# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 7298 | 0 | 1.0000 | Chronic exposure to triclosan sustains microbial community shifts and alters antibiotic resistance gene levels in anaerobic digesters. Triclosan, an antimicrobial chemical found in consumer personal care products, has been shown to stimulate antibiotic resistance in pathogenic bacteria. Although many studies focus on antibiotic resistance pertinent to medical scenarios, resistance developed in natural and engineered environments is less studied and has become an emerging concern for human health. In this study, the impacts of chronic triclosan (TCS) exposure on antibiotic resistance genes (ARGs) and microbial community structure were assessed in lab-scale anaerobic digesters. TCS concentrations from below detection to 2500 mg kg(-1) dry solids were amended into anaerobic digesters over 110 days and acclimated for >3 solid retention time values. Four steady state TCS concentrations were chosen (30-2500 mg kg(-1)). Relative abundance of mexB, a gene coding for a component of a multidrug efflux pump, was significantly higher in all TCS-amended digesters (30 mg kg(-1) or higher) relative to the control. TCS selected for bacteria carrying tet(L) and against those carrying erm(F) at concentrations which inhibited digester function; the pH decrease associated with digester failure was suspected to cause this selection. Little to no impact of TCS was observed on intI1 relative abundance. Microbial communities were also surveyed by high-throughput 16S rRNA gene sequencing. Compared to the control digesters, significant shifts in community structure towards clades containing commensal and pathogenic bacteria were observed in digesters containing TCS. Based on these results, TCS should be included in studies and risk assessments that attempt to elucidate relationships between chemical stressors (e.g. antibiotics), antibiotic resistance genes, and public health. | 2016 | 27291499 |
| 7299 | 1 | 0.9999 | Short-term exposure to benzalkonium chloride in bacteria from activated sludge alters the community diversity and the antibiotic resistance profile. The continuous introduction of cleaning products containing benzalkonium chloride (BAC) from household discharges can mold the microbial communities in wastewater treatment plants (WWTPs) in a way still poorly understood. In this study, we performed an in vitro exposure of activated sludge from a WWTP in Costa Rica to BAC, quantified the changes in intI1, sul2, and qacE/qacEΔ1 gene profiles, and determined alterations in the bacterial community composition. The analysis of the qPCR data revealed elevated charges of antibiotic resistance genes in the microbial community; after BAC's exposure, a significant increase in the qacE/qacEΔ1 gene, which is related to ammonium quaternary resistance, was observed. The 16S rRNA gene sequences' analysis showed pronounced variations in the structure of the bacterial communities, including reduction of the alpha diversity values and an increase of the relative abundance of Alphaproteobacteria, particularly of Rhodospseudomonas and Rhodobacter. We confirmed that the microbial communities presented high resilience to BAC at the mg/mL concentration, probably due to constant exposure to this pollutant. They also presented antibiotic resistance-related genes with similar mechanisms to tolerate this substance. These mechanisms should be explored more thoroughly, especially in the context of high use of disinfectant. | 2021 | 34874898 |
| 7202 | 2 | 0.9999 | Cyanobacterial extracellular antibacterial substances could promote the spread of antibiotic resistance: impacts and reasons. Many studies have shown that antibiotic resistance genes (ARGs) can be facilitated by a variety of antibacterial substances. Cyanobacteria are photosynthetic bacteria that are widely distributed in the ocean. Some extracellular substances produced by marine cyanobacteria have been found to possess antibacterial activity. However, the impact of these extracellular substances on ARGs is unclear. Therefore, we established groups of seawater microcosms that contained different concentrations (1000, 100, 10, 1, 0.1, 0.01, and 0 μg mL(-1)) of cyanobacterial extracellular substances (CES), and tracked the changes of 17 types of ARGs, the integron gene (intI1), as well as the bacterial community at different time points. The results showed that CES could enrich most ARGs (15/17) in the initial stage, particularly at low concentrations (10 and 100 μg mL(-1)). The correlation analysis showed a positive correlation between several ARGs and intI1. It is suggested that the abundance of intI1 increased with