Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant. - Related Documents




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718401.0000Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant. Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and genes (ARB and ARGs) in wastewaters. The present work aimed to build on the current knowledge about the effects of activated sludge and UV irradiation on antibiotic resistance determinants in biologically treated wastewaters. For that, the microbial community and ARGs' composition of samples collected after preliminary (APT), secondary (AST), and tertiary (ATT) treatments in a full-scale wastewater treatment plant using a modified activated sludge (MAS) system followed by an UV stage (16 mJ/cm(2)) were investigated through culture-dependent and independent approaches (including metagenomics). A total of 24 phyla and 460 genera were identified, with predominance of Gammaproteobacteria in all samples. Pathogenic genera corresponded to 8.6% of all sequences on average, mainly Acinetobacter and Streptococcus. Significant differences (p < 0.05) in the proportion of pathogens were observed between APT and the other samples, suggesting that the secondary treatment reduced its abundance. The MAS achieved 64.0-99.7% average removal efficiency for total (THB) and resistant heterotrophic bacteria, although the proportions of ARB/THB have increased for sulfamethoxazole, cephalexin, ciprofloxacin, and tetracycline. A total of 10(7) copies/mL of intI1 gene remained in the final effluent, suggesting that the treatment did not significantly remove this gene and possibly other ARGs. In accordance, metagenomic results suggested that number of reads recruited to plasmid-associated ARGs became more abundant in the pool throughout the treatment, suggesting that it affected more the bacteria without these ARGs than those with it. In conclusion, disinfected effluents are still a potential source for ARB and ARGs, which highlights the importance to investigate ways to mitigate their release into the environment.202235060061
718310.9999Evaluation of five antibiotic resistance genes in wastewater treatment systems of swine farms by real-time PCR. Antibiotics are widely used in livestock for infection treatment and growth promotion. Wastes from animal husbandry are a potential environmental source of antibiotic-insensitive pathogens, and the removal efficiency of the resistance genotypes in current wastewater treatment plants (WWTPs) is unknown. In this study, quantitative PCR was used for evaluating antibiotic resistance genes in wastewater treatment processes. Six wastewater treatment plants in different swine farms were included in this study, and five antibiotic resistance genes (ARGs) were tested for each treatment procedure. All of the tested ARGs including tetA, tetW, sulI, sulII, and blaTEM genes were detected in six swine farms with considerable amounts. The results showed that antibiotic resistance is prevalent in livestock farming. The ARG levels were varied by wastewater treatment procedure, frequently with the highest level at anaerobic treatment tank and lowest in the activated sludge unit and the effluents. After normalizing the ARG levels to 16S rRNA gene copies, the results showed that ARGs in WWTP units fluctuated partly with the quantity of bacteria. Regardless of its importance in biodegradation, the anaerobic procedure may facilitate bacterial growth thus increasing the sustainability of the antibiotic resistance genotypes. After comparing the copy numbers in influx and efflux samples, the mean removal efficiency of ARGs ranged between 33.30 and 97.56%. The results suggested that treatments in the WWTP could partially reduce the spread of antibiotic-resistant bacteria, and additional procedures such as sedimentation may not critically affect the removal efficiency.201425064719
343220.9999Insights 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.201525957255
532330.9999Monitoring 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
718240.9999Effects 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
718550.9999Relationship between modification of activated sludge wastewater treatment and changes in antibiotic resistance of bacteria. Biological treatment processes at wastewater treatment plants (WWTPs), which are the most common methods of sewage treatment, could cause selective elimination and/or changes in the proportions of phenotypes/genotypes within bacterial populations in effluent. Therefore, WWTPs based on activated sludge used in sewage treatment constitute an important reservoir of enteric bacteria which harbour potentially transferable resistance genes. Together with treated wastewater, these microorganisms can penetrate the soil, surface water, rural groundwater supplies and drinking water. Because of this, the aim of this study was to determine the impact of various modification of sewage treatment (the conventional anaerobic/anoxic/oxic (A2/O) process, mechanical-biological (MB) system, sequencing batch reactors (SBR), mechanical-biological system with elevated removal of nutrients (MB-ERN)) on the amount of antibiotic resistant bacteria (ARB) (including E. coli) and antibiotic resistance genes (ARGs) in sewage flowing out of the 13 