Ecology, more than antibiotics consumption, is the major predictor for the global distribution of aminoglycoside-modifying enzymes. - Related Documents




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389001.0000Ecology, more than antibiotics consumption, is the major predictor for the global distribution of aminoglycoside-modifying enzymes. Antibiotic consumption and its abuses have been historically and repeatedly pointed out as the major driver of antibiotic resistance emergence and propagation. However, several examples show that resistance may persist despite substantial reductions in antibiotic use, and that other factors are at stake. Here, we study the temporal, spatial, and ecological distribution patterns of aminoglycoside resistance, by screening more than 160,000 publicly available genomes for 27 clusters of genes encoding aminoglycoside-modifying enzymes (AME genes). We find that AME genes display a very ubiquitous pattern: about 25% of sequenced bacteria carry AME genes. These bacteria were sequenced from all the continents (except Antarctica) and terrestrial biomes, and belong to a wide number of phyla. By focusing on European countries between 1997 and 2018, we show that aminoglycoside consumption has little impact on the prevalence of AME-gene-carrying bacteria, whereas most variation in prevalence is observed among biomes. We further analyze the resemblance of resistome compositions across biomes: soil, wildlife, and human samples appear to be central to understand the exchanges of AME genes between different ecological contexts. Together, these results support the idea that interventional strategies based on reducing antibiotic use should be complemented by a stronger control of exchanges, especially between ecosystems.202336785930
388410.9999Distribution and quantification of antibiotic resistant genes and bacteria across agricultural and non-agricultural metagenomes. There is concern that antibiotic resistance can potentially be transferred from animals to humans through the food chain. The relationship between specific antibiotic resistant bacteria and the genes they carry remains to be described. Few details are known about the ecology of antibiotic resistant genes and bacteria in food production systems, or how antibiotic resistance genes in food animals compare to antibiotic resistance genes in other ecosystems. Here we report the distribution of antibiotic resistant genes in publicly available agricultural and non-agricultural metagenomic samples and identify which bacteria are likely to be carrying those genes. Antibiotic resistance, as coded for in the genes used in this study, is a process that was associated with all natural, agricultural, and human-impacted ecosystems examined, with between 0.7 to 4.4% of all classified genes in each habitat coding for resistance to antibiotic and toxic compounds (RATC). Agricultural, human, and coastal-marine metagenomes have characteristic distributions of antibiotic resistance genes, and different bacteria that carry the genes. There is a larger percentage of the total genome associated with antibiotic resistance in gastrointestinal-associated and agricultural metagenomes compared to marine and Antarctic samples. Since antibiotic resistance genes are a natural part of both human-impacted and pristine habitats, presence of these resistance genes in any specific habitat is therefore not sufficient to indicate or determine impact of anthropogenic antibiotic use. We recommend that baseline studies and control samples be taken in order to determine natural background levels of antibiotic resistant bacteria and/or antibiotic resistance genes when investigating the impacts of veterinary use of antibiotics on human health. We raise questions regarding whether the underlying biology of each type of bacteria contributes to the likelihood of transfer via the food chain.201223133629
391220.9999Genomic Sequence Analysis of Methicillin- and Carbapenem-Resistant Bacteria Isolated from Raw Sewage. Antibiotic resistance is one of the largest threats facing global health. Wastewater treatment plants are well-known hot spots for interaction between diverse bacteria, genetic exchange, and antibiotic resistance. Nonpathogenic bacteria theoretically act as reservoirs of antibiotic resistance subsequently transferring antibiotic resistance genes to pathogens, indicating that evolutionary processes occur outside clinical settings and may drive patterns of drug-resistant infections. We isolated and sequenced 100 bacterial strains from five wastewater treatment plants to analyze regional dynamics of antibiotic resistance in the California Central Valley. The results demonstrate the presence of a wide diversity of pathogenic and nonpathogenic bacteria, with an arithmetic mean of 5.1 resistance genes per isolate. Forty-three percent of resistance genes were located on plasmids, suggesting that large levels of gene transfer between bacteria that otherwise may not co-occur are facilitated by