Phage particles harboring antibiotic resistance genes in fresh-cut vegetables and agricultural soil. - Related Documents




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345601.0000Phage particles harboring antibiotic resistance genes in fresh-cut vegetables and agricultural soil. Bacteriophages are ubiquitously distributed prokaryotic viruses that are more abundant than bacteria. As a consequence of their life cycle, phages can kidnap part of their host's genetic material, including antibiotic resistance genes (ARGs), which released phage particles transfer in a process called transduction. The spread of ARGs among pathogenic bacteria currently constitutes a serious global health problem. In this study, fresh vegetables (lettuce, spinach and cucumber), and cropland soil were screened by qPCR for ten ARGs (bla(TEM), bla(CTX-M-1) group, bla(CTX-M-9) group, bla(OXA-48), bla(VIM), mecA, sul1, qnrA, qnrS and armA) in their viral DNA fraction. The presence of ARGs in the phage DNA was analyzed before and after propagation experiments in an Escherichia coli host strain to evaluate the ability of the phage particles to infect a host. ARGs were found in the phage DNA fraction of all matrices, although with heterogeneous values. ARG prevalence was significantly higher in lettuce and soil, and the most common overall were β-lactamases. After propagation experiments, an increase in ARG densities in phage particles was observed in samples of all four matrices, confirming that part of the isolated phage particles were infectious. This study reveals the abundance of free, replicative ARG-containing phage particles in vegetable matrices and cropland soil. The particles are proposed as vehicles for resistance transfer in these environments, where they can persist for a long time, with the possibility of generating new resistant bacterial strains. Ingestion of these mobile genetic elements may also favor the emergence of new resistances, a risk not previously considered.201829567433
345510.9999Quantifying nonspecific TEM beta-lactamase (blaTEM) genes in a wastewater stream. To control the antibiotic resistance epidemic, it is necessary to understand the distribution of genetic material encoding antibiotic resistance in the environment and how anthropogenic inputs, such as wastewater, affect this distribution. Approximately two-thirds of antibiotics administered to humans are beta-lactams, for which the predominant bacterial resistance mechanism is hydrolysis by beta-lactamases. Of the beta-lactamases, the TEM family is of overriding significance with regard to diversity, prevalence, and distribution. This paper describes the design of DNA probes universal for all known TEM beta-lactamase genes and the application of a quantitative PCR assay (also known as Taqman) to quantify these genes in environmental samples. The primer set was used to study whether sewage, both treated and untreated, contributes to the spread of these genes in receiving waters. It was found that while modern sewage treatment technologies reduce the concentrations of these antibiotic resistance genes, the ratio of bla(TEM) genes to 16S rRNA genes increases with treatment, suggesting that bacteria harboring bla(TEM) are more likely to survive the treatment process. Thus, beta-lactamase genes are being introduced into the environment in significantly higher concentrations than occur naturally, creating reservoirs of increased resistance potential.200918997031
368220.9999Concentration of facultative pathogenic bacteria and antibiotic resistance genes during sewage treatment and in receiving rivers. Whereas the hygienic condition of drinking and bathing water by law must be monitored by culture-based methods, for quantification of microbes and antibiotic resistance in soil or the aquatic environment, often molecular genetic assays are used. For comparison of both methods, knowledge of their correlation is necessary. Therefore the population of total bacteria, Escherichia coli, enterococci and staphylococci during sewage treatment and in receiving river water was compared by agar plating and quantitative polymerase chain reaction (qPCR) assays. In parallel, all samples were investigated for clinically relevant antibiotic resistance genes. Whereas plating and qPCR data for total bacteria correlated well in sewage after primary treatment, qPCR data of river water indicated higher cell numbers for E. coli. It is unknown if these cells are 'only' not growing under standard conditions or if they are dead. Corresponding to the amount of non-culturable cells, the 'breakpoints' for monitoring water quality should be adapted. The abundances of clinically relevant antibiotic resistance genes in river water were in the same order of magnitude or even higher than in treated sewage. For estimation of the health risk it is important to investigate which species carry respective genes and whether these genes are disseminated via gene transfer.201627789876
