# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 4128 | 0 | 0.9998 | Zinc and copper in animal feed - development of resistance and co-resistance to antimicrobial agents in bacteria of animal origin. Farmed animals such as pig and poultry receive additional Zn and Cu in their diets due to supplementing elements in compound feed as well as medical remedies. Enteral bacteria in farmed animals are shown to develop resistance to trace elements such as Zn and Cu. Resistance to Zn is often linked with resistance to methicillin in staphylococci, and Zn supplementation to animal feed may increase the proportion of multiresistant E. coli in the gut. Resistance to Cu in bacteria, in particular enterococci, is often associated with resistance to antimicrobial drugs like macrolides and glycopeptides (e.g. vancomycin). Such resistant bacteria may be transferred from the food-producing animals to humans (farmers, veterinarians, and consumers). Data on dose-response relation for Zn/Cu exposure and resistance are lacking; however, it seems more likely that a resistance-driven effect occurs at high trace element exposure than at more basal exposure levels. There is also lack of data which could demonstrate whether Zn/Cu-resistant bacteria may acquire antibiotic resistance genes/become antibiotics resistant, or if antibiotics-resistant bacteria are more capable to become Zn/Cu resistant than antibiotics-susceptible bacteria. Further research is needed to elucidate the link between Zn/Cu and antibiotic resistance in bacteria. | 2014 | 25317117 |
| 7705 | 1 | 0.9998 | Oxytetracycline reduces the diversity of tetracycline-resistance genes in the Galleria mellonella gut microbiome. BACKGROUND: Clinically-relevant multidrug resistance is sometimes present in bacteria not exposed to human-made antibiotics, in environments without extreme selective pressures, such as the insect gut. The use of antibiotics on naïve microbiomes often leads to decreased microbe diversity and increased antibiotic resistance. RESULTS: Here we investigate the impact of antibiotics on the insect gut microbiome by identifying tetracycline-resistance genes in the gut bacteria of greater wax moth (Galleria mellonella) larvae, feeding on artificial food containing oxytetracycline. We determined that G. mellonella can be raised on artificial food for over five generations and that the insects tolerate low doses of antibiotics in their diets, but doses of oxytetracycline higher than sub-inhibitory lead to early larval mortality. In our experiments, greater wax moth larvae had a sparse microbiome, which is consistent with previous findings. Additionally, we determined that the microbiome of G. mellonella larvae not exposed to antibiotics carries a number of tetracycline-resistance genes and some of that diversity is lost upon exposure to strong selective pressure. CONCLUSIONS: We show that G. mellonella larvae can be raised on artificial food, including antibiotics, for several generations and that the microbiome can be sampled. We show that, in the absence of antibiotics, the insect gut microbiome can maintain a diverse pool of tetracycline-resistance genes. Selective pressure, from exposure to the antibiotic oxytetracycline, leads to microbiome changes and alteration in the tetracycline-resistance gene pool. | 2018 | 30594143 |
| 4129 | 2 | 0.9998 | Residential Bacteria on Surfaces in the Food Industry and Their Implications for Food Safety and Quality. Surface hygiene is commonly measured as a part of the quality system of food processing plants, but as the bacteria present are commonly not identified, their roles for food quality and safety are not known. Here, we review the identity of residential bacteria and characteristics relevant for survival and growth in the food industry along with potential implications for food safety and quality. Sampling after cleaning and disinfection increases the likelihood of targeting residential bacteria. The increasing use of sequencing technologies to identify bacteria has improved knowledge about the bacteria present in food premises. Overall, nonpathogenic Gram-negative bacteria, especially Pseudomonas spp., followed by Enterobacteriaceae and Acinetobacter spp. dominate on food processing surfaces. Pseudomonas spp. persistence is likely due to growth at low temperatures, biofilm formation, tolerance to biocides, and low growth requirements. Gram-positive bacteria are most frequently found in dairies and in dry production environments. The residential bacteria may end up in the final products through cross-contamination and may affect food quality. Such effects can be negative and lead to spoilage, but the bacteria may also contribute positively, as through spontaneous fermentation. Pathogenic bacteria present in food processing environments may interact with residential bacteria, resulting in both inhibitory and stimulatory effects on pathogens in multispecies biofilms. The residential bacterial population, or bacteriota, does not seem to be an important source for the transfer of antibiotic resistance genes to humans, but more knowledge is needed to verify this. If residential bacteria occur in high numbers, they may influence processes such as membrane filtration and corrosion. | 2017 | 33371605 |
