# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 4041 | 0 | 1.0000 | The human gut resistome. In recent decades, the emergence and spread of antibiotic resistance among bacterial pathogens has become a major threat to public health. Bacteria can acquire antibiotic resistance genes by the mobilization and transfer of resistance genes from a donor strain. The human gut contains a densely populated microbial ecosystem, termed the gut microbiota, which offers ample opportunities for the horizontal transfer of genetic material, including antibiotic resistance genes. Recent technological advances allow microbiota-wide studies into the diversity and dynamics of the antibiotic resistance genes that are harboured by the gut microbiota ('the gut resistome'). Genes conferring resistance to antibiotics are ubiquitously present among the gut microbiota of humans and most resistance genes are harboured by strictly anaerobic gut commensals. The horizontal transfer of genetic material, including antibiotic resistance genes, through conjugation and transduction is a frequent event in the gut microbiota, but mostly involves non-pathogenic gut commensals as these dominate the microbiota of healthy individuals. Resistance gene transfer from commensals to gut-dwelling opportunistic pathogens appears to be a relatively rare event but may contribute to the emergence of multi-drug resistant strains, as is illustrated by the vancomycin resistance determinants that are shared by anaerobic gut commensals and the nosocomial pathogen Enterococcus faecium. | 2015 | 25918444 |
| 4040 | 1 | 0.9999 | Molecular Insights into Antimicrobial Resistance Traits of Commensal Human Gut Microbiota. Antimicrobial resistance (AMR) among bacterial species that resides in complex ecosystems is a natural phenomenon. Indiscriminate use of antimicrobials in healthcare, livestock, and agriculture provides an evolutionary advantage to the resistant variants to dominate the ecosystem. Ascendency of resistant variants threatens the efficacy of most, if not all, of the antimicrobial drugs commonly used to prevent and/or cure microbial infections. Resistant phenotype is very common in enteric bacteria. The most common mechanisms of AMR are enzymatic modifications to the antimicrobials or their target molecules. In enteric bacteria, most of the resistance traits are acquired by horizontal gene transfer from closely or distantly related bacterial population. AMR traits are generally linked with mobile genetic elements (MGEs) and could rapidly disseminate to the bacterial species through horizontal gene transfer (HGT) from a pool of resistance genes. Although prevalence of AMR genes among pathogenic bacteria is widely studied in the interest of infectious disease management, the resistance profile and the genetic traits that encode resistance to the commensal microbiota residing in the gut of healthy humans are not well-studied. In the present study, we have characterized AMR phenotypes and genotypes of five dominant commensal enteric bacteria isolated from the gut of healthy Indians. Our study revealed that like pathogenic bacteria, enteric commensals are also multidrug-resistant. The genes encoding antibiotic resistance are physically linked with MGEs and could disseminate vertically to the progeny and laterally to the distantly related microbial species. Consequently, the AMR genes present in the chromosome of commensal gut bacteria could be a potential source of resistance functions for other enteric pathogens. | 2019 | 30009332 |
| 4042 | 2 | 0.9999 | Integrons in the intestinal microbiota as reservoirs for transmission of antibiotic resistance genes. The human intestinal microbiota plays a major beneficial role in immune development and resistance to pathogens. The use of antibiotics, however, can cause the spread of antibiotic resistance genes within the resident intestinal microbiota. Important vectors for this are integrons. This review therefore focuses on the integrons in non-pathogenic bacteria as a potential source for the development and persistence of multidrug resistance. Integrons are a group of genetic elements which are assembly platforms that can capture specific gene cassettes and express them. Integrons in pathogenic bacteria have been extensively investigated, while integrons in the intestinal microbiota have not yet gained much attention. Knowledge of the integrons residing in the microbiota, however, can potentially aid in controlling the spread of antibiotic resistance genes to pathogens. | 2014 | 25437798 |
