association with multiresistance. Some genotypically identical isolates harbored different integrons. Grouping patients carrying the same integron yielded 6 epidemiologically linked clusters, with each cluster representing a different integron. Several patients carried multiple species harboring the same integron. Conjugation experiments with these strains resulted in the transfer of complete resistance patterns at high frequencies (10(-2) to 10(-4)). These findings provide strong evidence that the horizontal transfer of resistance genes contributed largely to the emergence of multidrug-resistant Enterobacteriaceae in this clinical setting.200212089661
344780.9999The Impact of Urban Pollution on Plasmid-Mediated Resistance Acquisition in Enterobacteria from a Tropical River. Background: The exposure of environmental bacteria to contaminants in aquatic ecosystems accelerates the dissemination of antibiotic-resistance genes (ARGs) through horizontal gene transfer (HGT). Methods: In this study, we sampled three locations along a contamination gradient of a polluted river, focusing on isolating Enterobacteria from the surface waters to investigate the relationship between urban pollution and antibiotic resistance. The genomes of 15 isolates (5 per site) were sequenced to identify plasmid-borne ARGs and their association with resistance phenotypes. Results: Isolates from the site with the highest contamination (Site 3) showeda larger number of ARGs, plasmids, and resistance phenotypes. Notably, one of the isolates analyzed, E. coli A231-12, exhibited phenotypic resistance to seven antibiotics, presumably conferred by a single plasmid carrying 12 ARGs. Comparative analysis of this plasmid revealed its close evolutionary relationship with another IncH plasmid hosted by Salmonella enterica, underscoring its high ARG burden in the aquatic environment. Other plasmids identified in our isolates carried sul and dfrA genes, conferring resistance to trimethoprim/sulfamethoxazole, a commonly prescribed antibiotic combination in clinical settings. Conclusions: These results highlight the critical need to expand research on the link between pollution and plasmid-mediated antimicrobial resistance in aquatic ecosystems, which can act as reservoirs of ARGs.202439596782
340690.9999Environmental and Pathogenic Carbapenem Resistant Bacteria Isolated from a Wastewater Treatment Plant Harbour Distinct Antibiotic Resistance Mechanisms. Wastewater treatment plants are important reservoirs and sources for the dissemination of antibiotic resistance into the environment. Here, two different groups of carbapenem resistant bacteria-the potentially environmental and the potentially pathogenic-were isolated from both the wastewater influent and discharged effluent of a full-scale wastewater treatment plant and characterized by whole genome sequencing and antibiotic susceptibility testing. Among the potentially environmental isolates, there was no detection of any acquired antibiotic resistance genes, which supports the idea that their resistance mechanisms are mainly intrinsic. On the contrary, the potentially pathogenic isolates presented a broad diversity of acquired antibiotic resistance genes towards different antibiotic classes, especially β-lactams, aminoglycosides, and fluoroquinolones. All these bacteria showed multiple β-lactamase-encoding genes, some with carbapenemase activity, such as the bla(KPC)-type genes found in the Enterobacteriaceae isolates. The antibiotic susceptibility testing assays performed on these isolates also revealed that all had a multi-resistance phenotype, which indicates that the acquired resistance is their major antibiotic resistance mechanism. In conclusion, the two bacterial groups have distinct resistance mechanisms, which suggest that the antibiotic resistance in the environment can be a more complex problematic than that generally assumed.202134572700
3391100.9999Phenotypic and genotypic analysis of bacteria isolated from three municipal wastewater treatment plants on tetracycline-amended and ciprofloxacin-amended growth media. AIMS: The goal of this study was to determine the antimicrobial susceptibility of bacteria isolated from three municipal wastewater treatment plants. METHODS AND RESULTS: Numerous bacterial strains were isolated from three municipal wastewater treatment facilities on tetracycline- (n=164) and ciprofloxacin-amended (n=65) growth media. These bacteria were then characterized with respect to their resistance to as many as 10 different antimicrobials, the presence of 14 common genes that encode resistance to tetracycline, the presence of integrons and/or the ability to transfer resistance via conjugation. All of the characterized strains exhibited some degree of multiple antimicrobial resistance, with nearly 