| 3800 | 3 | 0.9998 | Alterations of Salmonella enterica Serovar Typhimurium Antibiotic Resistance under Environmental Pressure. Microbial horizontal gene transfer is a continuous process that shapes bacterial genomic adaptation to the environment and the composition of concurrent microbial ecology. This includes the potential impact of synthetic antibiotic utilization in farm animal production on overall antibiotic resistance issues; however, the mechanisms behind the evolution of microbial communities are not fully understood. We explored potential mechanisms by experimentally examining the relatedness of phylogenetic inference between multidrug-resistant Salmonella enterica serovar Typhimurium isolates and pathogenic Salmonella Typhimurium strains based on genome-wide single-nucleotide polymorphism (SNP) comparisons. Antibiotic-resistant S Typhimurium isolates in a simulated farm environment barely lost their resistance, whereas sensitive S Typhimurium isolates in soils gradually acquired higher tetracycline resistance under antibiotic pressure and manipulated differential expression of antibiotic-resistant genes. The expeditious development of antibiotic resistance and the ensuing genetic alterations in antimicrobial resistance genes in S Typhimurium warrant effective actions to control the dissemination of Salmonella antibiotic resistance.IMPORTANCE Antibiotic resistance is attributed to the misuse or overuse of antibiotics in agriculture, and antibiotic resistance genes can also be transferred to bacteria under environmental stress. In this study, we report a unidirectional alteration in antibiotic resistance from susceptibility to increased resistance. Highly sensitive Salmonella enterica serovar Typhimurium isolates from organic farm systems quickly acquired tetracycline resistance under antibiotic pressure in simulated farm soil environments within 2 weeks, with expression of antibiotic resistance-related genes that was significantly upregulated. Conversely, originally resistant S Typhimurium isolates from conventional farm systems lost little of their resistance when transferred to environments without antibiotic pressure. Additionally, multidrug-resistant S Typhimurium isolates genetically shared relevancy with pathogenic S Typhimurium isolates, whereas susceptible isolates clustered with nonpathogenic strains. These results provide detailed discussion and explanation about the genetic alterations and simultaneous acquisition of antibiotic resistance in S Typhimurium in agricultural environments. | 2018 | 30054356 |
| 4127 | 4 | 0.9998 | The 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. | 2021 | 34065307 |
| 7693 | 5 | 0.9998 | Prevalence of Antibiotic Resistance Genes among Human Gut-Derived Bifidobacteria. The microbiota of the human gastrointestinal tract (GIT) may regularly be exposed to antibiotics, which are used to prevent and treat infectious diseases caused by bacteria and fungi. Bacterial communities of the gut retain a reservoir of antibiotic resistance (AR) genes, and antibiotic therapy thus positively selects for those microorganisms that harbor such genetic features, causing microbiota modulation. During the first months following birth, bifidobacteria represent some of the most dominant components of the human gut microbiota, although little is known about their AR gene complement (or resistome). In the current study, we assessed the resistome of the Bifidobacterium genus based on phenotypic and genotypic data of members that represent all currently recognized bifidobacterial (sub)species. Moreover, a comparison between the bifidobacterial resistome and gut metagenome data sets from adults and infants shows that the bifidobacterial community present at the first week following birth possesses a reduced AR arsenal compared to that present in the infant bifidobacterial population in subsequent weeks of the first year of life. Our findings reinforce the concept that the early infant gut microbiota is more susceptible to disturbances by antibiotic treatment than the gut microbiota developed at a later life stage. IMPORTANCE: The spread of resistance to antibiotics among bacterial communities has represented a major concern since their discovery in the last century. The risk of genetic transfer of resistance genes between microorganisms has been extensively investigated due to its relevance to human health. In contrast, there is only limited information available on antibiotic resistance among human gut commensal microorganisms such as bifidobacteria, which are widely exploited by the food industry as health-promoting microorganisms or probiotic ingredients. In the current study, we explored the occurrence of antibiotic resistance genes in the genomes of bifidobacteria and evaluated their genetic mobility to other human gut commensal microorganisms. | 2017 | 27864179 |
