Antibiotic-resistance and virulence genes in Enterococcus isolated from tropical recreational waters. - Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
339901.0000Antibiotic-resistance and virulence genes in Enterococcus isolated from tropical recreational waters. The prevalence of enterococci harboring tetracycline- and vancomycin-resistance genes, as well as the enterococcal surface protein (esp) has mostly been determined in clinical settings, but their prevalence in tropical recreational waters remains largely unknown. The present study determined the prevalence of tetM (tetracycline-resistance), vanA and vanB (vancomycin-resistance) in the bacterial and viral fractions, enterococci and their induced phages isolated from tropical recreational marine and fresh waters, dry and wet sands. Since lysogenic phages can act as vectors for antibiotic-resistance and virulence factors, the prevalence of the mentioned genes, as well as that of an integrase-encoding gene (int) specific for Enterococcus faecalis phages was determined. Up to 60 and 54% of the bacterial fractions and enterococci, respectively, harbored at least one of the tested genes suggesting that bacteria in tropical environments may be reservoirs of antibiotic-resistance and virulence genes. int was detected in the viral fractions and in one Enterococcus isolate after induction. This study presents the opportunity to determine if the presence of bacteria harboring antibiotic-resistance and virulence genes in tropical recreational waters represents a threat to public health.201323981868
337010.9999Microbiological 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
338220.9999Patterns 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
340030.9999Chicken liver is a potential reservoir of bacteriophages and phage-derived particles containing antibiotic resistance genes. Poultry meat production is one of the most important agri-food industries in the world. The selective pressure exerted by widespread prophylactic or therapeutic use of antibiotics in intensive chicken farming favours the development of drug resistance in bacterial populations. Chicken liver, closely connected with the intestinal tract, has been directly involved in food-borne infections and found to be contaminated with pathogenic bacteria, including Campylobacter and Salmonella. In this study, 74 chicken livers, divided into sterile and non-sterile groups, were analysed, not only for microbial indicators but also for the presence of phages and phage particles containing antibiotic resistance genes (ARGs). Both bacteria and phages were detected in liver tissues, including those dissected under sterile conditions. The phages were able to infect Escherichia coli and showed a Siphovirus morphology. The chicken livers contained from 10(3) to 10(6) phage particles per g, which carried a range of ARGs (bla(TEM) , bla(CTx-M-1) , sul1, qnrA, armA and tetW) detected by qPCR. The presence of phages in chicken liver, mostly infecting E. coli, was confirmed by metagenomic analysis, although this technique was not sufficiently sensitive to identify ARGs. In addition, ARG-carrying phages were detected in chicken faeces by qPCR in a previous study of the group. Comparison of the viromes of faeces and liver showed a strong coincidence of species, which suggests that the phages found in the liver originate in faeces. These findings suggests that phages, like bacteria, can translocate from the gut to the liver, which may therefore constitute a potential reservoir of antibiotic resistance genes.202235485188
193340.9999Antibiotic Resistance Genes Occurrence in Conventional and Antibiotic-Free Poultry Farming, Italy. Antimicrobial resistance is a complex and widespread problem threatening human and animal health. In poultry farms, a wide distribution of resistant bacteria and their relative genes is described worldwide, including in Italy. In this paper, a comparison of resistance gene distribution in litter samples, recovered from four conventional and four antibiotic-free broiler flocks, was performed to highlight any influence of farming systems on the spreading and maintenance of resistance determinants. Conventional PCR tests, targeting the resistance genes related to the most used antibiotics in poultry farming, along with some critically important antibiotics for human medicine, were applied. In conventional farms, n. 10 out of n. 30 investigated genes were present in at least one sample, the most abundant fragments being the tet genes specific for tetracyclines, followed by those for aminoglycosides and chloramphenicol. All conventional samples resulted negative for colistin, carbapenems, and vancomycin resistance genes. A similar trend was observed for antibiotic-free herds, with n. 13 out of n. 30 amplified genes, while a positivity for the mcr-1 gene, specific for colistin, was observed in one antibiotic-free flock. The statistical analysis revealed a significant difference for the tetM gene, which was found more frequently in the antibiotic-free category. The analysis carried out in this study allowed us to obtain new data about the distribution of resistance patterns in the poultry industry in relation to farming types. The PCR test is a quick and non-expensive laboratory tool for the environmental monitoring of resistance determinants identifying potential indicators of AMR dissemination.202236139170