| 4024 | 3 | 0.9999 | Potential influence of antimicrobial resistance gene content in probiotic bacteria on the gut resistome ecosystems. Antimicrobial resistance (AMR) poses a substantial threat to human health. The commensal bacteria of the gut microbiome were shown to serve as a reservoir of antibiotic resistance genes (ARGs), termed the gut resistome, which has the potential to transfer horizontally to pathogens and contribute to the emergence of drug-resistant bacteria. Namely, AMR traits are generally linked with mobile genetic elements (MGEs), which apart from disseminating vertically to the progeny, may cross horizontally to the distantly related microbial species. On the other hand, while probiotics are generally considered beneficiary to human health, and are therefore widely consumed in recent years most commonly in conjunction with antibiotics, the complexities and extent of their impact on the gut microbiome and resistome have not been elucidated. By reviewing the latest studies on ARG containing commercial probiotic products and common probiotic supplement species with their actual effects on the human gut resistome, this study aims to demonstrate that their contribution to the spread of ARGs along the GI tract merits additional attention, but also indicates the changes in sampling and profiling of the gut microbiome which may allow for the more comprehensive studying of the effects of probiotics in this part of the resistome. | 2023 | 36819705 |
| 4027 | 4 | 0.9999 | Good microbes, bad genes? The dissemination of antimicrobial resistance in the human microbiome. A global rise in antimicrobial resistance among pathogenic bacteria has proved to be a major public health threat, with the rate of multidrug-resistant bacterial infections increasing over time. The gut microbiome has been studied as a reservoir of antibiotic resistance genes (ARGs) that can be transferred to bacterial pathogens via horizontal gene transfer (HGT) of conjugative plasmids and mobile genetic elements (the gut resistome). Advances in metagenomic sequencing have facilitated the identification of resistome modulators, including live microbial therapeutics such as probiotics and fecal microbiome transplantation that can either expand or reduce the abundances of ARG-carrying bacteria in the gut. While many different gut microbes encode for ARGs, they are not uniformly distributed across, or transmitted by, various members of the microbiome, and not all are of equal clinical relevance. Both experimental and theoretical approaches in microbial ecology have been applied to understand differing frequencies of ARG horizontal transfer between commensal microbes as well as between commensals and pathogens. In this commentary, we assess the evidence for the role of commensal gut microbes in encoding antimicrobial resistance genes, the degree to which they are shared both with other commensals and with pathogens, and the host and environmental factors that can impact resistome dynamics. We further discuss novel sequencing-based approaches for identifying ARGs and predicting future transfer events of clinically relevant ARGs from commensals to pathogens. | 2022 | 35332832 |
| 4051 | 5 | 0.9999 | 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 |
| 4054 | 6 | 0.9999 | 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 |
| 4048 | 7 | 0.9999 | Mobile genetic elements in the genus Bacteroides, and their mechanism(s) of dissemination. Bacteroides spp organisms, the predominant commensal bacteria in the human gut have become increasingly resistant to many antibiotics. They are now also considered to be reservoirs of antibiotic resistance genes due to their capacity to harbor and disseminate these genes via mobile transmissible elements that occur in bewildering variety. Gene dissemination occurs within and from Bacteroides spp primarily by conjugation, the molecular mechanisms of which are still poorly understood in the genus, even though the need to prevent this dissemination is urgent. One current avenue of research is thus focused on interventions that use non-antibiotic methodologies to prevent conjugation-based DNA transfer. | 2011 | 22479685 |
| 4025 | 8 | 0.9999 | Metagenomic Insights into Transferable Antibiotic Resistance in Oral Bacteria. Antibiotic resistance is considered one of the greatest threats to global public health. Resistance is often conferred by the presence of antibiotic resistance genes (ARGs), which are readily found in the oral microbiome. In-depth genetic analyses of the oral microbiome through metagenomic techniques reveal a broad distribution of ARGs (including novel ARGs) in individuals not recently exposed to antibiotics, including humans in isolated indigenous populations. This has resulted in a paradigm shift from focusing on the carriage of antibiotic resistance in pathogenic bacteria to a broader concept of an oral resistome, which includes all resistance genes in the microbiome. Metagenomics is beginning to demonstrate the role of the oral resistome and horizontal gene transfer