| 3830 | 6 | 0.9998 | Resistance Gene Carriage Predicts Growth of Natural and Clinical Escherichia coli Isolates in the Absence of Antibiotics. Bacterial pathogens that carry antibiotic resistance alleles sometimes pay a cost in the form of impaired growth in antibiotic-free conditions. This cost of resistance is expected to be a key parameter for understanding how resistance spreads and persists in pathogen populations. Analysis of individual resistance alleles from laboratory evolution and natural isolates has shown they are typically costly, but these costs are highly variable and influenced by genetic variation at other loci. It therefore remains unclear how strongly resistance is linked to impaired antibiotic-free growth in bacteria from natural and clinical scenarios, where resistance alleles are likely to coincide with other types of genetic variation. To investigate this, we measured the growth of 92 natural and clinical Escherichia coli isolates across three antibiotic-free environments. We then tested whether variation of antibiotic-free growth among isolates was predicted by their resistance to 10 antibiotics, while accounting for the phylogenetic structure of the data. We found that isolates with similar resistance profiles had similar antibiotic-free growth profiles, but it was not simply that higher average resistance was associated with impaired growth. Next, we used whole-genome sequences to identify antibiotic resistance genes and found that isolates carrying a greater number of resistance gene types grew relatively poorly in antibiotic-free conditions, even when the resistance genes they carried were different. This suggests that the resistance of bacterial pathogens is linked to growth costs in nature, but it is the total genetic burden and multivariate resistance phenotype that predict these costs, rather than individual alleles or mean resistance across antibiotics.IMPORTANCE Managing the spread of antibiotic resistance in bacterial pathogens is a major challenge for global public health. Central to this challenge is understanding whether resistance is linked to impaired bacterial growth in the absence of antibiotics, because this determines whether resistance declines when bacteria are no longer exposed to antibiotics. We studied 92 isolates of the key bacterial pathogen Escherichia coli; these isolates varied in both their antibiotic resistance genes and other parts of the genome. Taking this approach, rather than focusing on individual genetic changes associated with resistance as in much previous work, revealed that growth without antibiotics was linked to the number of specialized resistance genes carried and the combination of antibiotics to which isolates were resistant but was not linked to average antibiotic resistance. This approach provides new insights into the genetic factors driving the long-term persistence of antibiotic-resistant bacteria, which is important for future efforts to predict and manage resistance. | 2019 | 30530714 |
| 3905 | 7 | 0.9997 | Recent Genetic Changes Affecting Enterohemorrhagic Escherichia coli Causing Recurrent Outbreaks. Enterohemorrhagic E. coli (EHEC) is responsible for significant human illness, death, and economic loss. The main reservoir for EHEC is cattle, but plant-based foods are common vectors for human infection. Several outbreaks have been attributed to lettuce and leafy green vegetables grown in the Salinas and Santa Maria regions of California. Bacteria causing different outbreaks are mostly not close relatives, but one group of closely-related O157:H7 has caused several of them. This unusual pattern of recurrence may have some genetic basis. Here I use whole-genome sequences to reconstruct the genetic changes that occurred in the recent ancestry of this EHEC. In a short period of time corresponding to little genetic change, there were several changes to adhesion-related sequences, mainly adhesins. These changes may have greatly altered the adhesive properties of the bacteria. Possible consequences include increased persistence of cattle infections, more bacteria shed in cattle feces, and greater virulence in humans. Similar constellations of genetic change, which are detectable by current sequencing-based surveillance, may identify other bacteria that are particular threats to human health. In addition, the Santa Maria subclade carries a nonsense mutation affecting ArsR, a repressor of genes that confer resistance to arsenic and antimony. This suggests that the persistent source of Santa Maria contamination is located in an area with arsenic-contaminated groundwater, a problem in many parts of California. This inference may aid identification of the reservoir of EHEC, which would greatly aid mitigation efforts. IMPORTANCE Food-borne bacterial infections cause substantial illness and death. Understanding how bacteria contaminate food and cause disease is important for combating the problem. Closely-related E. coli, likely originating in cattle, have repeatedly caused outbreaks spread by vegetables grown in California. Such recurrence is atypical, and might have a genetic basis. The genetic changes that occurred in the recent ancestry of these E. coli can be reconstructed from their DNA sequences. Several mutations affect genes involved in bacterial adhesion. These might affect persistence of infection in cattle, quantity of bacteria in their feces, and human disease. They also suggest a way of detecting dangerous bacteria from their genome sequences. Furthermore, a subgroup carries a mutation affecting the regulation of genes conferring arsenic resistance. This suggests that the reservoir for contamination utilizes groundwater contaminated with arsenic, a problem in parts of California. This observation may be an aid to locating the persistent reservoir of contamination. | 2022 | 35467376 |