CES may contribute to the changes of these ARGs, and co-resistance of CES may be the underlying reason for the similar variation pattern of some ARGs. Moreover, the results of qPCR and high-throughput sequencing of 16S rRNA showed that CES had an inhibitory impact on the growth of bacterial communities. High concentrations of CES were found to alter the structure of bacterial communities. Co-occurrence networks showed that bacteria elevated in the high concentration group of CES and might serve as the potential hosts for a variety of ARGs. In general, marine cyanobacteria could play an important role in the global dissemination of ARGs and antibiotic-resistant bacteria (ARBs). | 2023 | 37947439 |
| 7190 | 3 | 0.9998 | Dynamics of microbial community and tetracycline resistance genes in biological nutrient removal process. The occurrence of antibiotics in wastewater has become a serious concern due to the possible development of antibiotic resistant bacteria in wastewater treatment process. In order to understand the dynamics of microbial community and tetracycline resistance genes in biological nutrient removal (BNR) process, three lab-scale sequencing batch reactors (SBRs) were operated under the stress of tetracycline. Results indicated that microbial community structure was altered, and tetracycline efflux pump genes were enhanced over 150-day operation in the presence of trace tetracycline of 20 and 50 μg L(-1), respectively. Furthermore, when the initial tetracycline concentrations were increased to 2 and 5 mg L(-1), substantial enhancement of tetracycline resistance was observed, accompanied with a sharp shift in microbial community structure. In this study, horizontal gene transfer was found to be the main mechanism for the development of tetracycline resistance genes under the long-terms stress of trace tetracycline. About 90.34% of the observed variations in tetracycline resistance genes could be explained by the dynamics of potential hosts of tetracycline resistance genes and class 1 integron. It should be noticed that the functional bacteria (e.g. Nitrospira, Dechloromonas, Rhodobacter and Candidatus_Accumulibacter) responsible for nutrient removal were positively correlated with tetracycline resistance, which might promote the prevalence of tetracycline resistance during biological wastewater treatment. Consequently, this study provided in-depth insights into the occurrence and prevalence of tetracycline resistance genes and their microbial hosts in BNR process. | 2019 | 30849601 |
| 7297 | 4 | 0.9998 | Reclaimed wastewater reuse in irrigation: Role of biofilms in the fate of antibiotics and spread of antimicrobial resistance. Reclaimed wastewater associated biofilms are made up from diverse class of microbial communities that are continuously exposed to antibiotic residues. The presence of antibiotic resistance bacteria (ARB) and their associated antibiotic resistance genes (ARGs) ensures also a continuous selection pressure on biofilms that could be seen as hotspots for antibiotic resistance dissemination but can also play a role in antibiotic degradation. In this study, the antibiotic degradation and the abundance of four ARGs (qnrS, sul1, blaTEM, ermB), and two mobile genetic elements (MGEs) including IS613 and intl1, were followed in reclaimed wastewater and biofilm samples collected at the beginning and after 2 weeks of six antibiotics exposure (10 µg L(-1)). Antibiotics were partially degraded and remained above lowest minimum inhibitory concentration (MIC) for environmental samples described in the literature. The most abundant genes detected both in biofilms and reclaimed wastewater were sul1, ermB, and intl1. The relative abundance of these genes in biofilms increased during the 2 weeks of exposure but the highest values were found in control samples (without antibiotics pressure), suggesting that bacterial community composition and diversity are the driven forces for resistance selection and propagation in biofilms, rather than exposure to antibiotics. Planktonic and biofilm bacterial communities were characterized. Planktonic cells are classically defined "as free flowing bacteria in suspension" as opposed to the sessile state (the so-called biofilm): "a structured community of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living. surface" as stated by Costerton et al. (1999). The abundance of some genera known to harbor ARG such as Streptococcus, Exiguobacterium, Acholeplasma, Methylophylaceae and Porphyromonadaceae increased in reclaimed wastewater containing antibiotics. The presence of biofilm lowered the level of these genera in wastewater but, at the opposite, could also serve as a reservoir of these bacteria to re-colonize low-diversity wastewater. It seems that maintaining a high diversity is important to limit the dissemination of antimicrobial resistance among planktonic bacteria. Antibiotics had no influence on the biofilm development monitored with optical coherence tomography (OCT). Further research is needed in order to clarify the role of inter-species communication in biofilm on antibiotic degradation and resistance development and spreading. | 2022 | 35841791 |