wastewater treatment. One of the strains detected was a Bacillus carrying pX01 and pX02 anthrax-like plasmids and multiple drug resistance genes. A correlation between resistance genes and taxonomy indicates that taxon-specific evolutionary studies may be useful in determining and predicting patterns of antibiotic resistance. Conversely, a lack of geographic correlation may indicate that landscape genetic studies to understand the spread of antibiotic resistance genes should be carried out at broader scales. This large data set provides insights into how pathogenic and nonpathogenic bacteria interact in wastewater environments and the resistance genes which may be horizontally transferred between them. This can help in determining the mechanisms leading to the increasing prevalence of drug-resistant infections observed in clinical settings. IMPORTANCE The reasons for the increasing prevalence of antibiotic-resistant infections are complex and associated with myriad clinical and environmental processes. Wastewater treatment plants operate as nexuses of bacterial interaction and are known hot spots for genetic exchange between bacteria, including antibiotic resistance genes. We isolated and sequenced 100 drug-resistant bacteria from five wastewater treatment plants in California's Central Valley, characterizing widespread gene sharing between pathogens and nonpathogens. We identified a novel, multiresistant Bacillus carrying anthrax-like plasmids. This empirical study supports the likelihood of evolutionary and population processes in the broader environment affecting the prevalence of clinical drug-resistant infections and identifies several taxa that may operate as reservoirs and vectors of antibiotic resistance genes.202134132566
405030.9998Are Virulence and Antibiotic Resistance Genes Linked? A Comprehensive Analysis of Bacterial Chromosomes and Plasmids. Although pathogenic bacteria are the targets of antibiotics, these drugs also affect hundreds of commensal or mutualistic species. Moreover, the use of antibiotics is not only restricted to the treatment of infections but is also largely applied in agriculture and in prophylaxis. During this work, we tested the hypothesis that there is a correlation between the number and the genomic location of antibiotic resistance (AR) genes and virulence factor (VF) genes. We performed a comprehensive study of 16,632 reference bacterial genomes in which we identified and counted all orthologues of AR and VF genes in each of the locations: chromosomes, plasmids, or in both locations of the same genome. We found that, on a global scale, no correlation emerges. However, some categories of AR and VF genes co-occur preferentially, and in the mobilome, which supports the hypothesis that some bacterial pathogens are under selective pressure to be resistant to specific antibiotics, a fact that can jeopardize antimicrobial therapy for some human-threatening diseases.202235740113
389240.9998Tetracycline and Phenicol Resistance Genes and Mechanisms: Importance for Agriculture, the Environment, and Humans. Recent reports have speculated on the future impact that antibiotic-resistant bacteria will have on food production, human health, and global economics. This review examines microbial resistance to tetracyclines and phenicols, antibiotics that are widely used in global food production. The mechanisms of resistance, mode of spread between agriculturally and human-impacted environments and ecosystems, distribution among bacteria, and the genes most likely to be associated with agricultural and environmental settings are included. Forty-six different tetracycline resistance () genes have been identified in 126 genera, with (M) having the broadest taxonomic distribution among all bacteria and (B) having the broadest coverage among the Gram-negative genera. Phenicol resistance genes are organized into 37 groups and have been identified in 70 bacterial genera. The review provides the latest information on tetracycline and phenicol resistance genes, including their association with mobile genetic elements in bacteria of environmental, medical, and veterinary relevance. Knowing what specific antibiotic-resistance genes (ARGs) are found in specific bacterial species and/or genera is critical when using a selective suite of ARGs for detection or surveillance studies. As detection methods move to molecular techniques, our knowledge about which type of bacteria carry which resistance gene(s) will become more important to ensure that the whole spectrum of bacteria are included in future surveillance studies. This review provides information needed to integrate the biology, taxonomy, and ecology of tetracycline- and phenicol-resistant bacteria and their resistance genes so that informative surveillance strategies can be developed and the correct genes selected.201627065405