| 9629 | 8 | 0.9997 | Costs of antibiotic resistance genes depend on host strain and environment and can influence community composition. Antibiotic resistance genes (ARGs) benefit host bacteria in environments containing corresponding antibiotics, but it is less clear how they are maintained in environments where antibiotic selection is weak or sporadic. In particular, few studies have measured if the direct effect of ARGs on host fitness is fixed or if it depends on the host strain, perhaps marking some ARG-host combinations as selective refuges that can maintain ARGs in the absence of antibiotic selection. We quantified the fitness effects of six ARGs in 11 diverse Escherichia spp. strains. Three ARGs (bla(TEM-116), cat and dfrA5, encoding resistance to β-lactams, chloramphenicol, and trimethoprim, respectively) imposed an overall cost, but all ARGs had an effect in at least one host strain, reflecting a significant strain interaction effect. A simulation predicts these interactions can cause the success of ARGs to depend on available host strains, and, to a lesser extent, can cause host strain success to depend on the ARGs present in a community. These results indicate the importance of considering ARG effects across different host strains, and especially the potential of refuge strains to allow resistance to persist in the absence of direct selection, in efforts to understand resistance dynamics. | 2024 | 38889784 |
| 3826 | 9 | 0.9997 | Co-resistance: an opportunity for the bacteria and resistance genes. Co-resistance involves transfer of several genes into the same bacteria and/or the acquisition of mutations in different genetic loci affecting different antimicrobials whereas pleiotropic resistance implies the same genetic event affecting several antimicrobials. There is an increasing prevalence of isolates with co-resistance which are over-represented within the so-called high-risk clones. Compensatory events avoid fitness cost of co-resistance, even in the absence of antimicrobials. Nevertheless, they might be selected by different antimicrobials and a single agent might select co-resistant isolates. This process, named as co-selection, is not avoided with cycling or mixing strategies of antimicrobial use. Co-resistance and co-selection processes increase the opportunity for persistence of the bacteria and resistance genes and should be considered when designing strategies for decreasing antimicrobial resistance. | 2011 | 21840259 |
| 3882 | 10 | 0.9997 | Clusters of Antibiotic Resistance Genes Enriched Together Stay Together in Swine Agriculture. Antibiotic resistance is a worldwide health risk, but the influence of animal agriculture on the genetic context and enrichment of individual antibiotic resistance alleles remains unclear. Using quantitative PCR followed by amplicon sequencing, we quantified and sequenced 44 genes related to antibiotic resistance, mobile genetic elements, and bacterial phylogeny in microbiomes from U.S. laboratory swine and from swine farms from three Chinese regions. We identified highly abundant resistance clusters: groups of resistance and mobile genetic element alleles that cooccur. For example, the abundance of genes conferring resistance to six classes of antibiotics together with class 1 integrase and the abundance of IS6100-type transposons in three Chinese regions are directly correlated. These resistance cluster genes likely colocalize in microbial genomes in the farms. Resistance cluster alleles were dramatically enriched (up to 1 to 10% as abundant as 16S rRNA) and indicate that multidrug-resistant bacteria are likely the norm rather than an exception in these communities. This enrichment largely occurred independently of phylogenetic composition; thus, resistance clusters are likely present in many bacterial taxa. Furthermore, resistance clusters contain resistance genes that confer resistance to antibiotics independently of their particular use on the farms. Selection for these clusters is likely due to the use of only a subset of the broad range of chemicals to which the clusters confer resistance. The scale of animal agriculture and its wastes, the enrichment and horizontal gene transfer potential of the clusters, and the vicinity of large human populations suggest that managing this resistance reservoir is important for minimizing human risk. IMPORTANCE: Agricultural antibiotic use results in