368130.9999A closer look at the antibiotic-resistant bacterial community found in urban wastewater treatment systems. The conventional biological treatment process can provide a favorable environment for the maintenance and dissemination of antibiotic-resistant bacteria and the antibiotic resistance genes (ARG) they carry. This study investigated the occurrence of antibiotic resistance in three wastewater treatment plants (WWTP) to determine the role they play in the dissemination of ARGs. Bacterial isolates resistant to tetracycline were collected, and tested against eight antibiotics to determine their resistance profiles and the prevalence of multiple antibiotic resistance. It was found that bacteria resistant to tetracycline were more likely to display resistance to multiple antibiotics compared to those isolates that were not tetracycline resistant. Polymerase chain reaction (PCR) was used to identify the tetracycline resistance determinants present within the bacterial communities of the WWTPs and receiving waters, and it was found that ARGs may not be released from the treatment process. Identification of isolates showed that there was a large diversity of species in both the tetracycline-resistant and tetracycline-sensitive populations and that the two groups were significantly different in composition. Antibiotic resistance profiles of each population showed that a large diversity of resistance patterns existed within genera suggesting that transmission of ARG may progress by both horizontal gene and vertical proliferation.201829484827
368040.9999Metagenomic Insights Into the Contribution of Phages to Antibiotic Resistance in Water Samples Related to Swine Feedlot Wastewater Treatment. In this study, we examined the types of antibiotic resistance genes (ARGs) possessed by bacteria and bacteriophages in swine feedlot wastewater before and after treatment using a metagenomics approach. We found that the relative abundance of ARGs in bacterial DNA in all water samples was significantly higher than that in phages DNA (>10.6-fold), and wastewater treatment did not significantly change the relative abundance of bacterial- or phage-associated ARGs. We further detected the distribution and diversity of the different types of ARGs according to the class of antibiotics to which they confer resistance, the tetracycline resistance genes were the most abundant resistance genes and phages were more likely to harbor ATP-binding cassette transporter family and ribosomal protection genes. Moreover, the colistin resistance gene mcr-1 was also detected in the phage population. When assessing the contribution of phages in spreading different groups of ARGs, β-lactamase resistance genes had a relatively high spreading ability even though the abundance was low. These findings possibly indicated that phages not only could serve as important reservoir of ARG but also carry particular ARGs in swine feedlot wastewater, and this phenomenon is independent of the environment.201830459724
368350.9999Small and large-scale distribution of four classes of antibiotics in sediment: association with metals and antibiotic resistance genes. Antibiotic chemicals and antibiotic resistance genes enter the environment via wastewater effluents as well as from runoff from agricultural operations. The relative importance of these two sources, however, is largely unknown. The relationship between the concentrations of chemicals and genes requires exploration, for antibiotics in the environment may lead to development or retention of resistance genes by bacteria. The genes that confer resistance to metal toxicity may also be important in antibiotic resistance. In this work, concentrations of 19 antibiotics (using liquid chromatography tandem mass spectrometry), 14 metals (using inductively coupled plasma-mass spectrometry), and 45 metal, antibiotic, and antibiotic-resistance associated genes (using a multiplex, microfluidic quantitative polymerase chain reaction method) were measured in 13 sediment samples from two large rivers as well as along a spatial transect in a wastewater effluent-impacted lake. Nine of the antibiotics were detected in the rivers and 13 were detected in the lake. Sixteen different resistance genes were detected. The surrounding land use and proximity to wastewater treatment plants are important factors in the number and concentrations of antibiotics detected. Correlations among antibiotic chemical concentrations, metal concentrations, and resistance genes occur over short spatial scales in a lake but not over longer distances in major rivers. The observed correlations likely result from the chemicals and resistance genes arising from the same source, and differences in fate and transport over larger scales lead to loss of this relationship.201830043816