334350.9998Shotgun metagenomics reveals a wide array of antibiotic resistance genes and mobile elements in a polluted lake in India. There is increasing evidence for an environmental origin of many antibiotic resistance genes. Consequently, it is important to identify environments of particular risk for selecting and maintaining such resistance factors. In this study, we described the diversity of antibiotic resistance genes in an Indian lake subjected to industrial pollution with fluoroquinolone antibiotics. We also assessed the genetic context of the identified resistance genes, to try to predict their genetic transferability. The lake harbored a wide range of resistance genes (81 identified gene types) against essentially every major class of antibiotics, as well as genes responsible for mobilization of genetic material. Resistance genes were estimated to be 7000 times more abundant than in a Swedish lake included for comparison, where only eight resistance genes were found. The sul2 and qnrD genes were the most common resistance genes in the Indian lake. Twenty-six known and 21 putative novel plasmids were recovered in the Indian lake metagenome, which, together with the genes found, indicate a large potential for horizontal gene transfer through conjugation. Interestingly, the microbial community of the lake still included a wide range of taxa, suggesting that, across most phyla, bacteria has adapted relatively well to this highly polluted environment. Based on the wide range and high abundance of known resistance factors we have detected, it is plausible that yet unrecognized resistance genes are also present in the lake. Thus, we conclude that environments polluted with waste from antibiotic manufacturing could be important reservoirs for mobile antibiotic resistance genes.201425520706
464460.9998Longitudinal metatranscriptomic sequencing of Southern California wastewater representing 16 million people from August 2020-21 reveals widespread transcription of antibiotic resistance genes. Municipal wastewater provides a representative sample of human fecal waste across a catchment area and contains a wide diversity of microbes. Sequencing wastewater samples provides information about human-associated and medically-important microbial populations, and may be useful to assay disease prevalence and antimicrobial resistance (AMR). Here, we present a study in which we used untargeted metatranscriptomic sequencing on RNA extracted from 275 sewage influent samples obtained from eight wastewater treatment plants (WTPs) representing approximately 16 million people in Southern California between August 2020 - August 2021. We characterized bacterial and viral transcripts, assessed metabolic pathway activity, and identified over 2,000 AMR genes/variants across all samples. Because we did not deplete ribosomal RNA, we have a unique window into AMR carried as ribosomal mutants. We show that AMR diversity varied between WTPs and that the relative abundance of many individual AMR genes/variants increased over time and may be connected to antibiotic use during the COVID-19 pandemic. Similarly, we detected transcripts mapping to human pathogenic bacteria and viruses suggesting RNA sequencing is a powerful tool for wastewater-based epidemiology and that there are geographical signatures to microbial transcription. We captured the transcription of gene pathways common to bacterial cell processes, including central carbon metabolism, nucleotide synthesis/salvage, and amino acid biosynthesis. We also posit that due to the ubiquity of many viruses and bacteria in wastewater, new biological targets for microbial water quality assessment can be developed. To the best of our knowledge, our study provides the most complete longitudinal metatranscriptomic analysis of a large population's wastewater to date and demonstrates our ability to monitor the presence and activity of microbes in complex samples. By sequencing RNA, we can track the relative abundance of expressed AMR genes/variants and metabolic pathways, increasing our understanding of AMR activity across large human populations and sewer sheds.202235982656
334270.9998Marine sediment bacteria harbor antibiotic resistance genes highly similar to those found in human pathogens. The ocean is a natural habitat for antibiotic-producing bacteria, and marine aquaculture introduces antibiotics into the ocean to treat infections and improve aquaculture production. Studies have shown that the ocean is an important reservoir of antibiotic resistance genes. However, there is a lack of understanding and knowledge about the clinical importance of the ocean resistome. We investigated the relationship between the ocean bacterial resistome and pathogenic resistome. We applied high-throughput sequencing and metagenomic analyses to explore the resistance genes in bacterial plasmids from marine sediments. Numerous putative resistance determinants were detected among the resistance genes in the sediment bacteria. We also found that several contigs shared high identity with transposons or plasmids from human pathogens, indicating that the sediment bacteria recently contributed or acquired resistance genes from pathogens. Marine sediment bacteria could play an important role in the global exchange of antibiotic resistance.201323370726