341050.9999vanA Gene Harboring Enterococcal and Non-enterococcal Isolates Expressing High Level Vancomycin and Teicoplanin Resistance Reservoired in Surface Waters. Untreated wastewaters and treated effluents even after final disinfection contain antibiotic resistant bacteria and resistance genes before they are released into surface waters. A correlation between resistant bacteria and antibiotics in surface waters has been found, as have antibiotic resistance genes. Of particular interest are vancomycin-resistant enterococci harboring vanA gene that confers high level of resistance to glycopeptide antibiotics including teicoplanin. Therefore, in this study, river water samples were analysed to investigate vancomycin- and teicoplanin-resistant bacterial isolates harboring vanA gene. Out of 290, 15 surface water isolates displayed resistance to both antibiotics. These glycopeptide resistant enterococcal and non-enterococcal isolates, identified by 16S rRNA sequencing, were found to harbor vanA gene with sequence similarities of 50 % to 100 %. The presence of D-alanine-D-lactate ligase encoded by vanA gene was also shown for all vancomycin- and teicoplanin-resistant isolates through western blot analysis. Due to reuse of treated wastewater and release of untreated wastewaters to water bodies, antibiotic resistant bacteria and resistance genes are being introduced into surface waters and present human health risks. Therefore, surface waters are not only hot spots for vanA harboring enterococcal isolates but also non-enterococcal isolates due to gene dissemination and require special scientific consideration.201727770152
340260.9999Antibiotic resistance, virulence factors and biofilm formation ability in Escherichia coli strains isolated from chicken meat and wildlife in the Czech Republic. Attachment of pathogenic bacteria to food contact surfaces and the subsequent biofilm formation represent a serious threat for the food industry, since these bacteria are more resistant to antimicrobials or possess more virulence factors. The main aim of this study was to investigate the correlation between antibiotic resistance against 13 antibiotics, distribution of 10 virulence factors and biofilm formation in 105 Escherichia coli strains according to their origin. The high prevalence of antibiotic resistance that we have found in wildlife isolates could be acquired by horizontal transfer of resistance genes from human or domestic or farm animals. Consequently, these commensal bacteria might serve as indicator of antimicrobial usage for human and veterinary purposes in the Czech Republic. Further, 46 out of 66 resistant isolates (70%) were able to form biofilm and we found out statistically significant correlation between prevalence of antibiotic resistance and biofilm formation ability. The highest prevalence of antibiotic resistance was observed in weak biofilm producers. Biofilm formation was not statistically associated with any virulence determinant. However, we confirmed the correlation between prevalence of virulence factors and host origin. Chicken isolates possessed more virulence factors (66%), than isolates from wildlife (37%). We can conclude that the potential spread of antibiotic resistance pattern via the food chain is of high concern for public health. Even more, alarming is that E. coli isolates remain pathogenic potential with ability to form biofilm and these bacteria may persist during food processing and consequently lead to greater risks of food contamination.201728494209
340970.9999Antibiotic 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
