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752801.0000Horizontal transfer of antibiotic resistance genes in a membrane bioreactor. Growing attention has been paid to the dissemination of antibiotic resistance genes (ARGs) in wastewater microbial communities. The application of membrane bioreactors (MBRs) in wastewater treatment is becoming increasingly widespread. We hypothesized that the transfer of ARGs among bacteria could occur in MBRs, which combine a high density of bacterial cells, biofilms, and antibiotic resistance bacteria or ARGs. In this study, the transfer discipline and dissemination of the RP4 plasmid in MBRs were investigated by the counting plate method, the MIDI microorganism identification system, and quantitative polymerase chain reaction (qPCR) techniques. The results showed that the average transfer frequency of the RP4 plasmid from the donor strain to cultivable bacteria in activated sludge was 2.76×10⁻⁵ per recipient, which was greater than the transfer frequency in wastewater and bacterial sludge reported previously. In addition, many bacterial species in the activated sludge had received RP4 by horizontal transfer, while the genera of Shewanella spp., Photobacterium spp., Pseudomonas spp., Proteus spp., and Vibrio spp. were more likely to acquire this plasmid. Interestingly, the abundance of the RP4 plasmid in total DNA remained at high levels and relatively stable at 10⁴ copies/mg of biosolids, suggesting that ARGs were transferred from donor strains to activated sludge bacteria in our study. Thus, the presence of ARGs in sewage sludge poses a potential health threat.201323942379
752910.9998Fate of Antibiotic Resistant Pseudomonas putida and Broad Host Range Plasmid in Natural Soil Microcosms. Plasmid conjugation is one of the dominant mechanisms of horizontal gene transfer, playing a noticeable role in the rapid spread of antibiotic resistance genes (ARGs). Broad host range plasmids are known to transfer to diverse bacteria in extracted soil bacterial communities when evaluated by filter mating incubation. However, the persistence and dissemination of broad range plasmid in natural soil has not been well studied. In this study, Pseudomonas putida with a conjugative antibiotic resistance plasmid RP4 was inoculated into a soil microcosm, the fate and persistence of P. putida and RP4 were monitored by quantitative PCR. The concentrations of P. putida and RP4 both rapidly decreased within 15-day incubation. P. putida then decayed at a significantly lower rate during subsequent incubation, however, no further decay of RP4 was observed, resulting in an elevated RP4/P. putida ratio (up to 10) after 75-day incubation, which implied potential transfer of RP4 to soil microbiota. We further sorted RP4 recipient bacteria from the soil microcosms by fluorescence-activated cell sorting. Spread of RP4 increased during 75-day microcosm operation and was estimated at around 10(-4) transconjugants per recipient at the end of incubation. Analysis of 16S rRNA gene sequences of transconjugants showed that host bacteria of RP4 were affiliated to more than 15 phyla, with increased diversity and shift in the composition of host bacteria. Proteobacteria was the most dominant phylum in the transconjugant pools. Transient transfer of RP4 to some host bacteria was observed. These results emphasize the prolonged persistence of P. putida and RP4 in natural soil microcosms, and highlight the potential risks of increased spread potential of plasmid and broader range of host bacteria in disseminating ARGs in soil.201930881351
720120.9998Evolution of microbial community and drug resistance during enrichment of tetracycline-degrading bacteria. Recently, the microbial degradation of tetracycline has been widely reported. However, its potential risks in treating wastewater containing high concentrations of tetracycline have not been fully evaluated. In this study, the evolution of the microbial community and drug resistance was traced during the enrichment of tetracycline-degrading bacteria. The results showed that some minor compositions such as Shewanella, Bacillus, and Pseudomonas in the seed sludge became the predominant genera in the enrichment cultures when continuously using tetracycline as the sole carbon source, especially some possible pathogenic bacteria increased significantly in this process. The abundances of most TRGs/16S rDNA were increased after enrichment, although the relative abundance of tetA and tetL genes decreased to some extent. From the enrichment culture, 7 predominant tetracycline-degrading strains were isolated, of which TD-1 (Bacillus) and TD-5 (Shewanella) presented high degradation efficiencies (6-day degradation rate > 95%, half-life period of tetracycline ≈ 24 h). In addition, multiple TRGs, mobile genetic elements (MGEs) and even gene cassettes were found in each tetracycline-degrading isolate. The findings suggested that some risks such as the pathogenicity of isolates and the spread of ARGs should be considered when the biodegradation method is used to treat wastewater polluted with high concentrations of tetracycline.201930660087