389480.9998Novel Soil-Derived Beta-Lactam, Chloramphenicol, Fosfomycin and Trimethoprim Resistance Genes Revealed by Functional Metagenomics. Antibiotic resistance genes (ARGs) in soil are considered to represent one of the largest environmental resistomes on our planet. As these genes can potentially be disseminated among microorganisms via horizontal gene transfer (HGT) and in some cases are acquired by clinical pathogens, knowledge about their diversity, mobility and encoded resistance spectra gained increasing public attention. This knowledge offers opportunities with respect to improved risk prediction and development of strategies to tackle antibiotic resistance, and might help to direct the design of novel antibiotics, before further resistances reach hospital settings or the animal sector. Here, metagenomic libraries, which comprise genes of cultivated microorganisms, but, importantly, also those carried by the uncultured microbial majority, were screened for novel ARGs from forest and grassland soils. We detected three new beta-lactam, a so far unknown chloramphenicol, a novel fosfomycin, as well as three previously undiscovered trimethoprim resistance genes. These ARGs were derived from phylogenetically diverse soil bacteria and predicted to encode antibiotic inactivation, antibiotic efflux, or alternative variants of target enzymes. Moreover, deduced gene products show a minimum identity of ~21% to reference database entries and confer high-level resistance. This highlights the vast potential of functional metagenomics for the discovery of novel ARGs from soil ecosystems.202133916668
403390.9998Evolution and ecology of antibiotic resistance genes. A new perspective on the topic of antibiotic resistance is beginning to emerge based on a broader evolutionary and ecological understanding rather than from the traditional boundaries of clinical research of antibiotic-resistant bacterial pathogens. Phylogenetic insights into the evolution and diversity of several antibiotic resistance genes suggest that at least some of these genes have a long evolutionary history of diversification that began well before the 'antibiotic era'. Besides, there is no indication that lateral gene transfer from antibiotic-producing bacteria has played any significant role in shaping the pool of antibiotic resistance genes in clinically relevant and commensal bacteria. Most likely, the primary antibiotic resistance gene pool originated and diversified within the environmental bacterial communities, from which the genes were mobilized and penetrated into taxonomically and ecologically distant bacterial populations, including pathogens. Dissemination and penetration of antibiotic resistance genes from antibiotic producers were less significant and essentially limited to other high G+C bacteria. Besides direct selection by antibiotics, there is a number of other factors that may contribute to dissemination and maintenance of antibiotic resistance genes in bacterial populations.200717490428
3893100.9998Diverse antibiotic resistance genes in dairy cow manure. Application of manure from antibiotic-treated animals to crops facilitates the dissemination of antibiotic resistance determinants into the environment. However, our knowledge of the identity, diversity, and patterns of distribution of these antibiotic resistance determinants remains limited. We used a new combination of methods to examine the resistome of dairy cow manure, a common soil amendment. Metagenomic libraries constructed with DNA extracted from manure were screened for resistance to beta-lactams, phenicols, aminoglycosides, and tetracyclines. Functional screening of fosmid and small-insert libraries identified 80 different antibiotic resistance genes whose deduced protein sequences were on average 50 to 60% identical to sequences deposited in GenBank. The resistance genes were frequently found in clusters and originated from a taxonomically diverse set of species, suggesting that some microorganisms in manure harbor multiple resistance genes. Furthermore, amid the great genetic diversity in manure, we discovered a novel clade of chloramphenicol acetyltransferases. Our study combined functional metagenomics with third-generation PacBio sequencing to significantly extend the roster of functional antibiotic resistance genes found in animal gut bacteria, providing a particularly broad resource for understanding the origins and dispersal of antibiotic resistance genes in agriculture and clinical settings. IMPORTANCE The increasing prevalence of antibiotic resistance among bacteria is one of the most intractable challenges in 21st-century public health. The origins of resistance are complex, and a better understanding of the impacts of antibiotics used on farms would produce a more robust platform for public policy. Microbiomes of farm animals are reservoirs of antibiotic resistance genes, which may affect distribution of antibiotic resistance genes in human pathogens. Previous studies have focused on antibiotic resistance genes in manures of animals subjected to intensive antibiotic use, such as pigs and chickens. Cow manure has received less attention, although it is commonly used in crop production. Here, we report the discovery of novel and diverse antibiotic resistance genes in the cow microbiome, demonstrating that it is a significant reservoir of antibiotic resistance genes. The genomic resource presented here lays the groundwork for understanding the dispersal of antibiotic resistance from the agroecosystem to other settings.201424757214