treatment plants using activated sludge technology. There were no significant differences in ARB and ARGs regardless of time of sampling and type of treated wastewater (p > 0.05). The highest percentage of reduction (up to 99.9%) in the amount of ARB and ARGs was observed in WWTPs with MB and MB-ERN systems. The lowest reduction was detected in WWTPs with SBR. A significant increase (p < 0.05) in the percentage of bacteria resistant to the new generation antibiotics (CTX and DOX) in total counts of microorganisms was observed in effluents (EFF) from WWTPs with A2/O system and with SBR. Among all ARGs analyzed, the highest prevalence of ARGs copies in EFF samples was observed for sul1, tet(A) and qepA, the lowest for bla(TEM) and bla(SHV). Although, the results of presented study demonstrate high efficiency of ARB and ARGs removal during the wastewater treatment processes, especially by WWTPs with MB and MB-ERN systems, EFF is still an important reservoir of ARGs which can be transferred to other microorganisms.201829791883
718660.9999Removal of selected sulfonamides and sulfonamide resistance genes from wastewater in full-scale constructed wetlands. Sulfonamides are high-consumption antibiotics that reach the aquatic environment. The threat related to their presence in wastewater and the environment is not only associated with their antibacterial properties, but also with risk of the spread of drug resistance in bacteria. Therefore, the aim of this work was to evaluate the occurrence of eight commonly used sulfonamides, sulfonamide resistance genes (sul1-3) and integrase genes intI1-3 in five full-scale constructed wetlands (CWs) differing in design (including hybrid systems) and in the source of wastewater (agricultural drainage, domestic sewage/surface runoff, and animal runs runoff in a zoo). The CWs were located in low-urbanized areas in Poland and in Czechia. No sulfonamides were detected in the CW treating agricultural tile drainage water. In the other four systems, four sulfonamide compounds were detected. Sulfamethoxazole exhibited the highest concentration in those four CWs and its highest was 12,603.23 ± 1000.66 ng/L in a CW treating a mixture of domestic sewage and surface runoff. Despite the high removal efficiencies of sulfamethoxazole in the tested CWs (86 %-99 %), it was still detected in the treated wastewater. The sul1 genes occurred in all samples of raw and treated wastewater and their abundance did not change significantly after the treatment process and it was, predominantly, at the level 10(5) gene copies numbers/mL. Noteworthy, sul2 genes were only found in the influents, and sul3 were not detected. The sulfonamides can be removed in CWs, but their elimination is not complete. However, hybrid CWs treating sewage were superior in decreasing the relative abundance of genes and the concentration of SMX. CWs may play a role in the dissemination of sulfonamide resistance genes of the sul1 type and other determinants of drug resistance, such as the intI1 gene, in the environment, however, the magnitude of this phenomenon is a matter of further research.202438081427
722670.9999Seasonal variation in antibiotic resistance genes and bacterial phenotypes in swine wastewater during three-chamber anaerobic pond treatment. Antibiotic resistance is a global public health concern. Antibiotic usage in pigs makes swine wastewater (SW) a reservoir for antibiotic resistance genes (ARGs). SW is usually stored and treated in a three-chamber anaerobic pond (3-CAP) in medium and small pig farms in northern China. However, the yet unexplored presence of ARGs in SW during 3-CAP treatment may result in ARGs spreading into the environment if farmers apply SW to farmland as a liquid organic fertilizer. This study investigated the profiles of and changes in ARGs in SW during its treatment in 3-CAP over four seasons and analyzed the correlation between ARGs and bacterial phenotypes, along with the physicochemical parameters of the water. The results revealed that ARG abundance decreased considerably after 3-CAP treatment in April (47%), October (47%), and December (62%) but increased in May (43%) and August (73%). The ARG copies in the influent and other SW samples increased significantly from 10(7) copies/mL in April to 10(9) copies/mL in October and were maintained in December. The increase in ARG abundance was not as rapid as the growth of the bacterial population, resulting in lower relative abundance in October and December. Bacterial communities possessed more sul1 and tetM genes, which were also positively correlated with mobile genetic elements. After the 3-CAP treatment, 16% of antibiotics and 60% of heavy metals were removed, and both had a weak correlation with ARGs. Predicted phenotypes showed that gram-positive (G(+)) and gram-negative (G(-)) bacteria have different capacities for carrying ARGs. G(+) bacteria carry more ARGs than G(-) bacteria. This study revealed the persistence of ARGs in SW after 3-CAP treatment over different seasons. Applying SW in the proper month will mitigate ARG dissemination to the environment.202336208778
719480.9999Response 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.202032652450
