Ultraviolet reduction of erythromycin and tetracycline resistant heterotrophic bacteria and their resistance genes in municipal wastewater. - Related Documents




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777601.0000Ultraviolet reduction of erythromycin and tetracycline resistant heterotrophic bacteria and their resistance genes in municipal wastewater. Antibiotic resistance in wastewater is becoming a major public health concern, but poorly understood about impact of disinfection on antibiotic resistant bacteria and antibiotic resistance genes. The UV disinfection of antibiotic resistant heterotrophic bacteria and their relevant genes in the wastewater of a municipal wastewater treatment plant has been evaluated. Two commonly used antibiotics, erythromycin and tetracycline were selected because of their wide occurrences in regard to the antibiotic resistance problem. After UV treatment at a fluence of 5mJcm(-2), the log reductions of heterotrophic bacteria resistant to erythromycin and tetracycline in the wastewater were found to be 1.4±0.1 and 1.1±0.1, respectively. The proportion of tetracycline-resistant bacteria (5%) was nearly double of that before UV disinfection (3%). Tetracycline-resistant bacteria exhibited more tolerance to UV irradiation compared to the erythromycin-resistant bacteria (p<0.05). Gene copy numbers were quantified via qPCR and normalized to the volume of original sample. The total concentrations of erythromycin- and tetracycline-resistance genes were (3.6±0.2)×10(5) and (2.5±0.1)×10(5) copies L(-1), respectively. UV treatment at a fluence of 5mJcm(-2) removed the total erythromycin- and tetracycline-resistance genes by 3.0±0.1 log and 1.9±0.1 log, respectively. UV treatment was effective in reducing antibiotic resistance in the wastewater.201324055024
777810.9998Distribution of antibiotic resistance in the effluents of ten municipal wastewater treatment plants in China and the effect of treatment processes. Municipal wastewater treatment plant (WWTP) effluents represent an important contamination source of antibiotic resistance, threatening the ecological safety of receiving environments. In this study, the release of antibiotic resistance to sulfonamides and tetracyclines in the effluents of ten WWTPs in China was investigated. Results indicate that the concentrations of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) ranged from 1.1 × 10(1) to 8.9 × 10(3) CFU mL(-1) and 3.6 × 10(1) (tetW) to 5.4 × 10(6) (tetX) copies mL(-1), respectively. There were insignificant correlations of the concentrations of ARB and ARGs with those of corresponding antibiotics. Strong correlations were observed between the total concentrations of tetracycline resistance genes and sulfonamide resistance genes, and both of which were significantly correlated with intI1 concentrations. Statistical analysis of the effluent ARG concentrations in different WWTPs revealed an important role of disinfection in eliminating antibiotic resistance. The release rates of ARB and ARGs through the effluents of ten WWTPs ranged from 5.9 × 10(12) to 4.8 × 10(15) CFU d(-1) and 6.4 × 10(12) (tetW) to 1.7 × 10(18) (sul1) copies d(-1), respectively. This study helps the effective assessment and scientific management of ecological risks induced by antibiotic resistance discharged from WWTPs.201728088530
777420.9998Antibiotic-resistant genes and antibiotic-resistant bacteria in the effluent of urban residential areas, hospitals, and a municipal wastewater treatment plant system. In this study, we determined the abundance of 8 antibiotics (3 tetracyclines, 4 sulfonamides, and 1 trimethoprim), 12 antibiotic-resistant genes (10 tet, 2 sul), 4 antibiotic-resistant bacteria (tetracycline, sulfamethoxazole, and combined resistance), and class 1 integron integrase gene (intI1) in the effluent of residential areas, hospitals, and municipal wastewater treatment plant (WWTP) systems. The concentrations of total/individual targets (antibiotics, genes, and bacteria) varied remarkably among different samples, but the hospital samples generally had a lower abundance than the residential area samples. The WWTP demonstrated removal efficiencies of 50.8% tetracyclines, 66.8% sulfonamides, 0.5 logs to 2.5 logs tet genes, and less than 1 log of sul and intI1 genes, as well as 0.5 log to 1 log removal for target bacteria. Except for the total tetracycline concentration and the proportion of tetracycline-resistant bacteria (R (2) = 0.330, P < 0.05), there was no significant correlation between antibiotics and the corresponding resistant bacteria (P > 0.05). In contrast, various relationships were identified between antibiotics and antibiotic resistance genes (P < 0.05). Tet (A) and tet (B) displayed noticeable relationships with both tetracycline and combined antibiotic-resistant bacteria (P < 0.01).201525323405