| 7201 | 5 | 0.9998 | Evolution 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. | 2019 | 30660087 |
| 7630 | 6 | 0.9998 | Coexistence of silver ion and tetracycline at environmentally relevant concentrations greatly enhanced antibiotic resistance gene development in activated sludge bioreactor. Antibiotic resistance has become a global public health problem. Recently, various environmental pollutants have been reported to induce the proliferation of antibiotic resistance. However, the impact of multiple pollutants (e.g., heavy metals and antibiotics), which more frequently occur in practical environments, is poorly understood. Herein, one widely distributed heavy metal (Ag(+)) and one frequently detected antibiotic (tetracycline) were chosen to investigate their coexisting effect on the proliferation of antibiotic resistance in the activated sludge system. Results show that the co-occurrence of Ag(+) and tetracycline at environmentally relevant concentrations exhibited no distinct inhibition in reactor performances. However, they inhibited the respiratory activity by 42%, destroyed the membrane structure by 218%, and increased membrane permeability by 29% compared with the blank control bioreactor. Moreover, the relative abundances of target antibiotic resistance genes (ARGs) (e.g., tetA, bla(TEM-1), and sulII) in effluent after exposure of coexisting Ag(+) and tetracycline were increased by 92-1983% compared with those in control reactor, which were 1.1-4.3 folds higher than the sum of the sole ones. These were possibly attributed to the enrichments of antibiotic-resistant bacteria. The results would illumine the coexisting effect of heavy metals and antibiotics on the dissemination of ARGs in activated sludge system. | 2022 | 34482077 |
| 7194 | 7 | 0.9998 | Response of antibiotic resistance genes in constructed wetlands during treatment of livestock wastewater with different exogenous inducers: Antibiotic and antibiotic-resistant bacteria. This work aimed to study the behavior of antibiotic resistance genes (ARGs) in constructed wetlands with different exogenous inducers additions (oxytetracycline and its resistant bacteria) by high-throughput quantitative polymerase chain reaction. Results indicated that constructed wetlands have the potential to reduce ARGs relative abundances in wastewater, and the total ARGs removal efficiency could exceed 60%. ARGs profile in the effluent differed from that in the influent, and that did not directly reflect the export of dominant ARGs in wetland biofilms. Meanwhile, the highest levels of detected numbers and relative abundances of ARGs were 43 and 3.35 × 10(-1) for control system and 44 and 6.40 × 10(-1) for treatment system, respectively, which meant that ARGs generation in wetlands were inevitable, and antibiotic and antibiotic-resistant bacteria from wastewater could indeed promote ARGs abundance in the system. Compared to the single roles of inducers, their synergistic role had a more significant influence on ARGs relative abundance. | 2020 | 32652450 |
| 7071 | 8 | 0.9998 | Impacts of multi-year field exposure of agricultural soil to macrolide antibiotics on the abundance of antibiotic resistance genes and selected mobile genetic elements. Exposure of environmental bacteria to antibiotics may be increasing the global resistome. Antibiotic residues are entrained into agricultural soil through the application of animal and human wastes, and irrigation with reclaimed water. The impact of a mixture of three macrolide antibiotics on the abundance of selected genes associated with antibiotic resistance and genetic mobility were determined in a long-term field experiment undertaken in London, Canada. Replicated plots received annual applications of a mixture of erythromycin, clarithromycin and azithromycin every spring since 2010. Each antibiotic was added directly to the soil at a concentration of either 0.1 or 10 mg kg soil(-1) and all plots were cropped to soybeans. By means of qPCR, no gene targets were enriched in soil exposed to the 0.1 mg kg soil(-1) dose compared to untreated control. In contrast, the relative abundance of several gene targets