3913110.9998Determining the prevalence, identity and possible origin of bacterial pathogens in soil. Soil biomes are vast, exceptionally diverse and crucial to the health of ecosystems and societies. Soils also contain an appreciable, but understudied, diversity of opportunistic human pathogens. With climate change and other forms of environmental degradation potentially increasing exposure risks to soilborne pathogens, it is necessary to gain a better understanding of their ecological drivers. Here we use the Galleria mellonella insect virulence model to selectively isolate pathogenic bacteria from soils in Cornwall (UK). We find a high prevalence of pathogenic soil bacteria with two genera, Providencia and Serratia, being especially common. Providencia alcalifaciens, P. rustigianii, Serratia liquefaciens and S. plymuthica strains were studied in more detail using phenotypic virulence and antibiotic resistance assays and whole-genome sequencing. Both genera displayed low levels of antibiotic resistance and antibiotic resistance gene carriage. However, Serratia isolates were found to carry the recently characterized metallo-β-lactamase blaSPR-1 that, although not conferring high levels of resistance in these strains, poses a potential risk of horizontal transfer to other pathogens where it could be fully functional. The Galleria assay can be a useful approach to uncover the distribution and identity of pathogenic bacteria in the environment, as well as uncover resistance genes with an environmental origin.202032990385
3341120.9998The shared resistome of human and pig microbiota is mobilized by distinct genetic elements. The extensive use of antibiotics in hospitals and in the animal breeding industry has promoted antibiotic resistance in bacteria, which resulted in the emergence of a large number of antibiotic resistance genes in the intestinal tract of human and farmed animals. Genetic exchange of resistance genes between the two ecosystems is now well documented for pathogenic bacteria, but the repertoire of shared resistance genes in the commensal bacterial community and by which genetic modules they are disseminated are still unclear. By analyzing metagenomics data of human and pig intestinal samples both collected in Shenzhen, China, a set of 27 highly prevalent antibiotic resistance genes was found to be shared between human and pig intestinal microbiota. The mobile genetic context for 11 of these core antibiotic resistance genes could be identified by mining their carrying scaffolds constructed from the two datasets, leading to the detection of seven integrative and conjugative/mobilizable elements and two IS-related transposons. The comparison of the relative abundances between these detected mobile genetic elements and their associated antibiotic resistance genes revealed that for many genes, the estimated contribution of the mobile elements to the gene abundance differs strikingly depending on the host. These findings indicate that although some antibiotic resistance genes are ubiquitous across microbiota of human and pig populations, they probably relied on different genetic elements for their dissemination within each population.IMPORTANCE There is growing concern that antibiotic resistance genes could spread from the husbandry environment to human pathogens through dissemination mediated by mobile genetic elements. In this study, we investigated the contribution of mobile genetic elements to the abundance of highly prevalent antibiotic resistance genes found in commensal bacteria of both human and pig intestinal microbiota originating from the same region. Our results reveal that for most of these antibiotic resistance genes, the abundance is not explained by the same mobile genetic element in each host, suggesting that the human and pig microbial communities promoted a different set of mobile genetic carriers for the same antibiotic resistance genes. These results deepen our understanding of the dissemination of antibiotic resistance genes among and between human and pig gut microbiota.202133310720