777730.9998Fate of antibiotic resistant cultivable heterotrophic bacteria and antibiotic resistance genes in wastewater treatment processes. Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are emerging contaminants of environmental concern. Heterotrophic bacteria in activated sludge have an important role in wastewater treatment plants (WWTPs). However, the fate of cultivable heterotrophic ARB and ARGs in WWPTs process remains unclear. In the present study, we investigated the antibiotic-resistant phenotypes of cultivable heterotrophic bacteria from influent and effluent water of three WWTPs and analysed thirteen ARGs in ARB and in activated sludge from anoxic, anaerobic and aerobic compartments. From each influent or effluent sample of the three plants, 200 isolates were randomly tested for susceptibility to 12 antibiotics. In these samples, between 5% and 64% isolates showed resistance to >9 antibiotics and the proportion of >9-drug-resistant bacteria was lower in isolates from effluent than from influent. Eighteen genera were identified in 188 isolates from influent (n=94) and effluent (n=94) of one WWTP. Six genera (Aeromonas, Bacillus, Lysinibacillus, Microbacterium, Providencia, and Staphylococcus) were detected in both influent and effluent samples. Gram-negative and -positive isolates dominated in influent and effluent, respectively. The 13 tetracycline-, sulphonamide-, streptomycin- and β-lactam-resistance genes were detected at a higher frequency in ARB from influent than from effluent, except for sulA and CTX-M, while in general, the abundances of ARGs in activated sludge from two of the three plants were higher in aerobic compartments than in anoxic ones, indicating abundant ARGs exit in the excess sledges and/or in uncultivable bacteria. These findings may be useful for elucidating the effect of WWTP on ARB and ARGs.201525950407
533540.9998Quantification of vancomycin-resistant enterococci and corresponding resistance genes in a sewage treatment plant. This study aimed to analyze vancomycin-resistant enterococci (VRE) and their resistance genes, vanA and vanB, to examine their presence in sewage treatment systems. Water samples were collected from primary sedimentation tank inlet, aeration tank, final sedimentation tank overflow outlet, and disinfection tank. Enterococcal strains were determined their vancomycin susceptibility by the minimum inhibitory concentration (MIC) test. Vancomycin-resistance genes (vanA and vanB) were quantified by real-time PCR. The sewage treatment process indeed decreased the number of most enterococci contained in the entering sewage, with a removal rate of ≥ 5 log. The MIC test showed that two enterococcal strains resistant to a high concentration of vancomycin (>128 μg mL(-1)). However, most of the enterococcal strains exhibited sensitivity to vancomycin, indicating that VRE were virtually absent in the sewage treatment systems. On the other hand, vancomycin-resistance genes were detected in all the sewage samples, including those collected from the chlorination disinfection tank. The highest copy numbers of vanA (1.5 × 10(3) copies mL(-1)) and vanB (1.0 × 10(3) copies mL(-1)) were detected from the water sample of effluent water and chlorinated water, respectively. Therefore, antibiotic resistance genes remain in the sewage treatment plant and might discharged into water environments such as rivers and coastal areas.201526121014
779450.9998Fate of antibiotic resistant bacteria and genes during wastewater chlorination: implication for antibiotic resistance control. This study investigated fates of nine antibiotic-resistant bacteria as well as two series of antibiotic resistance genes in wastewater treated by various doses of chlorine (0, 15, 30, 60, 150 and 300 mg Cl2 min/L). The results indicated that chlorination was effective in inactivating antibiotic-resistant bacteria. Most bacteria were inactivated completely at the lowest dose (15 mg Cl2 min/L). By comparison, sulfadiazine- and erythromycin-resistant bacteria exhibited tolerance to low chlorine dose (up to 60 mg Cl2 min/L). However, quantitative real-time PCRs revealed that chlorination decreased limited erythromycin or tetracycline resistance genes, with the removal levels of overall erythromycin and tetracycline resistance genes at 0.42 ± 0.12 log and 0.10 ± 0.02 log, respectively. About 40% of erythromycin-resistance genes and 80% of tetracycline resistance genes could not be removed by chlorination. Chlorination was considered not effective in controlling antimicrobial resistance. More concern needs to be paid to the potential risk of antibiotic resistance genes in the wastewater after chlorination.201525738838