including int1, sul2 and mphE increased significantly with the annual exposure to the 10 mg kg soil(-1) dose. By means of high-throughput qPCR, numerous gene targets associated with resistance to aminoglycosides, sulfonamides, trimethoprim, streptomycin, quaternary ammonium chemicals as well as mobile genetic elements (tnpA, IS26 and IS6100) were detected in soil exposed to 10 mg kg soil(-1), but not the lower dose. Overall, exposure of soil to macrolide antibiotics increased the relative abundance of numerous gene targets associated with resistance to macrolides and other antibiotics, and mobile genetic elements. This occurred at an exposure dose that is unrealistically high, but did not occur at the lower more realistic exposure dose. | 2020 | 32330714 |
| 7068 | 9 | 0.9998 | Land application of sewage sludge: Response of soil microbial communities and potential spread of antibiotic resistance. The effect of land application of sewage sludge on soil microbial communities and the possible spread of antibiotic- and metal-resistant strains and resistance determinants were evaluated during a 720-day field experiment. Enzyme activities, the number of oligotrophic bacteria, the total number of bacteria (qPCR), functional diversity (BIOLOG) and genetic diversity (DGGE) were established. Antibiotic and metal resistance genes (ARGs, MRGs) were assessed, and the number of cultivable antibiotic- (ampicillin, tetracycline) and heavy metal- (Cd, Zn, Cu, Ni) resistant bacteria were monitored during the experiment. The application of 10 t ha(-1) of sewage sludge to soil did not increase the organic matter content and caused only a temporary increase in the number of bacteria, as well as in the functional and structural biodiversity. In contrast to expectations, a general adverse effect on the tested microbial parameters was observed in the fertilized soil. The field experiment revealed a significant reduction in the activities of alkaline and acid phosphatases, urease and nitrification potential. Although sewage sludge was identified as the source of several ARGs and MRGs, these genes were not detected in the fertilized soil. The obtained results indicate that the effect of fertilization based on the recommended dose of sewage sludge was not achieved. | 2021 | 33383416 |
| 7193 | 10 | 0.9998 | Plasmid-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. | 2025 | 39617560 |
| 7510 | 11 | 0.9998 | Impacts of antibiotics on biofilm bacterial community and disinfection performance on simulated drinking water supply pipe wall. Overuse of antibiotics is accelerating the spread of resistance risk in the environment. In drinking water supply systems, the effect of antibiotics on the resistance of biofilm is unclear, and there have been few studies in disinfectant-containing systems. Here, we designed a series of drinking water supply reactors to investigate the effects of antibiotics on biofilm and bacteria in the water. At low concentrations, antibiotics could promote the growth of bacteria in biofilm; among the tested antibiotics (tetracycline, sulfadiazine and chloramphenicol), tetracycline had the strongest ability to promote this. And the antibiotic resistant bacteria (ARB) could inhibit the growth of bacteria in drinking water. Results have shown that antibiotics enhanced the bacterial chlorine resistance in the effluent, but reduced that in the biofilm. Furthermore, metagenomic analysis showed that antibiotics reduced the richness of biofilm communities. The dominant phyla in the biofilm were Proteobacteria, Planctomycetes, and Firmicutes. In tetracycline-treated biofilm, the dominant phylum was Planctomycetes. In sulfadiazine- and chloramphenicol-treated groups, bacteria with complex cell structures preferentially accumulated. The dominant class in biofilm in the ARB-added group was Gammaproteobacteria. The abundance of antibiotic resistant genes (ARGs) was correlated with biofilm community structure. This study shows that antibiotics make the biofilm community structure of drinking water more resistant to chlorine. ARGs may be selective for certain bacteria in the process, and there may ultimately be enhanced chlorine and antibiotic resistance of effluent bacteria in drinking water. | 2021 | 34256291 |