281480.9999Fate of antimicrobial-resistant enterococci and staphylococci and resistance determinants in stored poultry litter. The use of antimicrobials in commercial broiler poultry production results in the presence of drug-resistant bacteria shed in the excreta of these birds. Because these wastes are largely land-disposed these pathogens can affect the surrounding environment and population. In this analysis, we characterized the survival of antimicrobial-resistant enterococci and staphylococci and resistance genes in poultry litter. Temperature, moisture, and pH were measured in the litter over a 120-day period from storage sheds at three conventional US broiler chicken farms, as well as colony-forming units of Enterococcus spp. and Staphylococcus spp. Selected isolates from each sampling event were tested for resistance to eight antimicrobials used in poultry feeds as well as the presence of resistance genes and mobile genetic elements. Temperatures greater than 60 degrees C were only intermittently observed in the core of the litter piles. Both antimicrobial-resistant enterococci and staphylococci, as well as resistance genes persisted throughout the 120-day study period. Resistance genes identified in the study include: erm(A), erm(B), erm (C), msr(A/B), msr(C), and vat(E). This study indicates that typical storage practices of poultry litter are insufficient for eliminating drug-resistant enterococci and staphylococci, which may then be released into the environment through land disposal.200919541298
339890.9999Ubiquity of R factor-mediated antibiotic resistance in the healthy population. An attempt was made to assess the occurrence of R factor-mediated antibiotic resistance in the healthy population. Samples of aerobic, gram-negative intestinal bacteria from men from various parts of the country at military conscription were analysed for transferable drug resistance. The obtained frequency, about 15% of R factor carriers in the studied group, was interpreted to reflect the existence of a reservoir of R factors, from which resistant, pathogenic bacteria could be selected under antibiotic therapy. Resistance to tetracycline, streptomycin and sulfonamides dominated among the identified R factor-borne resistance traits.1977320655
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
3394110.9999Antibiotic 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
3386120.9999Occurrence and patterns of antibiotic resistance in vertebrates off the Northeastern United States coast. The prevalence of antibiotic-resistant bacteria in the marine environment is a growing concern, but the degree to which marine mammals, seabirds and fish harbor these organisms is not well documented. This project sought to identify the occurrence and patterns of antibiotic resistance in bacteria isolated from vertebrates of coastal waters in the northeastern United States. Four hundred and seventy-two isolates of clinical interest were tested for resistance to a suite of 16 antibiotics. Fifty-eight percent were resistant to at least one antibiotic, while 43% were resistant to multiple antibiotics. A multiple antibiotic resistance index value >or=0.2 was observed in 38% of the resistant pathogens, suggesting exposure of the animals to bacteria from significantly contaminated sites. Groups of antibiotics were identified for which bacterial resistance commonly co-occurred. Antibiotic resistance was more widespread in bacteria isolated from seabirds than marine mammals, and was more widespread in stranded or bycaught marine mammals than live marine mammals. Structuring of resistance patterns based on sample type (live/stranded/bycaught) but not animal group (mammal/bird/fish) was observed. These data indicate that antibiotic resistance is widespread in marine vertebrates, and they may be important reservoirs of antibiotic-resistant bacteria in the marine environment.200919187217
3696130.9999Assessment of Tetracyclines Residues and Tetracycline Resistant Bacteria in Conventional and Organic Baby Foods. Children are very vulnerable to bacterial infections and they are sometimes subject to antimicrobials for healing. The presence of resistance genes may counteract effects of antimicrobials. This work has thereby compared the amount of tetracycline resistance genes, tet(A) and tet(B), between conventional and organic meat-based or vegetable-based baby foods and used the quantification of these genes to assess the presence of tetracycline residues in these samples. Counts of bacteria harboring the tet(A) gene were higher than those containing tet(B), and there was no difference between the organic and the conventional samples. Samples with detectable amounts of tetracycline residues were also positive for the presence of tet genes, and when the presence of the genes was not detected, the samples were also negative for the presence of residues. The percentages of tetracycline residues were higher in organic samples than in conventional ones. It cannot be concluded that organic formulas are safer than conventional ones for the studied parameters.201528231206