533160.9998Performance evaluation of ozonation for removal of antibiotic-resistant Escherichia coli and Pseudomonas aeruginosa and genes from hospital wastewater. The performance of ozonation for the removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) using Escherichia coli and Pseudomonas aeruginosa carrying ARGs from hospital wastewaters was evaluated in this study. Bacterial inactivation was determined using plate count methods and real time PCR for ARG damage (Sul1, bla(tem), bla(ctx), bla(vim) and qnrS). The reduction rate of bacterial cells and ARGs was increased by different amounts of transferred ozone dose from 11 to 45 mg/L. The concentration of 10(8) cfu/ml bacteria was reduced  to an acceptable level by ozone treatment after a 5 min contact time,  Although the removal rate was much higher for concentrations of 10(6) cfu/ml and 10(4) cfu/ml bacteria. Overall, the tendency of gene reduction by ozonation from more to less was 16S rRNA > sul1 > bla(tem) > bla(ctx) > qnrS > bla(vim). Given that plasmid-borne ARGs can potentially be transferred to other bacteria even after the disinfection process, our results can provide important insights into the fate of ARGs during hospital wastewater ozonation.202134972828
718270.9998Effects of UV disinfection on phenotypes and genotypes of antibiotic-resistant bacteria in secondary effluent from a municipal wastewater treatment plant. To elucidate the effects of UV disinfection on antibiotic resistance in biologically-treated wastewater, we investigated the antibiotic resistance profiles, species of cultivable heterotrophic bacteria, and antibiotic-resistance genes (ARGs) in antibiotic-resistant bacteria before and after treatment. UV disinfection greatly changed the bacterial community structure and the antibiotic resistance in wastewater. The antibiotic resistance in wastewater samples was strongly associated with the bacterial community. The proportions of Gram-positive bacteria gradually increased with increasing UV fluence. The proportions of bacteria resistant to cephalexin, penicillin, and vancomycin all greatly decreased after UV treatment in both sampling events (July 2018 and January 2019), and those for bacteria resistant to ofloxacin, ciprofloxacin, and sulfadiazine increased, resulting from the alternative antibiotic resistance profiles among different genera. UV disinfection induced the selection of multi-antibiotic resistant (MAR) bacteria. For example, the MAR indices of Aeromonas, the dominant genus during the treatments, were significantly increased after UV irradiation (P < 0.05). The MAR index was also markedly increased (P < 0.05) at a fluence of 5 mJ/cm(2) in both events. In UV10 treatment, the bacterial community structure was greatly changed. The genera with relatively low MAR indices replaced that with high MAR indices, and became the dominant genera. As a result, the MAR indices of treated samples showed a decreased trend after 10 mJ/cm(2) UV irradiation. The detection frequencies of ARGs located on the chromosome varied mainly due to the evolution of the microbial community. The occurrence of ARGs (tetA, tetC, tetM, tetW, tetX, and sul1) located on plasmid DNA decreased after UV disinfection, and the average detection frequencies of tet and sul genes decreased by 15% and 6%, respectively (P < 0.05). Generally speaking, the effect of UV disinfection on the enrichment of antibiotic resistance is limited in this study, and horizontal gene transfer via the plasmids in surviving bacteria might be impaired due to the decreased abundance of ARGs on the plasmids.201930991178
532480.9998Abundances of tetracycline, sulphonamide and beta-lactam antibiotic resistance genes in conventional wastewater treatment plants (WWTPs) with different waste load. Antibiotics and antibiotic resistant bacteria enter wastewater treatment plants (WWTPs), an environment where resistance genes can potentially spread and exchange between microbes. Several antibiotic resistance genes (ARGs) were quantified using qPCR in three WWTPs of decreasing capacity located in Helsinki, Tallinn, and Tartu, respectively: sulphonamide resistance genes (sul1 and sul2), tetracycline resistance genes (tetM and tetC), and resistance genes for extended spectrum beta-lactams (blaoxa-58, blashv-34, and blactx-m-32). To avoid inconsistencies among qPCR assays we normalised the ARG abundances with 16S rRNA gene abundances while assessing if the respective genes increased or decreased during treatment. ARGs were detected in most samples; sul1, sul2, and tetM were detected in all samples. Statistically significant differences (adjusted p<0.01) between the inflow and effluent were detected in only four cases. Effluent values for blaoxa-58 and tetC decreased in the two larger plants while tetM decreased in the medium-sized plant. Only blashv-34 increased in the effluent from the medium-sized plant. In all other cases the purification process caused no significant change in the relative abundance of resistance genes, while the raw abundances fell by several orders of magnitude. Standard water quality variables (biological oxygen demand, total phosphorus and nitrogen, etc.) were weakly related or unrelated to the relative abundance of resistance genes. Based on our results we conclude that there is neither considerable enrichment nor purification of antibiotic resistance genes in studied conventional WWTPs.201425084517