345960.9999Diversity of antibiotic resistance gene variants at subsequent stages of the wastewater treatment process revealed by a metagenomic analysis of PCR amplicons. Wastewater treatment plants have been recognised as point sources of various antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) which are considered recently emerging biological contaminants. So far, culture-based and molecular-based methods have been successfully applied to monitor antimicrobial resistance (AMR) in WWTPs. However, the methods applied do not permit the comprehensive identification of the true diversity of ARGs. In this study we applied next-generation sequencing for a metagenomic analysis of PCR amplicons of ARGs from the subsequent stages of the analysed WWTP. The presence of 14 genes conferring resistance to different antibiotic families was screened by PCR. In the next step, three genes were selected for detailed analysis of changes of the profile of ARG variants along the process. A relative abundance of 79 variants was analysed. The highest diversity was revealed in the ermF gene, with 52 variants. The relative abundance of some variants changed along the purification process, and some ARG variants might be present in novel hosts for which they were currently unassigned. Additionally, we identified a pool of novel ARG variants present in the studied WWTP. Overall, the results obtained indicated that the applied method is sufficient for analysing ARG variant diversity.202338274111
346670.9999Behavior of last resort antibiotic resistance genes (mcr-1 and bla(NDM-1)) in a drinking water supply system and their possible acquisition by the mouse gut flora. Mcr-1 and bla(NDM-1) antibiotic resistance genes (ARGs) confer resistance to colistins and carbapenems, which are often antibiotics used as a last resort in tertiary care hospitals. Dissemination of these two ARGs in drinking water supply systems and their effect on healthy gut bacteria are poorly studied. In this study, the dissemination of mcr-1 and bla(NDM-1) in a drinking water supply system, and their effect on the antibiotic resistance of mouse gut bacteria are explored. Metagenome analysis revealed that source water (Taipu river and Jinze reservoir) was polluted with ARGs. Mcr-1 and bla(NDM-1) can be disseminated through the water distribution system. Even advanced water treatments (ozone and biological activated carbon (BAC)) could not effectively remove mcr-1 and bla(NDM-1). Low concentrations of chloramine disinfectants in the water distribution system were not effective at limiting ARG abundance. Mobile genetic elements were also found to play a major role in the dissemination of ARGs via horizontal gene transfer (HGT) throughout the water supply system. Statistical analysis revealed that there was no effect of temperature on the abundance of mcr-1 and bla(NDM-1) throughout the water supply system. A last resort ARG, mcr-1 can disseminate from drinking water to the healthy mouse gut. The presence of mcr-1 in a strain belonging to Enterococcus hirae, which is different from the strain belonging to the Bacillus cereus group isolated from drinking water, strongly supports the phenomena of HGT inside the gut. This research provides novel insights into the role of drinking water in disseminating ARGs to the gut and strongly suggests that drinking water may also play a major role apart from other factors known to be involved in the prevalence of last resort ARGs in the gut.202031896482
346980.9999Antibiotic resistance genes of emerging concern in municipal and hospital wastewater from a major Swedish city. The spread of antibiotic resistance among bacterial pathogens is to a large extent mediated by mobile antibiotic resistance genes (ARGs). The prevalence and geographic distribution of several newly discovered ARGs, as well as some clinically important ARGs conferring resistance to last resort antibiotics, are largely unknown. Targeted analysis of wastewater samples could allow estimations of carriage in the population connected to the sewers as well as release to the environment. Here we quantified ARGs conferring resistance to linezolid (optrA and cfr(A)) and colistin (mcr-1, -2, -3, -4 and -5) and the recently discovered gar (aminoglycoside ARG) and sul4 (sulphonamide ARG) in raw hospital and municipal wastewater as well as treated municipal wastewater during five years in a low antibiotic resistance prevalence setting (Gothenburg, Sweden). Additionally, variations in bacterial composition of the wastewaters characterized by 16S rRNA sequencing were related to the variations of the ARGs in an attempt to reveal if the presence of known or suspected bacterial host taxa could explain the presence of the ARGs in wastewater. The mcr-1, mcr-3, mcr-4, mcr-5, sul4 and gar genes were detected regularly in all types of wastewater samples while optrA and cfr(A) were detected only in hospital wastewater. The most abundant genes were mcr-3 and mcr-5, especially in municipal wastewater. The detection of optrA was restricted to a peak during one year. Most of the ARGs correlated with taxa previously described as bacterial hosts and associated with humans. Although some of the tentative hosts may include bacteria also thriving in wastewater environments, detection of the ARGs in the wastewaters could reflect their presence in the gut flora of the contributing populations. If so, they could already today or in the near future hinder treatment of bacterial infections in a setting where they currently are rarely targeted/detected during clinical surveillance.202234748849