384530.9998A novel microfluidic system enables visualization and analysis of antibiotic resistance gene transfer to activated sludge bacteria in biofilm. Antibiotic resistance genes (ARGs) in environment have become a growing public concern, due to their potential to be obtained by pathogens and their duplication along cell division. Horizontal gene transfer (HGT) was reported to be responsible for ARGs dissemination in microbes, but the HGT feature in environmental biofilm was still unclear due to insufficient assay tools. To address this challenge, we applied a novel microfluidic system to cultivate thin biofilm by continuous supply of nutrients and close contact between cells. Resembling the living state of biofilm in open environment, this chip visualized the transfer of ARG-encoded plasmids RP4 and pKJK5 to the receptors, e.g., activated sludge bacteria. The average plasmid transfer frequency per receptor (T/R) from RP4-hosted Pseudomonas putida KT2440 to activated sludge bacteria was quantified to be 2.5 × 10(-3) via flow cytometry, and T/R for pKJK5-hosted Escherichia coli MG1655 was 8.9 × 10(-3), while the corresponding average frequencies per donor (T/D) were diverse for the two host strains as 4.3 × 10(-3) and 1.4 × 10(-1) respectively. The difference between T/R and T/D was explained by the plasmid transfer kinetics, implying specific purposes of the two calculations. Finally, we collected the transconjugants by fluorescent activated cell sorting and further sequenced their 16S rDNA. Bacteria from phyla Proteobacteria and Firmicutes were found more susceptible to be transconjugants than those from Bacteroidetes. Our work demonstrated that microfluidic system was advantageous in biofilm HGT study, which can provide more insights into environmental ARG control.201829909325
739940.9998Aquatic animals promote antibiotic resistance gene dissemination in water via conjugation: Role of different regions within the zebra fish intestinal tract, and impact on fish intestinal microbiota. The aqueous environment is one of many reservoirs of antibiotic resistance genes (ARGs). Fish, as important aquatic animals which possess ideal intestinal niches for bacteria to grow and multiply, may ingest antibiotic resistance bacteria from aqueous environment. The fish gut would be a suitable environment for conjugal gene transfer including those encoding antibiotic resistance. However, little is known in relation to the impact of ingested ARGs or antibiotic resistance bacteria (ARB) on gut microbiota. Here, we applied the cultivation method, qPCR, nuclear molecular genetic marker and 16S rDNA amplicon sequencing technologies to develop a plasmid-mediated ARG transfer model of zebrafish. Furthermore, we aimed to investigate the dissemination of ARGs in microbial communities of zebrafish guts after donors carrying self-transferring plasmids that encode ARGs were introduced in aquaria. On average, 15% of faecal bacteria obtained ARGs through RP4-mediated conjugal transfer. The hindgut was the most important intestinal region supporting ARG dissemination, with concentrations of donor and transconjugant cells almost 25 times higher than those of other intestinal segments. Furthermore, in the hindgut where conjugal transfer occurred most actively, there was remarkable upregulation of the mRNA expression of the RP4 plasmid regulatory genes, trbBp and trfAp. Exogenous bacteria seem to alter bacterial communities by increasing Escherichia and Bacteroides species, while decreasing Aeromonas compared with control groups. We identified the composition of transconjugants and abundance of both cultivable and uncultivable bacteria (the latter accounted for 90.4%-97.2% of total transconjugants). Our study suggests that aquatic animal guts contribute to the spread of ARGs in water environments.201728742284
730250.9998Release of Antibiotic Resistant Bacteria by a Waste Treatment Plant from Romania. The occurrence and spread of bacterial antibiotic resistance are subjects of great interest, and the role of wastewater treatment plants has been attracting particular interest. These stations are a reservoir of bacteria, have a large range of organic and inorganic substances, and the amount of bacteria released into the environment is very high. The main purpose of the present study was to assess the removal degree of bacteria with resistance to antibiotics and identify the contribution of a wastewater treatment plant to the microbiota of Someşul Mic river water in Cluj county. The resistance to sulfamethoxazole and tetracycline and some of their representative resistance genes: sul1, tet(O), and tet(W) were assessed in this study. The results obtained showed that bacteria resistant to sulphonamides were more abundant than those resistant to tetracycline. The concentration of bacteria with antibiotic resistance changed