776790.9998Degradation of plasmid-mediated resistance genes in poultry slaughterhouse wastewater employing a UV/H(2)O(2) process: A metagenomic approach. Poultry slaughterhouse effluents are important hotspots for the spread of both antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs), contributing to the antimicrobial resistance (AMR). This study reports a novel investigation to assess the effects of UV/H(2)O(2) treatment on the removal of metaplasmidome-mediated ARGs from poultry slaughterhouse effluents. The effluent samples were subjected at 0.005-0.15 mol L(-1) of H(2)O(2) and pH conditions (3, 5, 7 and 9). Bacterial community (rrs 16S rRNA), Escherichia coli (uidA) antimicrobial resistance (sul1 and int1) and metagenomic plasmid DNA removal were assessed. The UV/H(2)O(2) treatment employing H(2)O(2) = 0.01 mol L(-1) at pH 3 resulted in decreased of several markers (uidA, sul1 and int1). A metaplasmidome indicated the persistence of Burkholderiales order. The UV/H(2)O(2) process reduced plasmid-associated ARGs by 92.5% and 90.4% at pH 3 and 7, respectively. Persistent genes were mainly composed of genes associated with efflux pumps and resistance to beta-lactams and fluoroquinolones. These findings contribute to mitigate the spread of AMR in the agricultural sector, especially through the implementation of more efficient treatments, and reducing the use of antibiotics in livestock farming.202539826254
5323100.9998Monitoring and assessing the impact of wastewater treatment on release of both antibiotic-resistant bacteria and their typical genes in a Chinese municipal wastewater treatment plant. Wastewater treatment plants (WWTPs) are important hotspots for the spread of antibiotic resistance. However, the release and impact factors of both antibiotic resistant bacteria and the relevant genes over long periods in WWTPs have rarely been investigated. In this study, the fate of bacteria and genes resistant to six commonly used antibiotics was assessed over a whole year. In WWTP effluent and biosolids, a high prevalence of heterotrophic bacteria resistant to vancomycin, cephalexin, sulfadiazine and erythromycin were detected, each with a proportion of over 30%. The corresponding genes (vanA, ampC, sulI and ereA) were all detected in proportions of (2.2 ± 0.8) × 10(-10), (6.2 ± 3.2) × 10(-9), (1.2 ± 0.8) × 10(-7) and (7.6 ± 4.8) × 10(-8), respectively, in the effluent. The sampling season imposed considerable influence on the release of all ARB. High release loads of most ARB were detected in the spring, while low release loads were generally found in the winter. In comparison, the ARG loads changed only slightly over various seasons. No statistical relevance was found between all ARB abundances and their corresponding genes over the long-term investigation period. This inconsistent behavior indicates that bacteria and genes should both be considered when exploring resistance characteristics in wastewater. A redundancy analysis was adopted to assess the impact of wastewater quality and operational conditions on antibiotic resistance. The results indicated that most ARB and ARG proportions were positively related to the COD and turbidity of the raw sewage, while negatively related to those of the effluent. DO and temperature exhibited strong negative relevance to most ARB prevalence.201424927359
5336110.9998Resistant Genes and Multidrug-Resistant Bacteria in Wastewater: A Study of Their Transfer to the Water Reservoir in the Czech Republic. Wastewater is considered the most serious source of the spread of antibiotic resistance in the environment. This work, therefore, focuses on the fate and spread of antibiotic resistance genes (ARGs) in wastewater and the monitoring of multidrug-resistant strains. ARGs were monitored in the nitrification and sedimentation tanks of the wastewater treatment plant (WWTP) and in the dam into which this WWTP flows, at various times. The highest relative abundance was found for the blaTEM > tetW > blaNDM-1 > vanA resistance genes, respectively. An increased concentration of tetracycline (up to 96.00 ng/L) and ampicillin (up to 19.00 ng/L) was found in water samples compared to other antibiotics detected. The increased incidence of seven ARGs and four antibiotics was observed in the November and December sampling times. Isolated ampicillin-resistant strains showed a high degree of resistance to ampicillin (61.2% of the total isolates had a minimum inhibitory concentration (MIC) ≥ 20 mg/mL). In 87.8% of isolates, out of the total number, the occurrence of two or more ARGs was confirmed. These multidrug-resistant strains were most often identified as Aeromonas sp. This strain could represent a significant role in the spread of multidrug resistance through wastewater in the environment.202235207435
3520120.9998Influence of tetracycline on tetracycline-resistant heterotrophs and tet genes in activated sludge process. The concentrations of tetracycline-intermediate resistant, tetracycline-resistant heterotrophic bacteria, and total heterotrophic bacteria were examined to assess the influence of tetracycline on tetracycline-resistant heterotrophs by the R2A agar cultivation method in the tetracycline fortified activated sludge process and in the natural background. Results showed that the percentages of both tetracycline-intermediate resistant and tetracycline-resistant heterotrophic bacteria in total heterotrophic bacteria were significantly increased, after tetracycline was fed to activated sludge for a 3 months period under four different operating conditions, as compared with the background. In order to investigate the mechanism of activated sludge resistance to tetracycline, polymerase chain reaction experiments were carried out to analyze the existence and evolution of tet genes in the presence of tetracycline. Results revealed that only tet A and tet B genes out of the 11 target tet genes were observed in tetracycline treated activated sludge while no tet gene was detected in background. This indicated that tet A gene could accumulate in activated sludge with slower and continuous influent, while the accumulation of tet B gene could be attributed to shorter hydraulic retention time. Therefore, it was proposed in this study that tetracycline-resistant genes created by efflux pumps spread earlier and quicker to encode resistance to tetracycline, which facilitated the increase in tetracycline-resistance.201525424345
7180130.9998Removal of antibiotic residues, antibiotic resistant bacteria and antibiotic resistance genes in municipal wastewater by membrane bioreactor systems. Antibiotic residues, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are considered new classes of water contaminants due to their potential adverse effects on aquatic ecosystems and human health. This paper provides comprehensive data on the occurrences of 19 antibiotics, bacteria resistant to 10 antibiotics, and 15 ARGs in raw influent and different treatment stages of conventional activated sludge (CAS) and membrane bioreactor (MBR) systems. Seventeen out of the 19 target antibiotics were detected in raw influent with concentrations of up to ten micrograms per liter. Concentrations of antibiotics measured in the secondary effluent were much lower compared to those in the raw influent. Among the antibiotics, amoxicillin, azithromycin, ciprofloxacin, chloramphenicol, meropenem, minocycline, oxytetracycline, sulfamethazine and vancomycin had highest removal by CAS or MBR systems with median removal efficiency (RE) > 70%, while trimethoprim and lincomycin were recalcitrant in the CAS system with median RE <50%. Similarly, the target ARB and ARGs were omnipresent in the raw influent samples with average concentrations as high as 2.6 × 10(6) CFU/mL and 2.0 × 10(7) gene copies/mL, respectively. The concentrations of ARB in secondary effluent of the CAS system declined relative to the raw influent (i.e. lower than raw influent by 2-3 orders of magnitude) and no ARB were detected in the MF permeate of the MBR system. For ARGs, their concentrations in secondary effluent/MF permeate ranged from below method quantification limit (201830193193