| 7595 | 12 | 0.9998 | Performance and microbial community variations of anaerobic digesters under increasing tetracycline concentrations. The impact of different concentrations of tetracycline on the performance of anaerobic treatment was evaluated. Results revealed that for all of the tested tetracycline concentrations, no major sustained impact on methane production was observed. Instead, a significant increase in propionic acid was observed in the reactor subjected to the highest concentration of tetracycline (20 mg/L). Microbial community analyses suggest that an alternative methanogenic pathway, specifically that of methanol-utilizing methanogens, may be important for ensuring the stability of methane production in the presence of high tetracycline concentrations. In addition, the accumulation of propionate was due to an increase in volatile fatty acids (VFA)-producing bacteria coupled with a reduction in propionate utilizers. An increase in the abundance of tetracycline resistance genes associated with ribosomal protection proteins was observed after 30 days of exposure to high concentrations of tetracycline, while other targeted resistance genes showed no significant changes. These findings suggest that anaerobic treatment processes can robustly treat wastewater with varying concentrations of antibiotics while also deriving value-added products and minimizing the dissemination of associated antibiotic resistance genes. | 2017 | 28365798 |
| 6948 | 13 | 0.9998 | Fate of antibiotic resistance genes and metal resistance genes during the thermophilic fermentation of solid and liquid swine manures in an ectopic fermentation system. Environmental pollution due to resistance genes from livestock manure has become a serious issue that needs to be resolved. However, little studies focused on the removal of resistance genes in simultaneous processing of livestock feces and urine. This study investigated the fate of antibiotic resistance genes (ARGs), metal resistance genes (MRGs), and class 1 integron-integrase gene (intI1) during thermophilic fermentation of swine manure in an ectopic fermentation system (EFS), which has been regarded as a novel system for efficiently treating both feces and urine. The abundances of MRGs and tetracycline resistance genes were 34.44-97.71% lower in the EFS. The supplementation of heavy metals significantly increased the abundance of intI1, with the enhancement effect of copper being more prominent than that of zinc. The highest abundances of resistance genes and intI1 were observed at high Cu levels (A2), indicating that Cu can increase the spreading of resistance genes through integrons. Network analysis revealed the co-occurrence of ARGs, MRGs, and intI1, and these genes potentially shared the same host bacteria. Redundancy analysis showed that the bacterial community explained most of the variations in ARGs, and environmental factors had influences on ARGs abundances by modulating the bacterial community composition. The decreased Sphingomonas, Comamonas, Acinetobacter, Lactobacillus, Bartonella, Rhizobium, and Bacteroides were mainly responsible for the reduced resistance genes. These results demonstrate that EFS can reduce resistance genes in simultaneous processing of livestock feces and urine. | 2021 | 33592372 |
| 7191 | 14 | 0.9998 | The impact of antimicrobials on the efficiency of methane fermentation of sewage sludge, changes in microbial biodiversity and the spread of antibiotic resistance. The study was designed to simultaneously evaluate the influence of high doses (512-1024 µg/g) the most commonly prescribed antimicrobials on the efficiency of anaerobic digestion of sewage sludge, qualitative and quantitative changes in microbial consortia responsible for the fermentation process, the presence of methanogenic microorganisms, and the fate of antibiotic resistance genes (ARGs). The efficiency of antibiotic degradation during anaerobic treatment was also determined. Metronidazole, amoxicillin and ciprofloxacin exerted the greatest effect on methane fermentation by decreasing its efficiency. Metronidazole, amoxicillin, cefuroxime and sulfamethoxazole were degraded in 100%, whereas ciprofloxacin and nalidixic acid were least susceptible to degradation. The most extensive changes in the structure of digestate microbiota were observed in sewage sludge exposed to metronidazole, where a decrease in the percentage of bacteria of the phylum Bacteroidetes led to an increase in the proportions of bacteria of the phyla Firmicutes and Proteobacteria. The results of the analysis examining changes in the concentration of the functional methanogen gene (mcrA) did not reflect the actual efficiency of methane fermentation. In sewage sludge exposed to antimicrobials, a significant increase was noted in the concentrations of β-lactam, tetracycline and fluoroquinolone ARGs and integrase genes, but selective pressure was not specific to the corresponding ARGs. | 2021 | 33831706 |