3606140.9999Presence of specific antibiotic (tet) resistance genes in infant faecal microbiota. The widespread use of antibiotics for medical and veterinary purposes has led to an increase of microbial resistance. The antibiotic resistance of pathogenic bacteria has been studied extensively. However, antibiotics are not only selective for pathogens: they also affect all members of the gut microbiota. These microorganisms may constitute a reservoir of genes carrying resistance to specific antibiotics. This study was designed to characterize the gut microbiota with regard to the presence of genes encoding tetracycline resistance proteins (tet) in the gut of healthy exclusively breast-fed infants and their mothers. For this purpose we determined the prevalence of genes encoding ribosomal protection proteins (tet M, tet W, tet O, tet S, tet T and tet B) by PCR and characterized the gut microbiota by FISH in stools of infants and their mothers. The gene tet M was found in all the breast-fed infants and their mothers. tet O was found in all of the mothers' samples, whilst only 35% of the infants harboured this gene. tet W was less frequently found (85% of the mothers and 13% of the infants). None of the other genes analysed was found in any sample. Our results suggest that genes carrying antibiotic resistance are common in the environment, as even healthy breast-fed infants with no direct or indirect previous exposure to antibiotics harbour these genes.200616965348
3697150.9999Aquaculture can promote the presence and spread of antibiotic-resistant Enterococci in marine sediments. Aquaculture is an expanding activity worldwide. However its rapid growth can affect the aquatic environment through release of large amounts of chemicals, including antibiotics. Moreover, the presence of organic matter and bacteria of different origin can favor gene transfer and recombination. Whereas the consequences of such activities on environmental microbiota are well explored, little is known of their effects on allochthonous and potentially pathogenic bacteria, such as enterococci. Sediments from three sampling stations (two inside and one outside) collected in a fish farm in the Adriatic Sea were examined for enterococcal abundance and antibiotic resistance traits using the membrane filter technique and an improved quantitative PCR. Strains were tested for susceptibility to tetracycline, erythromycin, ampicillin and gentamicin; samples were directly screened for selected tetracycline [tet(M), tet(L), tet(O)] and macrolide [erm(A), erm(B) and mef] resistance genes by newly-developed multiplex PCRs. The abundance of benthic enterococci was higher inside than outside the farm. All isolates were susceptible to the four antimicrobials tested, although direct PCR evidenced tet(M) and tet(L) in sediment samples from all stations. Direct multiplex PCR of sediment samples cultured in rich broth supplemented with antibiotic (tetracycline, erythromycin, ampicillin or gentamicin) highlighted changes in resistance gene profiles, with amplification of previously undetected tet(O), erm(B) and mef genes and an increase in benthic enterococcal abundance after incubation in the presence of ampicillin and gentamicin. Despite being limited to a single farm, these data indicate that aquaculture may influence the abundance and spread of benthic enterococci and that farm sediments can be reservoirs of dormant antibiotic-resistant bacteria, including enterococci, which can rapidly revive in presence of new inputs of organic matter. This reservoir may constitute an underestimated health risk and deserves further investigation.201323638152
3375160.9999Occurrence of antimicrobial agents, drug-resistant bacteria, and genes in the sewage-impacted Vistula River (Poland). Antimicrobial agents (antimicrobials) are a group of therapeutic and hygienic agents that either kill microorganisms or inhibit their growth. Their occurrence in surface water may reveal harmful effects on aquatic biota and challenge microbial populations. Recently, there is a growing concern over the contamination of surface water with both antimicrobial agents and multidrug-resistant bacteria. The aim of the study was the determination of the presence of selected antimicrobials at specific locations of the Vistula River (Poland), as well as in tap water samples originating from the Warsaw region. Analysis was performed using the liquid chromatography-electrospray ionization-tandem mass spectrometry method. In addition, the occurrence of drug-resistant bacteria and resistance genes was determined using standard procedures. This 2-year study is the first investigation of the simultaneous presence of antimicrobial agents, drug-resistant bacteria, and