clusters of cooccurring resistance genes that together confer resistance to multiple antibiotics. The use of a single antibiotic could select for an entire suite of resistance genes if they are genetically linked. No links to bacterial membership were observed for these clusters of resistance genes. These findings urge deeper understanding of colocalization of resistance genes and mobile genetic elements in resistance islands and their distribution throughout antibiotic-exposed microbiomes. As governments seek to combat the rise in antibiotic resistance, a balance is sought between ensuring proper animal health and welfare and preserving medically important antibiotics for therapeutic use. Metagenomic and genomic monitoring will be critical to determine if resistance genes can be reduced in animal microbiomes, or if these gene clusters will continue to be coselected by antibiotics not deemed medically important for human health but used for growth promotion or by medically important antibiotics used therapeutically. | 2016 | 27073098 |
| 3997 | 11 | 0.9997 | Pyrosequencing of antibiotic-contaminated river sediments reveals high levels of resistance and gene transfer elements. The high and sometimes inappropriate use of antibiotics has accelerated the development of antibiotic resistance, creating a major challenge for the sustainable treatment of infections world-wide. Bacterial communities often respond to antibiotic selection pressure by acquiring resistance genes, i.e. mobile genetic elements that can be shared horizontally between species. Environmental microbial communities maintain diverse collections of resistance genes, which can be mobilized into pathogenic bacteria. Recently, exceptional environmental releases of antibiotics have been documented, but the effects on the promotion of resistance genes and the potential for horizontal gene transfer have yet received limited attention. In this study, we have used culture-independent shotgun metagenomics to investigate microbial communities in river sediments exposed to waste water from the production of antibiotics in India. Our analysis identified very high levels of several classes of resistance genes as well as elements for horizontal gene transfer, including integrons, transposons and plasmids. In addition, two abundant previously uncharacterized resistance plasmids were identified. The results suggest that antibiotic contamination plays a role in the promotion of resistance genes and their mobilization from environmental microbes to other species and eventually to human pathogens. The entire life-cycle of antibiotic substances, both before, under and after usage, should therefore be considered to fully evaluate their role in the promotion of resistance. | 2011 | 21359229 |
| 4051 | 12 | 0.9997 | The human microbiome harbors a diverse reservoir of antibiotic resistance genes. The increasing levels of multi-drug resistance in human pathogenic bacteria are compromising our ability to treat infectious disease. Since antibiotic resistance determinants are readily exchanged between bacteria through lateral gene transfer, there is an increasing interest in investigating reservoirs of antibiotic resistance accessible to pathogens. Due to the high likelihood of contact and genetic exchange with pathogens during disease progression, the human microflora warrants special attention as perhaps the most accessible reservoir of resistance genes. Indeed, numerous previous studies have demonstrated substantial antibiotic resistance in cultured isolates from the human microflora. By applying metagenomic functional selections, we recently demonstrated that the functional repertoire of resistance genes in the human microbiome is much more diverse than suggested using previous culture-dependent methods. We showed that many resistance genes from cultured proteobacteria from human fecal samples are identical to resistance genes harbored by human pathogens, providing strong support for recent genetic exchange of this resistance machinery. In contrast, most of the resistance genes we identified with culture independent metagenomic sampling from the same samples were novel when compared to all known genes in public databases. While this clearly demonstrates that the antibiotic resistance reservoir of the large fraction of the human microbiome recalcitrant to culturing is severely under sampled, it may also suggest that barriers exist to lateral gene transfer between these bacteria and readily cultured human pathogens. If we hope to turn the tide against multidrug resistant infections, we must urgently commit to quantitatively characterizing the resistance reservoirs encoded by our diverse human microbiomes, with a particular focus on routes of exchange of these reservoirs with other microbial communities. | 2010 | 21178459 |