50% demonstrating resistance to every antimicrobial that was tested. Genes encoding resistance to tetracycline were commonly detected among these strains, although intriguingly the frequency of detection was slightly higher for the bacteria isolated on ciprofloxacin-amended growth media (62%) compared to the bacteria isolated on tetracycline-amended growth media (53%). Class 1 integrons were also detected in 100% of the queried tetracycline-resistant bacteria and almost half of the ciprofloxacin-resistant strains. Conjugation experiments demonstrated that at least one of the tetracycline-resistant bacteria was capable of lateral gene transfer. CONCLUSIONS: Our results demonstrate that multiple antimicrobial resistance is a common trait among tetracycline-resistant and ciprofloxacin-resistant bacteria in municipal wastewater. SIGNIFICANCE AND IMPACT OF THE STUDY: These organisms are potentially important in the proliferation of antimicrobial resistance because they appear to have acquired multiple genetic determinants that confer resistance and because they have the potential to laterally transfer these genetic determinants to strains of clinical importance.201020629799
3370110.9999Microbiological contamination and resistance genes in biofilms occurring during the drinking water treatment process. Biofilms are the predominant mode of microbial growth in drinking water systems. A dynamic exchange of individuals occurs between the attached and planktonic populations, while lateral gene transfer mediates genetic exchange in these bacterial communities. Integrons are important vectors for the spread of antimicrobial resistance. The presence of class 1 integrons (intI1, qac and sul genes) was assessed in biofilms occurring throughout the drinking water treatment process. Isolates from general and specific culture media, covering a wide range of environmental bacteria, fecal indicators and opportunistic pathogens were tested. From 96 isolates tested, 9.37% were found to possess genetic determinants of putative antimicrobial resistance, and these occurred in both Gram-positive and Gram-negative bacteria. Class 1 integron integrase gene was present in 8.33% of bacteria, all positive for the qacEΔ1 gene. The sul1 gene was present in 3.12% of total isolates, representing 37.5% of the class 1 integron positive cells. The present study shows that biofilm communities in a drinking water treatment plant are a reservoir of class 1 integrons, mainly in bacteria that may be associated with microbiological contamination. Eight out of nine integron bearing strains (88.8%) were identified based on 16S rRNA gene sequencing as either enteric bacteria or species that may be connected to animal and anthropogenic disturbance.201323247295
1972120.9999Draft Genome Sequences of Multidrug-Resistant Escherichia coli Isolated from River Water. The spread of antibiotic resistance poses a critical challenge worldwide. Contaminated environments can become reservoirs, spreading antibiotic-resistant bacteria and genetic determinants of resistance to humans directly or indirectly. Here, we report the draft genome sequence, the resistome, virulence genes, and sequence types of seven multidrug-resistant Escherichia coli strains isolated from river water.202236222705
3355130.9999Occurrence and characterization of plasmid-encoded qnr genes in quinolone-resistant bacteria across diverse aquatic environments in southern Ontario. Antimicrobial resistance is an ever-increasing threat. The widespread usage of ciprofloxacin has led to the manifestation of resistance due to chromosomal mutations or the acquisition of plasmid-mediated quinolone resistance (PMQR) traits. Some particular PMQR traits, qnr genes, have been identified globally in clinical and environmental isolates. This study aimed to determine the prevalence of ciprofloxacin-resistant bacteria in aquatic environments in southern Ontario and investigate the extent of dissemination of ciprofloxacin resistance traits among the bacterial communities. We surveyed the prevalence of plasmid encoding qnr genes using a multiplex PCR assay of associated PMQR genes, qnrA, qnrB, and qnrS, on 202 isolates. Despite the absence of significant impacts on minimum inhibitory concentration levels, the presence of qnr genes correlates with heightened resistance to quinolones and nalidixic acid in some isolates. Taxonomic analysis highlights distinct differences in the composition and diversity of ciprofloxacin-sensitive (CipS) and ciprofloxacin-resistant (CipR) populations, with Proteobacteria dominating both groups. Importantly, CipR populations exhibit lower genetic diversity but higher prevalence of multiple antibiotic resistances, suggesting co-selection mechanisms. Co-occurrence analysis highlights significant associations between ciprofloxacin resistance and other antibiotic resistances, implicating complex genetic linkages. The results of our study signified the critical role of environmental monitoring in public health.202439083844