656990.9999Unveiling Rare Pathogens and Antibiotic Resistance in Tanzanian Cholera Outbreak Waters. The emergence of antibiotic resistance is a global health concern. Therefore, understanding the mechanisms of its spread is crucial for implementing evidence-based strategies to tackle resistance in the context of the One Health approach. In developing countries where sanitation systems and access to clean and safe water are still major challenges, contamination may introduce bacteria and bacteriophages harboring antibiotic resistance genes (ARGs) into the environment. This contamination can increase the risk of exposure and community transmission of ARGs and infectious pathogens. However, there is a paucity of information on the mechanisms of bacteriophage-mediated spread of ARGs and patterns through the environment. Here, we deploy Droplet Digital PCR (ddPCR) and metagenomics approaches to analyze the abundance of ARGs and bacterial pathogens disseminated through clean and wastewater systems. We detected a relatively less-studied and rare human zoonotic pathogen, Vibrio metschnikovii, known to spread through fecal--oral contamination, similarly to V. cholerae. Several antibiotic resistance genes were identified in both bacterial and bacteriophage fractions from water sources. Using metagenomics, we detected several resistance genes related to tetracyclines and beta-lactams in all the samples. Environmental samples from outlet wastewater had a high diversity of ARGs and contained high levels of blaOXA-48. Other identified resistance profiles included tetA, tetM, and blaCTX-M9. Specifically, we demonstrated that blaCTX-M1 is enriched in the bacteriophage fraction from wastewater. In general, however, the bacterial community has a significantly higher abundance of resistance genes compared to the bacteriophage population. In conclusion, the study highlights the need to implement environmental monitoring of clean and wastewater to inform the risk of infectious disease outbreaks and the spread of antibiotic resistance in the context of One Health.202337894148
7105100.9999Estimating the contribution of bacteriophage to the dissemination of antibiotic resistance genes in pig feces. The transfer of antibiotic resistance genes (ARGs) in the environment is a threat to both human and animal health. However, the contribution of bacteriophages to the dissemination of resistance genes via transduction is rarely explored. In this study, we screened pig feces from three commercial farms in China for 32 clinically relevant ARG types to assess the presence of the ARG population in bacteria and bacteriophage and further to estimate the contribution of bacteriophages to the dissemination of antibiotic resistance. We found that bacteriophage DNA contained 35.5% of the target ARG types and sul1, bla(TEM) and ermB were found in 100% of the phage DNA samples. The most abundant genes in the bacterial population were ermB and fexA whereas ermB was the most abundant in bacteriophage. In contrast, floR was the least abundant ARG in both populations. Also, the ratio index of the abundance of ARGs in bacteriophage and bacteria was firstly used in this study as an estimator of bacteriophage ability to transmit ARGs. The ratio for qnrA was the greatest (about 10(-1)) and differed from the most abundant bacteriophage ARG ermB. In addition, fexA had the lowest ratio value (about 10(-6)) and not floR. These results illustrate that ARGs abundance and detection rates used alone probably be not suitable for comprehensively judging the contribution of bacteriophage to the dissemination of antibiotic resistance. A more suitable model is the application of three indices; occurrence rate, absolute abundance in bacteriophage and the ratio value as warning and monitoring tools for environmental ARG assessments in bacteriophages.201829573711
3468110.9999Facultative pathogenic bacteria and antibiotic resistance genes in swine livestock manure and clinical wastewater: A molecular biology comparison. Manure contains vast amounts of biological contaminants of veterinary origin. Only few studies analyse clinically critical resistance genes against reserve antibiotics in manure. In general, resistances against these high priority antibiotics involve a high potential health risk. Therefore, their spread in the soil as well as the aquatic environment has to be prevented. Manures of 29 different swine livestock were analysed. Abundances of facultative pathogenic bacteria including representatives of the clinically critical ESKAPE-pathogens (P. aeruginosa, K. pneumoniae, A. baumannii, E. faecium) and E. coli were investigated via qPCR. Antibiotic resistance genes against commonly used veterinary antibiotics (ermB, tetM, sul1) as well as various resistance genes against important (mecA, vanA) and reserve antibiotics (bla(NDM), bla(KPC3), mcr-1), which are identified by the WHO, were also obtained by qPCR analysis. The manures of all swine livestock contained facultative pathogenic bacteria and commonly known resistance genes against antibiotics used in veterinary therapies, but more important also a significant amount of clinically critical resistance genes against reserve antibiotics for human medicine. To illustrate the impact the occurrence of these clinically critical resistance genes, comparative measurements were taken of the total wastewater of a large tertiary care hospital (n = 8). Both manure as well as raw hospital wastewaters were contaminated with significant abundances of gene markers for facultative pathogens and with critical resistance genes of reserve antibiotics associated with genetic mobile elements for horizontal gene transfer. Hence, both compartments bear an exceptional potential risk for the dissemination of facultative pathogens and critical antibiotic resistance genes.202236089145