4127130.9998The Perfect Condition for the Rising of Superbugs: Person-to-Person Contact and Antibiotic Use Are the Key Factors Responsible for the Positive Correlation between Antibiotic Resistance Gene Diversity and Virulence Gene Diversity in Human Metagenomes. Human metagenomes with a high diversity of virulence genes tend to have a high diversity of antibiotic-resistance genes and vice-versa. To understand this positive correlation, we simulated the transfer of these genes and bacterial pathogens in a community of interacting people that take antibiotics when infected by pathogens. Simulations show that people with higher diversity of virulence and resistance genes took antibiotics long ago, not recently. On the other extreme, we find people with low diversity of both gene types because they took antibiotics recently-while antibiotics select specific resistance genes, they also decrease gene diversity by eliminating bacteria. In general, the diversity of virulence and resistance genes becomes positively correlated whenever the transmission probability between people is higher than the probability of losing resistance genes. The positive correlation holds even under changes of several variables, such as the relative or total diversity of virulence and resistance genes, the contamination probability between individuals, the loss rate of resistance genes, or the social network type. Because the loss rate of resistance genes may be shallow, we conclude that the transmission between people and antibiotic usage are the leading causes for the positive correlation between virulence and antibiotic-resistance genes.202134065307
4563140.9998Prophages as a source of antimicrobial resistance genes in the human microbiome. Prophages-viruses that integrate into bacterial genomes-are ubiquitous in the microbial realm. Prophages contribute significantly to horizontal gene transfer, including the potential spread of antimicrobial resistance (AMR) genes, because they can collect host genes. Understanding their role in the human microbiome is essential for fully understanding AMR dynamics and possible clinical implications. We analysed almost 15,000 bacterial genomes for prophages and AMR genes. The bacteria were isolated from diverse human body sites and geographical regions, and their genomes were retrieved from GenBank. AMR genes were detected in 6.6% of bacterial genomes, with a higher prevalence in people with symptomatic diseases. We found a wide variety of AMR genes combating multiple drug classes. We discovered AMR genes previously associated with plasmids, such as blaOXA-23 in Acinetobacter baumannii prophages or genes found in prophages in species they had not been previously described in, such as mefA-msrD in Gardnerella prophages, suggesting prophage-mediated gene transfer of AMR genes. Prophages encoding AMR genes were found at varying frequencies across body sites and geographical regions, with Asia showing the highest diversity of AMR genes.202540166311
4034150.9998Environmental and clinical antibiotic resistomes, same only different. The history of antibiotic use in the clinic is one of initial efficacy followed inevitably by the emergence of resistance. Often this resistance is the result of the capture and mobilization of genes that have their origins in environmental reservoirs. Both antibiotic production and resistance are ancient and widely distributed among microbes in the environment. This deep reservoir of resistance offers the opportunity for gene flow into susceptible disease-causing bacteria. Not all resistance genes are equally successfully mobilized, and some dominate in the clinic. The differences and similarities in resistance mechanisms and associated genes among environments reveal a complex interplay between gene capture and mobilization that requires study of gene diversity and gene product function to fully understand the breadth and depth of resistance and the risk to human health.201931330416
4322160.9998Multi-Drug Resistance in Bacterial Genomes-A Comprehensive Bioinformatic Analysis. Antimicrobial resistance is presently one of the greatest threats to public health. The excessive and indiscriminate use of antibiotics imposes a continuous selective pressure that triggers the emergence of multi-drug resistance. We performed a large-scale analysis of closed bacterial genomes to identify multi-drug resistance considering the ResFinder antimicrobial classes. We found that more than 95% of the genomes harbor genes associated with resistance to disinfectants, glycopeptides, macrolides, and tetracyclines. On average, each genome encodes resistance to more than nine different classes of antimicrobial drugs. We found higher-than-expected co-occurrences of resistance genes in both plasmids and chromosomes for several classes of antibiotic resistance, including classes categorized as critical according to the World Health Organization (WHO). As a result of antibiotic-resistant priority pathogens, higher-than-expected co-occurrences appear in plasmids, increasing the potential for resistance dissemination. For the first time, co-occurrences of antibiotic resistance have been investigated for priority pathogens as defined by the WHO. For critically important pathogens, co-occurrences appear in plasmids, not in chromosomes, suggesting that the resistances may be epidemic and probably recent. These results hint at the need for new approaches to treating infections caused by critically important bacteria.202337511196