| 3432 | 15 | 0.9998 | Insights into the amplification of bacterial resistance to erythromycin in activated sludge. Wastewater treatment plants are significant reservoirs for antimicrobial resistance. However, little is known about wastewater treatment effects on the variation of antibiotic resistance. The shifts of bacterial resistance to erythromycin, a macrolide widely used in human medicine, on a lab-scale activated sludge system fed with real wastewater was investigated from levels of bacteria, community and genes, in this study. The resistance variation of total heterotrophic bacteria was studied during the biological treatment process, based on culture dependent method. The alterations of bacterial community resistant to erythromycin and nine typical erythromycin resistance genes were explored with molecular approaches, including high-throughput sequencing and quantitative polymerase chain reaction. The results revealed that the total heterotrophs tolerance level to erythromycin concentrations (higher than 32 mg/L) was significantly amplified during the activated sludge treatment, with the prevalence increased from 9.6% to 21.8%. High-throughput sequencing results demonstrated an obvious increase of the total heterotrophic bacterial diversity resistant to erythromycin. Proteobacteria and Bacteroidetes were the two dominant phyla in the influent and effluent of the bioreactor. However, the prevalence of Proteobacteria decreased from 76% to 59% while the total phyla number increased greatly from 18 to 29 through activated sludge treatment. The gene proportions of erm(A), mef(E) and erm(D) were greatly amplified after biological treatment. It is proposed that the transfer of antibiotic resistance genes through the variable mixtures of bacteria in the activated sludge might be the reason for the antibiotic resistance amplification. The amplified risk of antibiotic resistance in wastewater treatment needs to be paid more attention. | 2015 | 25957255 |
| 7264 | 16 | 0.9998 | Dynamics of antibiotic resistance genes and presence of putative pathogens during ambient temperature anaerobic digestion. AIMS: This study was focused on evaluating the persistency of antimicrobial resistance (AR) genes and putative pathogenic bacteria in an anaerobic digesters operating at mesophilic ambient temperature, in two different year seasons: summer and winter. METHODS AND RESULTS: Abundance and dynamic of AR genes encoding resistance to macrolides (ermB), aminoglycosides (aphA2) and beta-lactams (blaTEM -1 ) and persistency of potentially pathogenic bacteria in pilot-scale anaerobic digesters were investigated. AR genes were determined in the influent and effluent in both conditions. Overall, after 60 days, reduction was observed for all evaluated genes. However, during the summer, anaerobic digestion was more related to the gene reduction as compared to winter. Persistency of potentially pathogenic bacteria was also evaluated by metagenomic analyses compared to an in-house created database. Clostridium, Acinetobacter and Stenotrophomonas were the most identified. CONCLUSIONS: Overall, considering the mesophilic ambient temperature during anaerobic digestion (summer and winter), a decrease in pathogenic bacteria detection through metagenomic analysis and AR genes is reported. Although the mesophilic anaerobic digestion has been efficient, the results may suggest medically important bacteria and AR genes persistency during the process. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report to show AR gene dynamics and persistency of potentially pathogenic bacteria through metagenomic approach in cattle manure ambient temperature anaerobic digestion. | 2014 | 25250562 |
| 7594 | 17 | 0.9998 | The impacts of triclosan on anaerobic community structures, function, and antimicrobial resistance. Triclosan is a widespread antimicrobial agent that accumulates in anaerobic digesters used to treat the residual solids generated at municipal wastewater treatment plants; there is very little information, however, about how triclosan impacts microbial communities in anaerobic digesters. We investigated how triclosan impacts the community structure, function and antimicrobial resistance genes in lab-scale anaerobic digesters. Previously exposed (to triclosan) communities were amended with 5, 50, and 500 mg/kg of triclosan, corresponding to the median, 95th percentile, and 4-fold higher than maximum triclosan concentration that has been detected in U.S. biosolids. Triclosan amendment caused all of the Bacteria and Archaea communities to structurally diverge from that of the control cultures (based on ARISA). At the end of the experiment, all triclosan-amended Archaea communities had diverged from the control communities, regardless of the triclosan