| 4651 | 13 | 0.9997 | Long-term shifts in patterns of antibiotic resistance in enteric bacteria. Several mechanisms are responsible for the ability of microorganisms to tolerate antibiotics, and the incidence of resistance to these compounds within bacterial species has increased since the commercial use of antibiotics became widespread. To establish the extent of and changes in the diversity of antibiotic resistance patterns in natural populations, we determined the MICs of five antibiotics for collections of enteric bacteria isolated from diverse hosts and geographic locations and during periods before and after commercial application of antibiotics began. All of the pre-antibiotic era strains were susceptible to high levels of these antibiotics, whereas 20% of strains from contemporary populations of Escherichia coli and Salmonella enterica displayed high-level resistance to at least one of the antibiotics. In addition to the increase in the frequency of high-level resistance, background levels, conferred by genes providing nonspecific low-level resistance to multiple antibiotics, were significantly higher among contemporary strains. Changes in the incidence and levels of antibiotic resistance are not confined to particular segments of the bacterial population and reflect responses to the increased exposure of bacteria to antimicrobial compounds over the past several decades. | 2000 | 11097921 |
| 3884 | 14 | 0.9997 | Distribution 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. | 2012 | 23133629 |
| 9258 | 15 | 0.9997 | Plasmid Viability Depends on the Ecological Setting of Hosts within a Multiplasmid Community. Plasmids are extrachromosomal genetic elements, some of which disperse horizontally between different strains and species of bacteria. They are a major factor in the dissemination of virulence factors and antibiotic resistance. Understanding the ecology of plasmids has a notable anthropocentric value, and therefore, the interactions between bacterial hosts and individual plasmids have been studied in detail. However, bacterial systems often carry multiple genetically distinct plasmids, but dynamics within these multiplasmid communities have remained unstudied. Here, we set to investigate the survival of 11 mobilizable or conjugative plasmids under five different conditions where the hosts had a differing ecological status in comparison to other bacteria in the system. The key incentive was to determine whether plasmid dynamics are reproducible and whether there are tradeoffs in plasmid fitness that stem from the ecological situation of their initial hosts. Growth rates and maximum population densities increased in all communities and treatments over the 42-day evolution experiment, although plasmid contents at the end varied notably. Large multiresistance-conferring plasmids were unfit when the community also contained smaller plasmids with fewer resistance genes. This suggests that restraining the use of a few antibiotics can make bacterial communities sensitive to others. In general, the presence or absence of antibiotic selection and plasmid-free hosts (of various fitnesses) has a notable influence on which plasmids survive. These tradeoffs in different settings can help explain, for example, why some resistance plasmids have an advantage during a rapid proliferation of antibiotic-sensitive pathogens whereas others dominate in alternative situations. IMPORTANCE Conjugative and mobilizable plasmids are ubiquitous in bacterial systems. Several different plasmids can compete within a single bacterial community. We here show that the ecological setting of the host bacteria has a notable effect on the survival of individual plasmids. Selection for opportunistic genes such as antibiotic resistance genes and the presence of plasmid-free hosts can determine which plasmids survive in the system. Host bacteria appear to adapt specifically to a situation where there are multiple plasmids present instead of alleviating the plasmid-associated fitness costs of individual plasmids. Plasmids providing antibiotic resistance survived under all conditions even if there was a constant migration of higher-fitness plasmid-free hosts and no selection via antibiotics. This study is one of the first to observe the behavior of multiple genetically different plasmids as a part of a single system. | 2022 | 35416702 |
| 4126 | 16 | 0.9997 | The Impact of Non-Pathogenic Bacteria on the Spread of Virulence and Resistance Genes. This review discusses the fate of antimicrobial resistance and virulence genes frequently present among microbiomes. A central concept in epidemiology is the mean number of hosts colonized by one infected host in a population of susceptible hosts: R(0). It characterizes the disease's epidemic potential because the pathogen continues its propagation through susceptible hosts if it is above one. R(0) is proportional to the average duration of infections, but non-pathogenic microorganisms do not cause host death, and hosts do not need to be rid of them. Therefore, commensal bacteria may colonize hosts for prolonged periods, including those harboring drug resistance or even a few virulence genes. Thus, their R(0) is likely to be (much) greater than one, with peculiar consequences for the spread of virulence and resistance genes. For example, computer models that simulate the spread of these genes have shown that their diversities should correlate positively throughout microbiomes. Bioinformatics analysis with real data corroborates this expectation. Those simulations also anticipate that, contrary to the common wisdom, human's microbiomes with a higher diversity of both gene types are the ones that took antibiotics longer ago rather than recently. Here, we discuss the mechanisms and robustness behind these predictions and other public health consequences. | 2023 | 36768286 |