7397120.9999Persistence of naturally occurring antibiotic resistance genes in the bacteria and bacteriophage fractions of wastewater. The emergence and prevalence of antibiotic resistance genes (ARGs) in the environment is a serious global health concern. ARGs from bacteria can be mobilized by mobile genetic elements, and recent studies indicate that phages and phage-derived particles, among others, could play a role in the spread of ARGs through the environment. ARGs are abundant in the bacterial and bacteriophage fractions of water bodies and for successful transfer of the ARGs, their persistence in these environments is crucial. In this study, three ARGs (blaTEM, blaCTX-M and sul1) that naturally occur in the bacterial and phage fractions of raw wastewater were used to evaluate the persistence of ARGs at different temperatures (4 °C, 22 °C and 37 °C) and pH values (3, 7 and 9), as well as after various disinfection treatments (thermal treatment, chlorination and UV) and natural inactivation in a mesocosm. Gene copies (GC) were quantified by qPCR; then the logarithmic reduction and significance of the differences between their numbers were evaluated. The ARGs persisted for a long time with minimal reductions after all the treatments. In general, they showed greater persistence in the bacteriophage fraction than in the bacterial fraction. Comparisons showed that the ARGs persisted under conditions that reduced culturable Escherichia coli and infectious coliphages below the limit of detection. The prevalence of ARGs, particularly in the bacteriophage fraction, poses the threat of the spread of ARGs and their incorporation into a new bacterial background that could lead to the emergence of new resistant clones.201626978717
3454130.9999Antibiotic Resistance Genes in Phage Particles from Antarctic and Mediterranean Seawater Ecosystems. Anthropogenic activities are a key factor in the development of antibiotic resistance in bacteria, a growing problem worldwide. Nevertheless, antibiotics and resistances were being generated by bacterial communities long before their discovery by humankind, and might occur in areas without human influence. Bacteriophages are known to play a relevant role in the dissemination of antibiotic resistance genes (ARGs) in aquatic environments. In this study, five ARGs (bla(TEM), bla(CTX-M-1), bla(CTX-M-9), sul1 and tetW) were monitored in phage particles isolated from seawater of two different locations: (i) the Mediterranean coast, subjected to high anthropogenic pressure, and (ii) the Antarctic coast, where the anthropogenic impact is low. Although found in lower quantities, ARG-containing phage particles were more prevalent among the Antarctic than the Mediterranean seawater samples and Antarctic bacterial communities were confirmed as their source. In the Mediterranean area, ARG-containing phages from anthropogenic fecal pollution might allow ARG transmission through the food chain. ARGs were detected in phage particles isolated from fish (Mediterranean, Atlantic, farmed, and frozen), the most abundant being β-lactamases. Some of these particles were infectious in cultures of the fecal bacteria Escherichia coli. By serving as ARG reservoirs in marine environments, including those with low human activity, such as the Antarctic, phages could contribute to ARG transmission between bacterial communities.202032847015
7395140.9999Impacts of anthropogenic activity on the ecology of class 1 integrons and integron-associated genes in the environment. The impact of human activity on the selection for antibiotic resistance in the environment is largely unknown, although considerable amounts of antibiotics are introduced through domestic wastewater and farm animal waste. Selection for resistance may occur by exposure to antibiotic residues or by co-selection for mobile genetic elements (MGEs) which carry genes of varying activity. Class 1 integrons are genetic elements that carry antibiotic and quaternary ammonium compound (QAC) resistance genes that confer resistance to detergents and biocides. This study aimed to investigate the prevalence and diversity of class 1 integron and integron-associated QAC resistance genes in bacteria associated with industrial waste, sewage sludge and pig slurry. We show that prevalence of class 1 integrons is higher in bacteria exposed to detergents and/or antibiotic residues, specifically in sewage sludge and pig slurry compared with agricultural soils to which these waste products are amended. We also show that QAC resistance genes are more prevalent in the presence of detergents. Studies of class 1 integron prevalence in sewage sludge amended soil showed measurable differences compared with controls. Insertion sequence elements were discovered in integrons from QAC contaminated sediment, acting as powerful promoters likely to upregulate cassette gene expression. On the basis of this data, >1 × 10(19) bacteria carrying class 1 integrons enter the United Kingdom environment by disposal of sewage sludge each year.201121368907