within and between commensals in the absence of selective pressure, such as an antibiotic. At the chairside, metagenomic data reinforce our need to adhere to current antibiotic guidelines to minimize the spread of resistance, as such data reveal the extent of ARGs without exposure to antimicrobials and the ecologic changes created in the oral microbiome by even a single dose of antibiotics. The aim of this review is to discuss the role of metagenomics in the investigation of the oral resistome, including the transmission of antibiotic resistance in the oral microbiome. Future perspectives, including clinical implications of the findings from metagenomic investigations of oral ARGs, are also considered. | 2016 | 27183895 |
| 4028 | 9 | 0.9999 | Horizontal transfer of antibiotic resistance genes in the human gut microbiome. Infections caused by antibiotic-resistant bacteria are a major threat to public health. The pathogens causing these infections can acquire antibiotic resistance genes in a process termed horizontal gene transfer (HGT). HGT is a common event in the human gut microbiome, that is, the microbial ecosystem of the human intestinal tract. HGT in the gut microbiome can occur via different mechanisms of which transduction and conjugation have been best characterised. Novel bioinformatic tools and experimental approaches have been developed to determine the association of antibiotic resistance genes with their microbial hosts and to quantify the extent of HGT in the gut microbiome. Insights from studies into HGT in the gut microbiome may lead to the development of novel interventions to minimise the spread of antibiotic resistance genes among commensals and opportunistic pathogens. | 2020 | 32143027 |
| 7693 | 10 | 0.9999 | 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 |
| 9652 | 11 | 0.9999 | Transfer and Persistence of a Multi-Drug Resistance Plasmid in situ of the Infant Gut Microbiota in the Absence of Antibiotic Treatment. The microbial ecosystem residing in the human gut is believed to play an important role in horizontal exchange of virulence and antibiotic resistance genes that threatens human health. While the diversity of gut-microorganisms and their genetic content has been studied extensively, high-resolution insight into the plasticity, and selective forces shaping individual genomes is scarce. In a longitudinal study, we followed the dynamics of co-existing Escherichia coli lineages in an infant not receiving antibiotics. Using whole genome sequencing, we observed large genomic deletions, bacteriophage infections, as well as the loss and acquisition of plasmids in these lineages during their colonization of the human gut. In particular, we captured the exchange of multidrug resistance genes, and identified a clinically relevant conjugative plasmid mediating the transfer. This resistant transconjugant lineage was maintained for months, demonstrating that antibiotic resistance genes can disseminate and persist in the gut microbiome; even in absence of antibiotic selection. Furthermore, through in vivo competition assays, we suggest that the resistant transconjugant can persist through a fitness advantage in the mouse gut in spite of a fitness cost in vitro. Our findings highlight the dynamic nature of the human gut microbiota and provide the first genomic description of antibiotic resistance gene transfer between bacteria in the unperturbed human gut. These results exemplify that conjugative plasmids, harboring resistance determinants, can transfer and persists in the gut in the absence of antibiotic treatment. | 2017 | 29018426 |
| 4044 | 12 | 0.9999 | Antibiotic resistance in food-related bacteria--a result of interfering with the global web of bacterial genetics. A series of antibiotic resistance genes have been sequenced and found to be identical or nearly identical in various ecological environments. Similarly, genetic vectors responsible for assembly and mobility of antibiotic resistance genes, such as transposons, integrons and R plasmids of similar or identical type are also widespread in various niches of the environment. Many zoonotic bacteria carry antibiotic resistance genes directly from different food-producing environments to the human being. These circumstances may have a major impact on the degree for success in treating infectious diseases in man. Several recent examples demonstrate that use of antibiotics in all parts of the food production chain contributes to the increasing level of antibiotic resistance among the food-borne pathogenic bacteria. Modern industrialized food production adds extra emphasis on lowering the use of antibiotics in all parts of agriculture, husbandry and fish farming because these food products are distributed to very large numbers of humans compared to more traditional smaller scale niche production. | 2002 | 12222637 |