7771140.9998Can chlorination co-select antibiotic-resistance genes? Selective pressures, such as chemical or heavy metal pollution, may co-select for bacterial antibiotic resistance in the environment. However, whether chlorination in water treatment can co-select antibiotic-resistant bacteria is controversial. In this study, high capacity quantitative polymerase chain reaction (qPCR) analysis was applied to target almost all known antibiotic-resistance genes (ARGs) (282 types) and 13 mobile genetic elements (MGEs) in bacteria detected in secondary effluents from a municipal wastewater treatment plant after chlorination. The results revealed that 125 unique ARGs were detected in non-chlorinated samples, and the number decreased (79-91 types) as the chlorine concentration was increased. Moreover, 7.49 × 10(4)-3.92 × 10(7) copies/100 ml water reduction of ARGs occurred with 4 mg Cl2/l. Considering the relative abundance of ARGs (i.e., ARG copies normalized to 16S rRNA gene copies), 119 ARGs decreased in response to chlorination, whereas only six ARGs, such as dfrA1, tetPB-03, tetPA, ampC-04, tetA-02, and erm(36), were potentially enriched by 10.90-, 10.06-, 8.63-, 6.86-, 3.77-, and 1.09-fold, respectively. Furthermore, the relative abundance of 12 detected MGEs was lower after chlorination. Therefore, chlorination was effective in reducing ARGs and MGEs rather than co-selecting them.201627192478
5306150.9998Occurrence of tetracycline-resistant fecal coliforms and their resistance genes in an urban river impacted by municipal wastewater treatment plant discharges. Antibiotic resistance of fecal coliforms in an urban river poses great threats to both human health and the environment. To investigate the occurrence and distribution of antibiotic resistant bacteria in an urban river, water samples were collected from the Chanhe River in Xi'an, China. After membrane filtration of water samples, the tetracycline resistance rate of fecal coliforms and their resistance genes were detected by plating and polymerase chain reaction (PCR), respectively. We found that fecal coliforms were generally resistant to tetracycline and saw average resistance rates of 44.7%. The genes tetA and tetB were widely detected, and their positive rate was 60%-100% and 40%-90%, respectively. We found few strains containing tetC, tetK, tetQ and tetX, and we did not identify any strains containing tetG, tetM or tetO. The prevalence of tetA and tetB over other genes indicated that the main mechanism for resistance to tetracycline is by changes to the efflux pump. Our analysis of the types and proportion of tetracycline resistance genes in the Chanhe River at locations upstream and downstream of the urban center suggests that the increased number of tetracycline-resistant fecal coliforms and spatial variation of tetracycline resistance genes diversity were related to municipal wastewater treatment plant discharge.201525901852
5325160.9998Genes encoding tetracycline resistance in a full-scale municipal wastewater treatment plant investigated during one year. Tetracycline-resistant bacteria and genes encoding tetracycline resistance are common in anthropogenic environments. We studied how wastewater treatment affects the prevalence and concentration of two genes, tetA and tetB, that encode resistance to tetracycline. Using real-time polymerase chain reaction (PCR) we analysed wastewater samples collected monthly for one year at eight key-sites in a full-scale municipal wastewater treatment plant (WWTP). We detected tetA and tetB at each sampling site and the concentration of both genes, expressed per wastewater volume or per total-DNA, decreased over the treatment process. The reduction of tetA and tetB was partly the result of the sedimentation process. The ratio of tetA and tetB, respectively, to total DNA was lower in or after the biological processes. Taken together our data show that tetracycline resistance genes occur throughout the WWTP, and that the concentrations are reduced under conventional operational strategies.201020154388
7094170.9998Prevalence of sulfonamide and tetracycline resistance genes in drinking water treatment plants in the Yangtze River Delta, China. The occurrence and distribution of antibiotic resistance genes (ARGs) in drinking water treatment plants (DWTPs) and finished water are not well understood, and even less is known about the contribution of each treatment process to resistance gene reduction. The prevalence of ten commonly detected sulfonamide and tetracycline resistance genes, namely, sul I, sul II, tet(C), tet(G), tet(X), tet(A), tet(B), tet(O), tet(M) and tet(W) as well as 16S-rRNA genes, were surveyed in seven DWTPs in the Yangtze River Delta, China, with SYBR Green I-based real-time quantitative polymerase chain reaction. All of the investigated ARGs were detected in the source waters of the seven DWTPs, and sul I, sul II, tet(C) and tet(G) were the four most abundant ARGs. Total concentrations of ARGs belonging to either the sulfonamide or tetracycline resistance gene class were above 10(5) copies/mL. The effects of a treatment process on ARG removal varied depending on the overall treatment scheme of the DWTP. With combinations of the treatment procedures, however, the copy numbers of resistance genes were reduced effectively, but the proportions of ARGs to bacteria numbers increased in several cases. Among the treatment processes, the biological treatment tanks might serve as reservoirs of ARGs. ARGs were found in finished water of two plants, imposing a potential risk to human health. The results presented in this study not only provide information for the management of antibiotics and ARGs but also facilitate improvement of drinking water quality.201424984233