after the treatment, namely, bacteria resistant to sulfamethoxazole. The removal of all bacteria and antibiotic-resistant bacteria was 98-99% and the degree of removal of bacteria resistant to tetracycline was higher than the bacteria resistant to sulfamethoxazole compared to total bacteria. The wastewater treatment plant not only contributed to elevating ARG concentrations, it also enhanced the possibility of horizontal gene transfer (HGT) by increasing the abundance of the intI1 gene. Even though the treatment process reduced the concentration of bacteria by two orders of magnitude, the wastewater treatment plant in Cluj-Napoca contributed to an increase in antibiotic-resistant bacteria concentrations up to 10 km downstream of its discharge in Someşul Mic river.201728781345
384460.9998Effects of Nutrient Level and Growth Rate on the Conjugation Process That Transfers Mobile Antibiotic Resistance Genes in Continuous Cultures. Bacteria in the effluent of wastewater treatment plants (WWTPs) can transfer antibiotic resistance genes (ARGs) to the bacteria in receiving water through conjugation; however, there is a lack of quantitative assessment of this phenomenon in continuous cultures. Our objective was to determine the effects of background nutrient levels in river water column and growth rates of bacteria on the conjugation frequency of ARGs from effluent bacteria to river bacteria, as well as on the resulting resistance level (i.e., MICs) of the river bacteria. Chemostats were employed to simulate the discharge points of WWTPs into rivers, where effluent bacteria (donor cells) meet river bacteria (recipient cells). Both donor and recipient cells were Escherichia coli cells, and the donor cells were constructed by filter mating with bacteria in the effluent of a local WWTP. Results showed that higher bacterial growth rate (0.45 h(-1) versus 0.15 h(-1)) led to higher conjugation frequencies (10(-4) versus 10(-6) transconjugant per recipient). The nutrient level also significantly affected the conjugation frequency, albeit to a lesser extent than the growth rate. The MIC against tetracycline increased from 2 mg/L in the recipient to 64 to 128 mg/L in transconjugants. In comparison, the MIC only increased to as high as 8 mg/L in mutants. Whole-genome sequencing showed that the tet-containing plasmid in both the donor and the transconjugant cells also occur in other fecal bacterial genera. The quantitative information obtained from this study can inform hazard identification related to the proliferation of wastewater-associated ARGs in surface water. IMPORTANCE WWTPs have been regarded as an important hot spot of ARGs. The discharge point of WWTP effluent, where ARGs may be horizontally transferred from bacteria of treated wastewater to bacteria of receiving water, is an important interface between the human-dominated ecosystem and the natural environment. The use of batch cultures in previous studies cannot adequately simulate the nutrient conditions and growth rates in receiving water. In this study, chemostats were employed to simulate the continuous growth of bacteria in receiving water. Furthermore, the experimental setup allowed for separate investigations on the effects of nutrient levels (i.e., simulating background nutrients in river water) and bacterial growth rates on conjugation frequencies and resulting resistance levels. The study generates statistically sound ecological data that can be used to estimate the risk of wastewater-originated ARGs as part of the One Health framework.202236094214
731170.9998Sludge as a potential important source of antibiotic resistance genes in both the bacterial and bacteriophage fractions. The emergence and prevalence of antibiotic resistance genes (ARGs) in the environment is a serious global health concern. ARGs found in bacteria can become mobilized in bacteriophage particles in the environment. Sludge derived from secondary treatment in wastewater treatment plants (WWTPs) constitutes a concentrated pool of bacteria and phages that are removed during the treatment process. This study evaluates the prevalence of ARGs in the bacterial and phage fractions of anaerobic digested sludge; five ARGs (blaTEM, blaCTX-M, qnrA, qnrS, and sul1) are quantified by qPCR. Comparison between the wastewater and sludge revealed a shift in the prevalence of ARGs (blaTEM and sul1 became more prevalent in sludge), suggesting there is a change in the bacterial and phage populations from wastewater to those selected during the secondary treatment and the later anaerobic mesophilic digestion of the sludge. ARGs densities were higher in the bacterial than in the phage fraction, with high densities in both fractions; particularly for blaTEM and sul1 (5 and 8 log10 gene copies (GC)/g, respectively, in bacterial DNA; 5.5 and 4.4 log10 GC/g, respectively, in phage DNA). These results question the potential agricultural uses of treated sludge, as it could contribute to the spread of ARGs in the environment and have an impact on the bacterial communities of the receiving ecosystem.201424873655