| 4046 | 13 | 0.9999 | Horizontal Gene Transfer and Its Association with Antibiotic Resistance in the Genus Aeromonas spp. The evolution of multidrug resistant bacteria to the most diverse antimicrobials known so far pose a serious problem to global public health. Currently, microorganisms that develop resistant phenotypes to multiple drugs are associated with high morbidity and mortality. This resistance is encoded by a group of genes termed 'bacterial resistome', divided in intrinsic and extrinsic resistome. The first one refers to the resistance displayed on an organism without previous exposure to an antibiotic not involving horizontal genetic transfer, and it can be acquired via mutations. The latter, on the contrary, is acquired exclusively via horizontal genetic transfer involving mobile genetic elements that constitute the 'bacterial mobilome'. This transfer is mediated by three different mechanisms: transduction, transformation, and conjugation. Recently, a problem of public health due to implications in the emergence of multi-drug resistance in Aeromonas spp. strains in water environments has been described. This is derived from the genetic material transfer via conjugation events. This is important, since bacteria that have acquired antibiotic resistance in natural environments can cause infections derived from their ingestion or direct contact with open wounds or mucosal tissue, which in turn, by their resistant nature, makes their eradication complex. Implications of the emergence of resistance in Aeromonas spp. by horizontal gene transfer on public health are discussed. | 2019 | 31540466 |
| 4030 | 14 | 0.9999 | The human microbiome as a reservoir of antimicrobial resistance. The gut microbiota is amongst the most densely populated microbial ecosystem on earth. While the microbiome exerts numerous health beneficial functions, the high density of micro-organisms within this ecosystem also facilitates horizontal transfer of antimicrobial resistance (AMR) genes to potential pathogenic bacteria. Over the past decades antibiotic susceptibility testing of specific indicator bacteria from the microbiome, such as Escherichia coli, has been the method of choice in most studies. These studies have greatly enlarged our understanding on the prevalence and distribution of AMR and associated risk factors. Recent studies using (functional) metagenomics, however, highlighted the unappreciated diversity of AMR genes in the human microbiome and identified genes that had not been described previously. Next to metagenomics, more targeted approaches such as polymerase chain reaction for detection and quantification of AMR genes within a population are promising, in particular for large-scale epidemiological screening. Here we present an overview of the indigenous microbiota as a reservoir of AMR genes, the current knowledge on this "resistome" and the recent and upcoming advances in the molecular diagnostic approaches to unravel this reservoir. | 2013 | 23616784 |
| 4007 | 15 | 0.9999 | Detecting horizontal gene transfer among microbiota: an innovative pipeline for identifying co-shared genes within the mobilome through advanced comparative analysis. Horizontal gene transfer (HGT) is a key driver in the evolution of bacterial genomes. The acquisition of genes mediated by HGT may enable bacteria to adapt to ever-changing environmental conditions. Long-term application of antibiotics in intensive agriculture is associated with the dissemination of antibiotic resistance genes among bacteria with the consequences causing public health concern. Commensal farm-animal-associated gut microbiota are considered the reservoir of the resistance genes. Therefore, in this study, we identified known and not-yet characterized mobilized genes originating from chicken and porcine fecal samples using our innovative pipeline followed by network analysis to provide appropriate visualization to support proper interpretation. | 2024 | 38099617 |
| 4192 | 16 | 0.9999 | Food and human gut as reservoirs of transferable antibiotic resistance encoding genes. The increase and spread of antibiotic resistance (AR) over the past decade in human pathogens has become a worldwide health concern. Recent genomic and metagenomic studies in humans, animals, in food and in the environment have led to the discovery of a huge reservoir of AR genes called the resistome that could be mobilized and transferred from these sources to human pathogens. AR is a natural phenomenon developed by bacteria to protect antibiotic-producing bacteria from their own products and also to increase their survival in highly competitive microbial environments. Although antibiotics are used extensively in humans and animals, there is also considerable usage of antibiotics in agriculture, especially in animal feeds and aquaculture. The aim of this review is to give an overview of the sources of AR and the use of antibiotics in these reservoirs as selectors for emergence of AR bacteria in humans via the food chain. | 2013 | 23805136 |