5333180.9998Antibiotic resistance profile of wastewater treatment plants in Brazil reveals different patterns of resistance and multi resistant bacteria in final effluents. Wastewater treatment plants (WWTPs) are recognized as important sources of Antibiotic Resistant Bacteria (ARBs) and Antibiotic Resistant Genes (ARGs), and might play a role in the removal and dissemination of antimicrobial resistance (AMR) in the environment. Detailed information about AMR removal by the different treatment technologies commonly applied in urban WWTPs is needed. This study investigated the occurrence, removal and characterization of ARBs in WWTPs employing different technologies: WWTP-A (conventional activated sludge-CAS), WWTP-B (UASB reactor followed by biological trickling filter) and WWTP-C (modified activated sludge followed by UV disinfection-MAS/UV). Samples of raw sewage (RI) and treated effluent (TE) were collected and, through the cultivation-based method using 11 antibiotics, the antibiotic resistance profiles were characterized in a one-year period. MAS was effective in reducing ARB counts (2 to 3 log units), compared to CAS (1 log unit) and UASB/BTF (0.5 log unit). The composition of cultivable ARB differed between RI and TE samples. Escherichia was predominant in RI (56/118); whilst in TE Escherichia (31/118) was followed by Bacillus (22/118), Shigella (14/118) and Enterococcus (14/118). Most of the isolates identified (370/394) harboured at least two ARGs and in over 80 % of the isolates, 4 or more ARG (int1, blaTEM, TetA, sul1 and qnrB) were detected. A reduction in the resistance prevalence was observed in effluents after CAS and MAS processes; whilst a slight increase was observed in treated effluents from UASB/BTF and after UV disinfection stage. The multi-drug resistance (MDR) phenotype was attributed to 84.3 % of the isolates from RI (27/32) and 63.6 % from TE (21/33) samples and 52.3 % of the isolates (34/65) were resistant to carbapenems (imipenem, meropenem, ertapenem). The results indicate that treated effluents are still a source for MDR bacteria and ARGs dissemination to aquatic environments. The importance of biological sewage treatment was reinforced by the significant reductions in ARB counts observed. However, implementation of additional treatments is needed to mitigate MDR bacteria release into the environment.202336240935
5326190.9997The presence of antibiotic-resistant bacteria at four Norwegian wastewater treatment plants: seasonal and wastewater-source effects. Wastewater treatment plants receive low concentrations of antibiotics. Residual concentrations of antibiotics in the effluent may accelerate the development of antibiotic resistance in the receiving environments. Monitoring of antimicrobial resistance genes (ARGs) in countries with strict regulation of antibiotic use is important in gaining knowledge of how effective these policies are in preventing the emergence of ARGs or whether other strategies are required, for example, at-source treatment of hospital effluents. This study evaluates the presence of certain common resistance genes (bla (SHV-1), bla (TEM-1), msrA, ermA, ermC, tetM, tetL, tetA, vanA, and vanC) in the influent, sludge, and effluent of four wastewater treatment plants (WWTPs) in the North Jæren region of Norway at two different sampling times (January and May). These WWTPs vary in drainage area and wastewater composition and were selected based on their differing wastewater characteristics. Randomly selected colonies from the activated sludge samples were used to determine the minimum inhibitory concentration (MIC) for ampicillin, vancomycin, and tetracycline. In addition, variations in the bacterial composition of the wastewater were characterized via 16S rRNA sequencing and were analyzed in terms of bacterial host taxa that explain the presence of the ARGs in wastewater. The MIC tests revealed MIC(90) values of >128 µg/mL for ampicillin, ≥128 µg/mL for vancomycin, and 32 µg/mL for tetracycline. In addition, the three resistance genes, ermB, tetA, and tetM, that were present in the influent and activated sludge were still present in the effluent. These results indicate that WWTPs represent a direct route into the environment for resistance genes and do not significantly reduce their abundance. Hence, the development of treatment methods for the removal of these genes from WWTPs in the future is of utmost importance.202439816252