3914170.9998Genomic Insights into Drug Resistance and Virulence Platforms, CRISPR-Cas Systems and Phylogeny of Commensal E. coli from Wildlife. Commensal bacteria act as important reservoirs of virulence and resistance genes. However, existing data are generally only focused on the analysis of human or human-related bacterial populations. There is a lack of genomic studies regarding commensal bacteria from hosts less exposed to antibiotics and other selective forces due to human activities, such as wildlife. In the present study, the genomes of thirty-eight E. coli strains from the gut of various wild animals were sequenced. The analysis of their accessory genome yielded a better understanding of the role of the mobilome on inter-bacterial dissemination of mosaic virulence and resistance plasmids. The study of the presence and composition of the CRISPR/Cas systems in E. coli from wild animals showed some viral and plasmid sequences among the spacers, as well as the relationship between CRISPR/Cas and E. coli phylogeny. Further, we constructed a single nucleotide polymorphisms-based core tree with E. coli strains from different sources (humans, livestock, food and extraintestinal environments). Bacteria from humans or highly human-influenced settings exhibit similar genetic patterns in CRISPR-Cas systems, plasmids or virulence/resistance genes-carrying modules. These observations, together with the absence of significant genetic changes in their core genome, suggest an ongoing flow of both mobile elements and E. coli lineages between human and natural ecosystems.202134063152
4148180.9998Plasmids in the environment. Bacterial plasmids existed in bacteria before the antibiotic era but their presence was brought into prominence by the use of antibiotics which selected for antibiotic resistant strains. Subsequently, the range of genes carried on plasmids was shown to extend far beyond those coding for antibiotic resistance. Any consideration of plasmids in the environment, therefore, must include all plasmids whether or not they are genetically linked with antibiotic resistance. Antibiotic resistant bacteria may be found in the environment either by contamination with excreta from man and animals in which the strains were selected, or by their selection within the environment by antibiotics synthesized in situ or reaching the environment in an undegraded form in sewage from man and animals, or from industry. Other agents, also contaminating the environment, exert a selective pressure such as heavy metals in industrial effluents which select for metal resistance. This paper reviews the incidences and role of plasmids in various habitats including natural waters, soil, pastures, farm wastes, and human sewage from both hospitalised and other populations. Aspects of plasmid ecology, their biological role, and the transmissibility of genetic material between bacteria within the environment are considered. Two recent studies in Bristol, UK, are reported. The first was a genetic study on Escherichia coli isolates from calf slurry. Various DNA probes were used to determine the extent of gene exchange between the various serotypes within the natural environment. The second was a preliminary study to determine the stability of a recombinant plasmid, in a wild strain of Escherichia coli of pig origin, after its release into a semi-contained farm situation. It is now recognized that plasmids are widely distributed in bacterial populations in terrestrial and aquatic environments. Many have been detected by their carriage of genes coding for antibiotic or heavy metal resistance. Others, mainly cryptic in nature, have been demonstrated by plasmid profile studies on isolates from various habitats. Plasmids were shown to be present in a relatively few bacteria deposited in culture collections prior to the antibiotic era. Subsequently, the increased prevalence of R plasmids in bacteria in most ecosystems were due mainly to the selective pressure imposed by the use of antibiotics. This pressure may have been exerted either in the environment in which the strains were found or elsewhere, the environment subsequently being contaminated by antibiotic resistant bacteria.(ABSTRACT TRUNCATED AT 400 WORDS)19883074480
4147190.9998Lack of evidence that DNA in antibiotic preparations is a source of antibiotic resistance genes in bacteria from animal or human sources. Although DNA encoding antibiotic resistance has been discovered in antibiotic preparations, its significance for the development of antibiotic resistance in bacteria is unknown. No phylogenetic evidence was obtained for recent horizontal transfer of antibiotic resistance genes from antibiotic-producing organisms to bacteria from human or animal sources.200415273135