740080.9998Investigating 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
368090.9998Metagenomic 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
7193100.9998Plasmid-mediated transfer of antibiotic resistance genes and biofilm formation in a simulated drinking water distribution system under chlorine pressure. The effects of disinfectants and plasmid-based antibiotic resistance genes (ARGs) on the growth of microorganisms and the plasmid-mediated transfer of ARGs in the water and biofilm of the drinking water distribution system under simulated conditions were explored. The heterotrophic plate count of the water in reactors with 0.1 mg/L NaClO and NH(2)Cl was higher than in the control groups. There was no similar phenomenon in biofilm. In the water of reactors containing NaClO, the aphA and bla genes were lower than in the antibiotic resistant bacteria group, while both genes were higher in the water of reactors with NH(2)Cl than in the control group. Chloramine may promote the transfer of ARGs in the water phase. Both genes in the biofilm of the reactors containing chlorine were lower than the control group. Correlation analysis between ARGs and water quality parameters revealed that the copy numbers of the aphA gene were significantly positively correlated with the copy numbers of the bla gene in water and significantly negatively correlated in biofilm (p < 0.05). The results of the sequencing assay showed that bacteria in the biofilm, in the presence of disinfectant, were primarily Gram-negative. 1.0 mg/L chlorine decreased the diversity of the community in the biofilm. The relative abundance of some bacteria that may undergo transfer increased in the biofilm of the reactor containing 0.1 mg/L chlorine.202539617560
7530110.9998Enhancing control of multidrug-resistant plasmid and its host community with a prolonged thermophilic phase during composting. The plasmid-mediated horizontal transfer of antibiotic resistance genes (ARGs) among bacteria facilitates the evolution and dissemination of antibiotic resistance. Broad-host-range plasmids can be transferred to different bacterial hosts in soil, plant rhizospheres, and wastewater treatment plants. Although composting is an effective way to convert organic waste into fertilizer and reduce some ARGs, few studies have focused on its effects on the spread of ARG-carrying plasmids and their bacterial host communities during composting. In this study, a fluorescently labeled Pseudomonas putida (P. putida) harboring a broad-host-range plasmid RP4 carrying three ARGs was inoculated into a raw material microcosm and composted with different durations of the thermophilic phase. The fate of the donor and RP4 in composting was investigated. The prolonged thermophilic composting removed 95.1% of dsRed and 98.0% of gfp, and it inhibited the rebound of P. putida and RP4 during the maturation phase. The spread potential of RP4 decreased from 10(-4) to 10(-6) transconjugants per recipient after composting. In addition, we sorted and analyzed the composition of RP4 recipient bacteria using fluorescence-activated cell sorting combined with 16S rRNA gene amplicon sequencing. The recipient bacteria of RP4 belonged to eight phyla, and Firmicutes, accounting for 75.3%-90.1%, was the dominant phylum in the transconjugants. The diversity and richness of the RP4 recipient community were significantly reduced by prolonged thermophilic periods. Overall, these findings provide new insights for assessing the contribution of composting in mitigating the dissemination of plasmid-mediated ARGs, and the prolonged thermophilic phase of composting can limit the transfer of multidrug-resistant plasmids.202236060751
7397120.9998Persistence 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
7383130.9998Spread of plasmids carrying antibiotic resistance genes in soil-lettuce-snail food chain. Fertilization can change the composition of antibiotic resistance genes(ARGs) and their host bacteria in agricultural fields, while complex microbial activities help ARGs into crops and transmit them to humans through agricultural products.Therefore, this study constructed a farmland food chain with soil-lettuce-snail as a typical structure, added genetically engineered Pseudomonas fluorescens containing multidrug-resistant plasmid RP4 to track its spread in the farmland food chain, and used different fertilization methods to explore its influence on the spread and diffusion of ARGs and intl1 in the farmland food chain. It was found that exogenous Pseudomonas can enter plants from soil and pass into snails' intestines, and there is horizontal gene transfer phenomenon of RP4 plasmid in bacteria. At different interfaces of the constructed food chain, the addition of exogenous drug-resistant bacteria had different effects on the total abundance of ARGs and intl1. Fertilization, especially manure, not only promoted the spread of Pseudomonas aeruginosa and the transfer of RP4 plasmid levels, but also significantly increased the total abundance of ARGs and intl1 at all interfaces of the constructed food chain. The main ARGs host bacteria in the constructed food chain include Proteobacteria, Bacteroides, and Firmicutes, while Flavobacterium of Bacteroides is the unique potential host bacteria of RP4 plasmid. In conclusion, this study provides a reference for the risk assessment of ARGs transmitted to the human body through the food chain, and has important practical significance to reduce the antibiotic resistance contamination of agricultural products and ensure the safety of vegetable basket.202438700770