725090.9999Effect of temperature on the fate of genes encoding tetracycline resistance and the integrase of class 1 integrons within anaerobic and aerobic digesters treating municipal wastewater solids. The objective of this research was to investigate the ability of anaerobic and aerobic digesters to reduce the quantity of antibiotic resistant bacteria in wastewater solids. Lab-scale digesters were operated at different temperatures (22 °C, 37 °C, 46 °C, and 55 °C) under both anaerobic and aerobic conditions and fed wastewater solids collected from a full-scale treatment facility. Quantitative PCR was used to track five genes encoding tetracycline resistance (tet(A), tet(L), tet(O), tet(W), and tet(X)) and the gene encoding the integrase (intI1) of class 1 integrons. Statistically significant reductions in the quantities of these genes occurred in the anaerobic reactors at 37 °C, 46 °C, and 55 °C, with the removal rates and removal efficiencies increasing as a function of temperature. The aerobic digesters, in contrast, were generally incapable of significantly decreasing gene quantities, although these digesters were operated at much shorter mean hydraulic residence times. This research suggests that high temperature anaerobic digestion of wastewater solids would be a suitable technology for eliminating various antibiotic resistance genes, an emerging pollutant of concern.201021058743
7310100.9999Metagenomic 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
7094110.9999Prevalence 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
7311120.9999Sludge 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
3197130.9999Antibiotic resistance and pathogen spreading in a wastewater treatment plant designed for wastewater reuse. Climate change significantly contributes to water scarcity in various regions worldwide. While wastewater reuse is a crucial strategy for mitigating water scarcity, it also carries potential risks for human health due to the presence of pathogenic and antibiotic resistant bacteria (ARB). Antibiotic resistance represents a Public Health concern and, according to the global action plan on antimicrobial resistance, wastewater role in selecting and spreading ARB must be monitored. Our aim was to assess the occurrence of ARB, antibiotic resistance genes (ARGs), and potential pathogenic bacteria throughout a wastewater treatment plant (WWTP) designed for water reuse. Furthermore, we aimed to evaluate potential association between ARB and ARGs with antibiotics and heavy metals. The results obtained revealed the presence of ARB, ARGs and pathogenic bacteria at every stage of the WWTP. Notably, the most prevalent ARB and ARG were sulfamethoxazole-resistant bacteria (up to 7.20 log CFU mL(-1)) and sulII gene (up to 5.91 log gene copies mL(-1)), respectively. The dominant pathogenic bacteria included Arcobacter, Flavobacterium and Aeromonas. Although the abundance of these elements significantly decreased during treatment (influent vs. effluent, p < 0.05), they were still present in the effluent designated for reuse. Additionally, significant correlations were observed between heavy metal concentrations (copper, nickel and selenium) and antibiotic resistance elements (ampicillin-resistant bacteria, tetracycline-resistant bacteria, ARB total abundance and sulII) (p < 0.05). These results underscore the importance of monitoring the role of WWTP in spreading antibiotic resistance, in line with the One Health approach. Additionally, our findings suggest the need of interventions to reduce human health risks associated with the reuse of wastewater for agricultural purposes.202439357555
7227140.9999High-risk antibiotics positively correlated with antibiotic resistance genes in five typical urban wastewater. Antibiotic resistance genes (ARGs) and antibiotic amount increased within close proximity to human dominated ecosystems. However, few studies assessed the distribution of antibiotics and ARGs in multiple ecosystems especially the different urban wastewater. In this study, the spatial distribution of ARGs and antibiotics across the urban wastewater included domestic, livestock, hospital, pharmaceutical wastewater, influent of the wastewater treatment plant (WWTP) in Northeast China. The q-PCR results showed that ARGs were most abundant in community wastewater and followed by WWTP influent, livestock wastewater, pharmaceutical wastewater and hospital wastewater. The ARG composition differed among the five ecotypes with qnrS was the dominant ARG subtypes in WWTP influent and community wastewater, while sul2 dominant in livestock, hospital, pharmaceutical wastewater. The concentration of antibiotics was closely related to the antibiotic usage and consumption data. In addition to the high concentration of azithromycin at all sampling points, more than half of the antibiotics in livestock wastewater were veterinary antibiotics. However, antibiotics that closely related to humankind such as roxithromycin and sulfamethoxazole accounted for a higher proportion in hospital wastewater (13.6%) and domestic sewage (33.6%), respectively. The ambiguous correlation between ARGs and their corresponding antibiotics was detected. However, antibiotics that exhibited high ecotoxic effects were closely and positively correlated with ARGs and the class 1 integrons (intI1), which indicated that high ecotoxic compounds might affect antimicrobial resistance of bacteria by mediating horizontal gene transfer of ARGs. The coupling mechanism between the ecological risk of antibiotics and bacterial resistance needed to be further studied, and thereby provided a new insight to study the impact of environmental pollutants on ARGs in various ecotypes.202337267763