| 4121 | 17 | 0.9999 | Assessment of bacterial antibiotic resistance transfer in the gut. We assessed horizontal gene transfer between bacteria in the gastrointestinal (GI) tract. During the last decades, the emergence of antibiotic resistant strains and treatment failures of bacterial infections have increased the public awareness of antibiotic usage. The use of broad spectrum antibiotics creates a selective pressure on the bacterial flora, thus increasing the emergence of multiresistant bacteria, which results in a vicious circle of treatments and emergence of new antibiotic resistant bacteria. The human gastrointestinal tract is a massive reservoir of bacteria with a potential for both receiving and transferring antibiotic resistance genes. The increased use of fermented food products and probiotics, as food supplements and health promoting products containing massive amounts of bacteria acting as either donors and/or recipients of antibiotic resistance genes in the human GI tract, also contributes to the emergence of antibiotic resistant strains. This paper deals with the assessment of antibiotic resistance gene transfer occurring in the gut. | 2011 | 21318188 |
| 4049 | 18 | 0.9999 | The Plasmidome of Firmicutes: Impact on the Emergence and the Spread of Resistance to Antimicrobials. The phylum Firmicutes is one of the most abundant groups of prokaryotes in the microbiota of humans and animals and includes genera of outstanding relevance in biomedicine, health care, and industry. Antimicrobial drug resistance is now considered a global health security challenge of the 21st century, and this heterogeneous group of microorganisms represents a significant part of this public health issue.The presence of the same resistant genes in unrelated bacterial genera indicates a complex history of genetic interactions. Plasmids have largely contributed to the spread of resistance genes among Staphylococcus, Enterococcus, and Streptococcus species, also influencing the selection and ecological variation of specific populations. However, this information is fragmented and often omits species outside these genera. To date, the antimicrobial resistance problem has been analyzed under a "single centric" perspective ("gene tracking" or "vehicle centric" in "single host-single pathogen" systems) that has greatly delayed the understanding of gene and plasmid dynamics and their role in the evolution of bacterial communities.This work analyzes the dynamics of antimicrobial resistance genes using gene exchange networks; the role of plasmids in the emergence, dissemination, and maintenance of genes encoding resistance to antimicrobials (antibiotics, heavy metals, and biocides); and their influence on the genomic diversity of the main Gram-positive opportunistic pathogens under the light of evolutionary ecology. A revision of the approaches to categorize plasmids in this group of microorganisms is given using the 1,326 fully sequenced plasmids of Gram-positive bacteria available in the GenBank database at the time the article was written. | 2015 | 26104702 |
| 4004 | 19 | 0.9999 | Diverse Distribution of Resistomes in the Human and Environmental Microbiomes. The routine therapeutic use of antibiotics has caused resistance genes to be disseminated across microbial populations. In particular, bacterial strains having antibiotic resistance genes are frequently observed in the human microbiome. Moreover, multidrug-resistant pathogens are now widely spread, threatening public health. Such genes are transferred and spread among bacteria even in different environments. Advances in high throughput sequencing technology and computational algorithms have accelerated investigation into antibiotic resistance genes of bacteria. Such studies have revealed that the antibiotic resistance genes are located close to the mobility-associated genes, which promotes their dissemination. An increasing level of information on genomic sequences of resistome should expedite research on drug-resistance in our body and environment, thereby contributing to the development of public health policy. In this review, the high prevalence of antibiotic resistance genes and their exchange in the human and environmental microbiome is discussed with respect to the genomic contents. The relationships among diverse resistomes, related bacterial species, and the antibiotics are reviewed. In addition, recent advances in bioinformatics approaches to investigate such relationships are discussed. | 2018 | 30532649 |