3843140.9998Bacterivorous Ciliate Tetrahymena pyriformis Facilitates vanA Antibiotic Resistance Gene Transfer in Enterococcus faecalis. Background: Wastewater treatment plants (WWTPs) are hotspots for the emergence and spread of antibiotic resistance genes (ARGs). In activated sludge treatment systems, bacterivorous protozoa play a crucial role in biological processes, yet their impact on the horizontal gene transfer in Gram-positive enteric bacteria remains largely unexplored. This study investigated whether the ciliate Tetrahymena pyriformis facilitates the transfer of antibiotic resistance genes between Enterococcus faecalis strains. Methods: Conjugation assays were conducted under laboratory conditions using a vanA-carrying donor and a rifampicin-resistant recipient at an initial bacterial concentration of 10(9) CFU/mL and ciliate density of 10(5) N/mL. Results: Transconjugant numbers peaked at 2 h when experiments started with recipient bacteria harvested in the exponential growth phase, and at 24 h when bacteria were in the stationary phase. In both cases, vanA gene transfer frequency was highest at 24 h (10(-4)-10(-5) CFU/mL), and the presence of energy sources increased gene transfer frequency by one order of magnitude. Conclusions: These findings suggest that ciliate grazing may contribute to vanA gene transfer in WWTP effluents, potentially facilitating its dissemination among permissive bacteria. Given the ecological and public health risks associated with vanA gene persistence in wastewater systems, understanding protozoan-mediated gene transfer is crucial for mitigating the spread of antibiotic resistance in aquatic environments.202540426515
7396150.9998Antibiotic 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
7965160.9998Screening and evaluation of heavy metals facilitating antibiotic resistance gene transfer in a sludge bacterial community. Recent growing evidence suggests that heavy metals can stimulate the transfer of antibiotic resistance genes (ARGs) between bacteria. However, most previous studies focused on pure strains, the effect of heavy metals on ARG transfer in bacterial communities, especially in activated sludge, has not been clearly explored. In this study, a high-throughput method, combining computerized incubator (Bioscreen C) and flow cytometry, was developed to evaluate different concentrations of heavy metals influencing ARG transfer in sludge bacteria communities. By using Escherichia coli MG1655 as the donor of broad-host range IncP-1 plasmid pKJK5, it was found that 0.5 mmol/L Pb, 0.1 mmol/L As and 0.005 mmol/L Hg could obviously promote ARG transfer in sludge bacteria communities. Furthermore, mating assays on microfluidic chips also proved higher transfer frequencies in attached communities under the above heavy metal stresses. Transconjugants under Pb, As and Hg stresses were isolated and phylogenetically described. For As and Hg, the dominant genus was Pseudomonas, accounting for 88% and 96%, respectively. While under Pb stress, the genera Aeromonas and Enterobacter were the main transconjugants, accounting for 56% and 32% respectively. Moreover, ABC transporters and Amino acid metabolism, which were related to heavy metal transport and cellular metabolism, were dominant in the prediction of microbial metabolic function of transconjugants. This study can be helpful for risk assessment and control of ARG spreading in WWTPs.201931425984
7303170.9998Stepwise impact of urban wastewater treatment on the bacterial community structure, antibiotic contents, and prevalence of antimicrobial resistance. Bacteria, antibiotics, and antibiotic resistance determinants are key biological pollutants in aquatic systems, which may lead to bacterial infections or prevent the cure of bacterial infections. In this study, we investigated how the wastewater treatment processes in wastewater treatment plants (WWTPs) affect these pollutants. We found that the addition of oxygen, polyaluminum chloride (PAC), and polyacrylamide (PAM), as well as ultraviolet (UV) disinfection could significantly alter the bacterial communities in the water samples. An overall shift from Gram-negative bacteria to Gram-positive bacteria was observed throughout the wastewater treatment steps, but the overall bacterial biomass was not reduced in the WWTP samples. The