genes in Polish surface water. In Poland, relatively high concentrations of macrolides are observed in both surface and tap water. Simultaneous to the high macrolide levels in the environment, the presence of the erm B gene, coding the resistance to macrolides, lincosamides, and streptogramin, was detected in almost all sampling sites. Another ubiquitous gene was int1, an element of the 5'-conserved segment of class 1 integrons that encode site-specific integrase. Also, resistant isolates of Enterococcus faecium and Enterococcus faecalis and Gram-negative bacteria were recovered. Multidrug-resistant bacteria isolates of Gram-negative and Enterococcus were also detected. The results show that wastewater treatment plants (WWTP) are the main source of most antimicrobials, resistant bacteria, and genes in the aquatic environment, probably due to partial purification during wastewater treatment processes.201829235021
3401170.9999Heavy metal resistance and virulence profile in Pseudomonas aeruginosa isolated from Brazilian soils. Pseudomonas aeruginosa is an opportunistic pathogen, which can have several virulence factors that confer on it the ability to cause severe, acute and chronic infections. Thus, the simultaneous occurrence of resistance to antibiotics and heavy metals associated with the presence of virulence genes is a potential threat to human health and environmental balance. This study aimed to investigate the resistance profile to heavy metals and the correlation of this phenotype of resistance to antimicrobials and to investigate the pathogenic potential of 46 P. aeruginosa isolates obtained from the soil of five Brazilian regions. The bacteria were evaluating for antimicrobial and heavy metal resistance, as well as the presence of plasmids and virulence genes. The isolates showed resistance to four different antibiotics and the majority (n = 44) had resistance to aztreonam or ticarcillin, furthermore, 32 isolates showed concomitant resistance to both of these antibiotics. A high prevalence of virulence genes was found, which highlights the pathogenic potential of the studied environmental isolates. Moreover, a high frequency of heavy metal resistance genes was also detected, however, the phenotypic results indicated that other genes and/or mechanisms should be related to heavy metal resistance.201627197940
3383180.9999Drug resistance of coliform bacteria in hospital and city sewage. The number and properties of drug-resistant coliform bacteria in hospital and city sewage were compared. There was little difference in the counts of organisms with nontransferable resistance to one or more of 13 commonly used drugs. An average of 26% of coliforms in hospital waste water had transferable resistance to at least one of the drugs ampicillin, chloramphenicol, streptomycin, sulfonamide, or tetracycline as compared to an average of 4% in city sewage. R(+) bacteria in the hospital discharge were also resistant to a broader spectrum of drugs than those in city sewage. In both effluents, the occurrence of fecal Escherichia coli among R(+) coliforms was twice as high as among coliforms with nontransferable resistance. Resistance was transferable to Salmonella typhi, and such drug-resistant pathogens in the water environment could be of particular concern. The significance of the results with regard to environmental pollution with R(+) bacteria and the dissemination of these organisms is discussed.19734597713
3405190.9999Practical implications of erythromycin resistance gene diversity on surveillance and monitoring of resistance. Use of antibiotics in human and animal medicine has applied selective pressure for the global dissemination of antibiotic-resistant bacteria. Therefore, it is of interest to develop strategies to mitigate the continued amplification and transmission of resistance genes in environmental reservoirs such as farms, hospitals and watersheds. However, the efficacy of mitigation strategies is difficult to evaluate because it is unclear which resistance genes are important to monitor, and which primers to use to detect those genes. Here, we evaluated the diversity of one type of macrolide antibiotic resistance gene (erm) in one type of environment (manure) to determine which primers would be most informative to use in a mitigation study of that environment. We analyzed all known erm genes and assessed the ability of previously published erm primers to detect the diversity. The results showed that all known erm resistance genes group into 66 clusters, and 25 of these clusters (40%) can be targeted with primers found in the literature. These primers can target 74%-85% of the erm gene diversity in the manures analyzed.201829346541