| 4054 | 17 | 0.9997 | Ecological impact of antibiotic use in animals on different complex microflora: environment. Different means of interaction between microecological systems in different animal hosts (including humans) and the environment may occur during the transfer of resistant bacteria and their resistance genes. Spread of resistance takes place in different ways with respect to clonal spread of resistance strains by the spread of wide host range plasmids and translocatable elements. Commensals in ecosystems have a special significance and a pronounced capacity for acquisition and transfer of resistance genes as with Enterococcus faecium and Escherichia coli in the gut flora or Pseudomonas spp. in aquatic environments. The route of transmission from animals to humans by meat products is well established. Other routes via water and food plants (vegetables) have been investigated less, although resistance genes transfer in aquatic environments as evidenced from sequence comparison of such genes (e.g. tetR, floR in Salmonella typhimurium DT104). Whether this is due to rare but important transfer events or whether there is a more frequent exchange in aquatic or terrestrial environments needs further elucidation. | 2000 | 10794954 |
| 3971 | 18 | 0.9997 | Monitoring and identifying antibiotic resistance mechanisms in bacteria. Sub-therapeutic administration of antibiotics to animals is under intense scrutiny because they contribute to the dissemination of antibiotic-resistant bacteria into the food chain. Studies suggest that there is a link between the agricultural use of antibiotics and antibiotic-resistant human infections. Antibiotic-resistant organisms from animal and human wastes reenter the human and animal populations through a number of pathways including natural waters, irrigation water, drinking water, and vegetables and foods. Antibiotic usage in the United States for animal production (disease prevention and growth promotion) is estimated to be 18 million pounds annually. As much as 25 to 75% of the antibiotics administered to feedlot animals are excreted unaltered in feces. Because about 180 million dry tons of livestock and poultry waste is generated annually in the United States, it is not surprising that animal-derived antibiotic-resistant organisms are found contaminating groundwater, surface water, and food crops. It is extremely important to clearly understand the molecular mechanisms that could potentially cause lateral or horizontal gene transfer of antibiotic resistance genes among bacteria. Once the mechanisms and magnitude of resistance gene transfer are clearly understood and quantified, strategies can be instituted to reduce the potential for dissemination of these genes. | 2003 | 12710483 |
| 4228 | 19 | 0.9997 | Resistance to antibiotics in the normal flora of animals. The normal bacterial flora contains antibiotic resistance genes to various degrees, even in individuals with no history of exposure to commercially prepared antibiotics. Several factors seem to increase the number of antibiotic-resistant bacteria in feces. One important factor is the exposure of the intestinal flora to antibacterial drugs. Antibiotics used as feed additives seem to play an important role in the development of antibiotic resistance in normal flora bacteria. The use of avoparcin as a feed additive has demonstrated that an antibiotic considered "safe" is responsible for increased levels of antibiotic resistance in the normal flora enterococci of animals fed with avoparcin and possibly in humans consuming products from these animals. However, other factors like stress from temperature, crowding, and management also seem to contribute to the occurrence of antibiotic resistance in normal flora bacteria. The normal flora of animals has been studied with respect to the development of antibiotic resistance over four decades, but there are few studies with the intestinal flora as the main focus. The results of earlier studies are valuable when focused against the recent understanding of mobile genetics responsible for bacterial antibiotic resistance. New studies should be undertaken to assess whether the development of antibiotic resistance in the normal flora is directly linked to the dramatic increase in antibiotic resistance of bacterial pathogens. Bacteria of the normal flora, often disregarded scientifically, should be studied with the intention of using them as active protection against infectious diseases and thereby contributing to the overall reduction of use of antibioties in both animals and humans. | 2001 | 11432415 |