antibiotic contents were reduced by the WWTP, but the size of the reduction and the step when antibiotic degradation occurred differed among antibiotics. Ciprofloxacin, sulfamethoxazole and erythromycin could be removed completely by the WWTP, whereas cephalexin could not. The removal of ciprofloxacin, cephalexin, and erythromycin occurred in the anaerobic digester, whereas the removal of sulfamethoxazole occurred after the addition of PAC and PAM, and UV disinfection. Antimicrobial resistance determinants were highly prevalent in all of the samples analyzed, except for those targeting vancomycin and colistin. However, wastewater treatment was ineffective at removing antimicrobial resistance determinants from wastewater. There were strong correlations between intI1, floR, sul1, and ermB, thereby suggesting the importance of integrons for the spread of these antimicrobial resistance genes. In general, this study comprised a stepwise analysis of the impact of WWTPs on three biological pollutants: bacteria, antibiotics, and antimicrobial resistance determinants, where our results suggest that the design of WWTPs needs to be improved to address the threats due to these pollutants.201728967569
7310180.9997Metagenomic Analysis Reveals Changes in Bacterial Communities and Antibiotic Resistance Genes in an Eye Specialty Hospital and a General Hospital Before and After Wastewater Treatment. The spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in hospital wastewater poses a great threat to public health, and wastewater treatment plants (WWTPs) play an important role in reducing the levels of ARB and ARGs. In this study, high-throughput metagenomic sequencing was used to analyze the bacterial community composition and ARGs in two hospitals exposed to different antibiotic use conditions (an eye specialty hospital and a general hospital) before and after wastewater treatment. The results showed that there were various potential pathogenic bacteria in the hospital wastewater, and the abundance and diversity of the influent ARGs in the general hospital were higher than those in the eye hospital. The influent of the eye hospital was mainly composed of Thauera and Pseudomonas, and sul1 (sulfonamide) was the most abundant ARG. The influent of the general hospital contained mainly Aeromonas and Acinetobacter, and tet39 (tetracycline) was the most abundant ARG. Furthermore, co-occurrence network analysis showed that the main bacteria carrying ARGs in hospital wastewater varied with hospital type; the same bacteria in wastewater from different hospitals could carry different ARGs, and the same ARG could also be carried by different bacteria. The changes in the bacterial community and ARG abundance in the effluent from the two hospitals showed that the activated sludge treatment and the direct chlorination disinfection can effectively remove some bacteria and ARGs in wastewater but have limitations. The species diversity increased significantly after the activated sludge treatment, while the direct chlorination disinfection did not increase the diversity. The activated sludge treatment has a better effect on the elimination of ARGs than the direct chlorination disinfection. In summary, we investigated the differences in bacterial communities and ARGs in wastewater from two hospitals exposed to different antibiotic usage conditions, evaluated the effects of different wastewater treatment methods on the bacterial communities and ARGs in hospital wastewater, and recommended appropriate methods for certain clinical environments.202235663906
7195190.9997Insight into effect of high-level cephalexin on fate and driver mechanism of antibiotics resistance genes in antibiotic wastewater treatment system. In the study, antibiotic resistance genes (ARGs) were examined in wastewater and sludge samples to explore the effect of cephalexin (CFX) on the spreading and removal of ARGs in the Expanded Granular Sludge Bed (EGSB) reactor treating antibiotics wastewater. The result showed that the addition of CFX in the wastewater affected the removal amount of β-lactam ARGs and other types ARGs. Besides, the addition of CFX in the wastewater had no obviously effect on total concentration of targeted ARGs in the sludge, but it was related to the accumulation of some typical ARGs. Based on gene cassette array libraries analysis, the diversity of gene cassettes carried by intI1 gene was increased by the addition of CFX in the wastewater. Furthermore, the co-occurrence patterns between ARGs and bacterial genus were also investigated. The results showed the CFX in the wastewater not only affected the number of potential host bacteria of ARGs, but also changed the types of potential host bacteria of ARGs. The correlation analysis of ARG in influent, effluent and sludge showed that, for blaCTX-M, sul2, qnrS and AmpC genes, their removal amount in EGSB reactor treating antibiotic wastewater system might be enhanced by reducing their concentration in the sludge.202032505047