3393140.9998Antibiotic resistance of gram-negative bacteria in rivers, United States. Bacteria with intrinsic resistance to antibiotics are found in nature. Such organisms may acquire additional resistance genes from bacteria introduced into soil or water, and the resident bacteria may be the reservoir or source of widespread resistant organisms found in many environments. We isolated antibiotic-resistant bacteria in freshwater samples from 16 U.S. rivers at 22 sites and measured the prevalence of organisms resistant to beta-lactam and non-beta-lactam antibiotics. Over 40% of the bacteria resistant to more than one antibiotic had at least one plasmid. Ampicillin resistance genes, as well as other resistance traits, were identified in 70% of the plasmids. The most common resistant organisms belonged to the following genera: Acinetobacter, Alcaligenes, Citrobacter, Enterobacter, Pseudomonas, and Serratia.200212095440
3561150.9998Isolation of novel IncA/C and IncN fluoroquinolone resistance plasmids from an antibiotic-polluted lake. OBJECTIVES: Antibiotic-polluted environments may function as reservoirs for novel resistance plasmids not yet encountered in pathogens. The aims of this study were to assess the potential of resistance transfer between bacteria from such environments and Escherichia coli, and to characterize the conjugative elements involved. METHODS: Sediment samples from Kazipally lake and Asanikunta tank, two Indian lakes with a history of severe pollution with fluoroquinolones, were investigated. Proportions of resistant bacteria were determined by selective cultivation, while horizontal gene transfer was studied using a GFP-tagged E. coli as recipient. Retrieved transconjugants were tested for susceptibility by Etest(®) and captured conjugative resistance elements were characterized by WGS. RESULTS: The polluted lakes harboured considerably higher proportions of ciprofloxacin-resistant and sulfamethoxazole-resistant bacteria than did other Indian and Swedish lakes included for comparison (52% versus 2% and 60% versus 7%, respectively). Resistance plasmids were captured from Kazipally lake, but not from any of the other lakes; in the case of Asanikunta tank because of high sediment toxicity. Eight unique IncA/C and IncN resistance plasmids were identified among 11 sequenced transconjugants. Five plasmids were fully assembled, and four of these carried the quinolone resistance gene qnrVC1, which has previously only been found on chromosomes. Acquired resistance genes, in the majority of cases associated with class 1 integrons, could be linked to decreased susceptibility to several different classes of antibiotics. CONCLUSIONS: Our study shows that environments heavily polluted with antibiotics contain novel multiresistance plasmids transferrable to E. coli.201526124213
3364160.9998Conjugative transfer of multi-drug resistance IncN plasmids from environmental waterborne bacteria to Escherichia coli. Watersheds contaminated with municipal, hospital, and agricultural residues are recognized as reservoirs for bacteria carrying antibiotic resistance genes (ARGs). The objective of this study was to determine the potential of environmental bacterial communities from the highly contaminated La Paz River basin in Bolivia to transfer ARGs to an Escherichia coli lab strain used as the recipient. Additionally, we tested ZnSO(4) and CuSO(4) at sub-inhibitory concentrations as stressors and analyzed transfer frequencies (TFs), diversity, richness, and acquired resistance profiles. The bacterial communities were collected from surface water in an urban site close to a hospital and near an agricultural area. High transfer potentials of a large set of resistance factors to E. coli were observed at both sites. Whole-genome sequencing revealed that putative plasmids belonging to the incompatibility group N (IncN, IncN2, and IncN3) were predominant among the transconjugants. All IncN variants were verified to be mobile by a second conjugation step. The plasmid backbones were similar to other IncN plasmids isolated worldwide and carried a wide range of ARGs extensively corroborated by phenotypic resistance patterns. Interestingly, all transconjugants also acquired the class 1 integron intl1, which is commonly known as a proxy for anthropogenic pollution. The addition of ZnSO(4) and CuSO(4) at sub-inhibitory concentrations did not affect the transfer rate. Metal resistance genes were absent from most transconjugants, suggesting a minor role, if any, of metals in the spread of multidrug-resistant plasmids at the investigated sites.202236386654