3423150.9999bla(TEM) and vanA as indicator genes of antibiotic resistance contamination in a hospital-urban wastewater treatment plant system. Four indicator genes were monitored by quantitative PCR in hospital effluent (HE) and in the raw and treated wastewater of the municipal wastewater treatment plant receiving the hospital discharge. The indicator genes were the class 1 integrase gene intI1, to assess the capacity of bacteria to be involved in horizontal gene transfer processes; bla(TEM), one of the most widespread antibiotic resistance genes in the environment, associated with Enterobacteriaceae; vanA, an antibiotic resistance gene uncommon in the environment and frequent in clinical isolates; and marA, part of a locus related to the stress response in Enterobacteriaceae. Variation in the abundance of these genes was analysed as a function of the type of water, and possible correlations with cultivable bacteria, antimicrobial residue concentrations, and bacterial community composition and structure were analysed. HE was confirmed as an important source of bla(TEM) and vanA genes, and wastewater treatment showed a limited capacity to remove these resistance genes. The genes bla(TEM) and vanA presented the strongest correlations with culturable bacteria, antimicrobial residues and some bacterial populations, representing interesting candidates as indicator genes to monitor resistance in environmental samples. The intI1 gene was the most abundant in all samples, demonstrating that wastewater bacterial populations hold a high potential for gene acquisition.201427873693
7400160.9999Investigating the effects of municipal and hospital wastewaters on horizontal gene transfer. Horizontal gene transfer (HGT) plays an important role in the dissemination of antibiotic resistance genes. In sewer systems, human-associated and environmental bacteria are mixed together and exposed to many substances known to increase HGT, including various antibacterial compounds. In wastewaters, those substances are most often detected below concentrations known to induce HGT individually. Still, it is possible that such wastewaters induce HGT, for example via mixture effects. Here, a panel of antibiotics, biocides and other pharmaceuticals was measured in filter-sterilized municipal and hospital wastewater samples from Gothenburg, Sweden. The effects on HGT of the chemical mixtures in these samples were investigated by exposing a complex bacterial donor community together with a GFP-tagged E. coli recipient strain. Recipients that captured sulfonamide resistance-conferring mobile genetic elements (MGEs) from the bacterial community were enumerated and characterized by replicon typing, antibiotic susceptibility testing and long read sequencing. While exposure to municipal wastewater did not result in any detectable change in HGT rates, exposure to hospital wastewater was associated with an increase in the proportion of recipients that acquired sulfonamide resistance but also a drastic decrease in the total number of recipients. Although, concentrations were generally higher in hospital than municipal wastewater, none of the measured substances could individually explain the observed effects of hospital wastewater. The great majority of the MGEs captured were IncN plasmids, and resistance to several antibiotics was co-transferred in most cases. Taken together, the data show no evidence that chemicals present in the studied municipal wastewater induce HGT. Still, the increased relative abundance of transconjugants after exposure to hospital wastewater could have implications for the risks of both emergence and transmission of resistant bacteria.202133631686