concentration added. In contrast, over time the Bacteria communities that were amended with lower concentrations of triclosan (5 mg/kg and 50 mg/kg) initially diverged and then reconverged with the control community structure. Methane production at 500 mg/kg was nearly half the methane production in control cultures. At 50 mg/kg, a large variability in methane production was observed, suggesting that 50 mg/kg may be a tipping point where function begins to fail in some communities. When previously unexposed communities were exposed to 500 mg triclosan/kg, function was maintained, but the abundance of a gene encoding for triclosan resistance (mexB) increased. This research suggests that triclosan could inhibit methane production in anaerobic digesters if concentrations were to increase and may also select for resistant Bacteria. In both cases, microbial community composition and exposure history alter the influence of triclosan. | 2014 | 24915110 |
| 7511 | 18 | 0.9998 | Antibiotic resistome promotion in drinking water during biological activated carbon treatment: Is it influenced by quorum sensing? The contamination of antibiotic resistance genes (ARGs) in drinking water may pose a direct threat to human health. This study applied high-throughput qPCR and sequencing to investigate the dynamics of ARGs and bacterial communities during the advanced treatment of drinking water using biological activated carbon. The promotion of ARGs was observed, and the normalized copy number of ARGs increased significantly after BAC treatment, raising the number of detected ARGs from 84 to 159. Twenty-nine ARGs were identified as biofilm-influencing sources in the BAC, and they persisted after chlorination. The shift of bacterial communities primarily had effects on the changes in resistome. Firmicutes, Cyanobacteria were related to persistent ARGs mostly in the BAC biofilm. Meanwhile, the Acyl-Homoserine Lactones (AHLs), quorum sensing molecules, and bacteria that produced AHLs were identified to understand the promotion of ARGs. The isolated AHL-producing bacteria belonged to the Proteobacteria, Firmicutes and Bacteroidetes phyla. Six detectable AHLs had an influence on plasmid-based horizontal gene transfer in the intragenus mating systems, indicating that the dynamics of ARGs were strongly affected by quorum sensing between specific bacteria in the biofilm. These results provide new insight into the mechanism of antibiotic resistome promotion in BAC biofilms. | 2018 | 28846900 |
| 7199 | 19 | 0.9998 | Minimum influent concentrations of oxytetracycline, streptomycin and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems. It has been demonstrated that antibiotic resistance could be induced and selected under high antibiotic concentrations in biological wastewater treatment systems. However, little is available regarding the minimum concentrations of antibiotics for selecting antibiotic resistance during wastewater treatment. Herein, the minimum influent concentrations of oxytetracycline, streptomycin, and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems were investigated by spiking respective antibiotic into wastewater with an antibiotic dose increasing from 0 to 0.1, 1, 5, 25, 50 mg/L stepwise over a period of 606 days. Significant increase (p < .01) in the total abundance of antibiotic resistance genes was observed for both streptomycin and oxytetracycline at a dose of 0.1 mg/L according to metagenomic sequencing, while the concentration levels leading to significant increases (p < .05) in resistant bacteria ratio were higher: 5 mg/L for streptomycin and 25 mg/L for oxytetracycline. Although resistome abundance increased with the increase of spiramycin dose, neither the corresponding Macrolide-Lincosamide-Streptogramin (MLS) resistance genes nor the resistant bacteria ratio showed perceptible increase. Partial canonical correspondence analysis showed that both bacterial community shift and mobile genetic elements alteration contributed to the enrichment of resistomes under the presence of streptomycin and oxytetracycline. Regarding spiramycin which is mainly targeting on Gram-positive bacteria, the dominance of the intrinsically resisting Gram-negative bacteria in the biofilm microbiota might be responsible for the vague change of MLS resistant determinants under the spiramycin stress. The results demonstrated that it is possible to prevent the development of antibiotic resistance during wastewater treatment by controlling the influent streptomycin and oxytetracyline concentrations below 0.1 mg/L. This work proposed an actionable approach for the management of antibiotic production wastewater. | 2020 | 32325576 |