3382170.9998Patterns and persistence of antibiotic resistance in faecal indicator bacteria from freshwater recreational beaches. AIMS: This study was conducted to determine antibiotic susceptibility patterns among the faecal indicator bacteria (FIB), Escherichia coli and enterococci, and to determine the potential for freshwater beaches to serve as reservoirs of resistance genes where transfer of resistant phenotypes takes place or de novo resistance may evolve. METHODS AND RESULTS: One hundred and forty-seven E. coli and 150 enterococci collected from sand and water at recreational beaches along Lake Huron, Michigan, USA were screened against commonly used antibiotics. Resistance was apparent in both E. coli (19% resistant) and enterococci (65% resistant). Antibiotic-resistant E. coli were capable of growing in beach sand microcosms and were able to transfer a plasmid-encoded kanamycin-resistance gene in sand microcosms. Furthermore, resistant phenotypes were stable in the sand environment even in the absence of the corresponding antibiotic. CONCLUSIONS: Antibiotic-resistant FIB were prevalent and persistent in the beach habitat. SIGNIFICANCE AND IMPACT OF THE STUDY: Active populations of FIB at beaches express antibiotic resistance phenotypes and have the ability to transfer antibiotic resistance. These human-associated bacteria may be intermediaries in the movement of resistance between environmental and clinical reservoirs.201424698413
2569180.9998Investigating the impact of hospital antibiotic usage on aquatic environment and aquaculture systems: A molecular study of quinolone resistance in Escherichia coli. Quinolones are one of the most important classes of antibacterials available for the treatment of infectious diseases in humans. However, there is a growing concern about bacterial resistance to antimicrobials including quinolones. The spread of antibiotic-resistant bacteria in the aquatic environment has been recognized as a growing threat to public health and hospitals appear to be a major contributor to this. The objective of this study was to investigate the prevalence of quinolone resistance in Escherichia coli from selected water bodies receiving direct hospital effluents in Kerala, India. Standard disc diffusion and E-test were used for antibiotic susceptibility testing. As antibiotic resistance can develop in bacterial isolates by different means, EtBr Agar Cartwheel method was used to detect the efflux pump activity and presence of resistant genes was detected by PCR. The mechanism of transfer of plasmid mediated resistance was confirmed by conjugation experiments. A total of 209 multidrug-resistant Escherichia coli were isolated from different hospital effluent discharge sites and aquaculture farms located in their vicinity. Among them, qnrB was found to be most prevalent followed by qnrS, OqxAB, qnrA and aac (6')-Ib-cr. The results suggested that the antibiotics present at sub-inhibitory concentrations in direct hospital effluents increases the selection pressure impacting the cell function of even normal microorganisms in the aquatic environment to change the genetic expression of virulence factors or acquire resistance genes by different transfer mechanisms, posing a serious threat to public health.202032805571
3357190.9998Detection of 140 clinically relevant antibiotic-resistance genes in the plasmid metagenome of wastewater treatment plant bacteria showing reduced susceptibility to selected antibiotics. To detect plasmid-borne antibiotic-resistance genes in wastewater treatment plant (WWTP) bacteria, 192 resistance-gene-specific PCR primer pairs were designed and synthesized. Subsequent PCR analyses on total plasmid DNA preparations obtained from bacteria of activated sludge or the WWTP's final effluents led to the identification of, respectively, 140 and 123 different resistance-gene-specific amplicons. The genes detected included aminoglycoside, beta-lactam, chloramphenicol, fluoroquinolone, macrolide, rifampicin, tetracycline, trimethoprim and sulfonamide resistance genes as well as multidrug efflux and small multidrug resistance genes. Some of these genes were only recently described from clinical isolates, demonstrating genetic exchange between clinical and WWTP bacteria. Sequencing of selected resistance-gene-specific amplicons confirmed their identity or revealed that the amplicon nucleotide sequence is very similar to a gene closely related to the reference gene used for primer design. These results demonstrate that WWTP bacteria are a reservoir for various resistance genes. Moreover, detection of about 64 % of the 192 reference resistance genes in bacteria obtained from the WWTP's final effluents indicates that these resistance determinants might be further disseminated in habitats downstream of the sewage plant.200919389756