3424170.9999Contribution of bacteriophage and plasmid DNA to the mobilization of antibiotic resistance genes in a river receiving treated wastewater discharges. In this study, we quantified eleven antibiotic compounds and nine antibiotic resistance genes (ARGs) in water samples collected upstream and downstream of the discharge point from a municipal wastewater treatment plant (WWTP) into the Ter River. Antibiotics were analyzed by liquid chromatography coupled to mass spectrometry, whereas the concentration of ARGs in bacterial, phage and plasmid DNA fractions was determined by real-time PCR to explore their contribution to environmental antibiotic resistance. WWTP discharges resulted in higher concentrations of antibiotic residues as well as ARGs in water samples collected downstream the impact point. Specifically, genes conferring resistance to macrolides (ermB), fluoroquinolones (qnrS) and tetracyclines (tetW) showed significant differences (p<0.05) between upstream and downstream sites in the three DNA fractions (i.e. bacteria, plasmids and phages). Interestingly, genes conferring resistance to β-lactams (bla(TEM), bla(NDM) and bla(KPC)) and glycopeptides (vanA) only showed significant differences (p<0.05) between upstream and downstream sites in phage and plasmid DNA but not in the bacterial DNA fraction. Our results show for the first time the extent to which phages and plasmids contribute to the mobilization of ARGs in an aquatic environment exposed to chronic antibiotic pollution via WWTP discharges. Accordingly, these mobile genetic elements should be included in further studies to get a global view of the spread of antibiotic resistance.201728551539
7396180.9998Antibiotic resistant bacteria and resistance genes in the bottom sediment of a small stream and the potential impact of remobilization. River sediments are regarded as hot spots of bacterial density and activity. Moreover, high bacterial densities and biofilm formation are known to promote horizontal gene transfer, the latter playing a vital role in the spread of antimicrobial resistance. It can thus be hypothesized that sediments act as a reservoir of antibiotic resistant bacteria (ARB) and resistance genes (ARGs), particularly in rivers receiving microbes and drug residues from treated sewage. We analyzed the phenotypic susceptibility of 782 Escherichia coli isolates against 24 antimicrobials and we measured the relative abundances of five ARGs in water and sediment extracts of a small stream. We did not find evidence for a general increase in the proportion of resistant E. coli isolated from sediments as compared to those found in stream water. For most antimicrobials, the likelihood of detecting a resistant isolate was similar in water and sediment or it was even lower in the latter compartment. The mean relative abundance of ARGs was moderately increased in sediment-borne samples. Generally, absolute abundances of resistant cells and resistance genes in the sediment exceeded the pelagic level owing to higher bacterial densities. The river bottom thus represents a reservoir of ARB and ARGs that can be mobilized by resuspension.201829982428
7324190.9998Microbial and Viral Communities and Their Antibiotic Resistance Genes Throughout a Hospital Wastewater Treatment System. Antibiotic resistance poses a serious threat to global public health, and antibiotic resistance determinants can enter natural aquatic systems through discharge of wastewater effluents. Hospital wastewater in particular is expected to contain high abundances of antibiotic resistance genes (ARGs) compared to municipal wastewater because it contains human enteric bacteria that may include antibiotic-resistant organisms originating from hospital patients, and can also have high concentrations of antibiotics and antimicrobials relative to municipal wastewater. Viruses also play an important role in wastewater treatment systems since they can influence the bacterial community composition through killing bacteria, facilitating transduction of genetic material between organisms, and modifying the chromosomal content of bacteria as prophages. However, little is known about the fate and connections between ARGs, viruses, and their associated bacteria in hospital wastewater systems. To address this knowledge gap, we characterized the composition and persistence of ARGs, dsDNA viruses, and bacteria from influent to effluent in a pilot-scale hospital wastewater treatment system in Israel using shotgun metagenomics. Results showed that ARGs, including genes conferring resistance to antibiotics of high clinical relevance, were detected in all sampling locations throughout the pilot-scale system, with only 16% overall depletion of ARGs per genome equivalent between influent and effluent. The most common classes of ARGs detected throughout the system conferred resistance to aminoglycoside, cephalosporin, macrolide, penam, and tetracycline antibiotics. A greater proportion of total ARGs were associated with plasmid-associated genes in effluent compared to in influent. No strong associations between viral sequences and ARGs were identified in viral metagenomes from the system, suggesting that phage may not be a significant vector for ARG transfer in this system. The majority of viruses in the pilot-scale system belonged to the families Myoviridae, Podoviridae, and Siphoviridae. Gammaproteobacteria was the dominant class of bacteria harboring ARGs and the most common putative viral host in all samples, followed by Bacilli and Betaproteobacteria. In the total bacterial community, the dominant class was Betaproteobacteria for each sample. Overall, we found that a variety of different types of ARGs and viruses were persistent throughout this hospital wastewater treatment system, which can be released to the environment through effluent discharge.202032140141