7093150.9999Class 1 integrase, sulfonamide and tetracycline resistance genes in wastewater treatment plant and surface water. Wastewater treatment plants are considered hot spots for multiplication and dissemination of antibiotic-resistant bacteria and resistance genes. In this study, we determined the presence of class 1 integron integrase and genes conferring resistance to tetracyclines and sulfonamides in the genomes of culturable bacteria isolated from a wastewater treatment plant and the river that receives the treated wastewater. Moreover, using PCR-based metagenomic approach, we quantified intI1, tet and sul genes. Wastewater treatment caused the decrease in the total number of culturable heterotrophs and bacteria resistant to tetracycline and sulfonamides, along with the decrease in the number of intI1, sul and tet gene copies per ml, with significant reduction of tet(B). On the other hand, the treatment process increased both the frequency of tetracycline- and sulfonamide-resistant bacteria and intI1-positive strains, and the relative abundance of all quantified antibiotic resistance genes (ARGs) and intI1 gene; in the case of tet(A) and sul2 significantly. The discharge of treated wastewater increased the number of intI1, tet and sul genes in the receiving river water both in terms of copy number per ml and relative abundance. Hence, despite the reduction of the number of ARGs and ARBs, wastewater treatment selects for bacteria with ARGs in effluent.201626519797
5325160.9999Genes 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
7123170.9998Presence and fate of antibiotic residues, antibiotic resistance genes and zoonotic bacteria during biological swine manure treatment. The presence and dissemination of antibiotic residues, antibiotic resistance genes and zoonotic bacteria in the environment is of growing concern worldwide. Manure management practices, such as biological removal of nitrogen from swine manure, may help to decrease levels of antibiotic residues, antibiotic resistance genes and zoonotic bacteria present in manure before fertilization, thereby reducing environmental contamination. Therefore, the aim of this study was to monitor the presence and fate of seven antibiotic residues (colistin, sulfadiazine, trimethoprim, doxycycline, oxytetracycline, ceftiofur and tylosin A), nine antibiotic resistance genes (tet(B), tet(L), tet(M), tet(O), tet(Q), tet(W), erm(B), erm(F) and sul2) and two zoonotic bacteria (Salmonella Typhimurium and Campylobacter coli) during biological nitrogen removal from swine manure over time. Samples from the raw manure, the solid fraction, the liquid fraction and the storage lagoon were analyzed on two farms at six time points with an interval of two weeks. Only the antibiotics which were used during the three months preceding the first sampling could be detected before and after biological nitrogen removal from swine manure. Of all the antibiotics studied, doxycycline was recovered in all of the samples and sulfadiazine was recovered in most samples on both farms. For both antibiotics, there appears to be a reduction of the amount of residues present in the storage lagoon compared to the liquid fraction, however, this reduction was not statistically significant. A significant reduction of the relative abundances of most of the antibiotic resistance genes studied was observed when comparing the liquid fraction and the storage lagoon. For tet(L), no differences were observed between the fractions sampled and for sul2 and erm(F), a significant increase in relative abundances was observed on the second farm sampled. For the zoonotic bacteria, a reduction of at least 1 log was observed after biological nitrogen removal from swine manure. The results indicate that the concentration of certain antibiotic residues and several antibiotic resistance genes and the amount of zoonotic bacteria present in the manure may be reduced in the end product of the biological nitrogen removal from swine manure.201930878661
7195180.9998Insight 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
3678190.9998Abundance and dynamics of antibiotic resistance genes and integrons in lake sediment microcosms. Antibiotic resistance in bacteria causing disease is an ever growing threat to the world. Recently, environmental bacteria have become established as important both as sources of antibiotic resistance genes and in disseminating resistance genes. Low levels of antibiotics and other pharmaceuticals are regularly released into water environments via wastewater, and the concern is that such environmental contamination may serve to create hotspots for antibiotic resistance gene selection and dissemination. In this study, microcosms were created from water and sediments gathered from a lake in Sweden only lightly affected by human activities. The microcosms were exposed to a mixture of antibiotics of varying environmentally relevant concentrations (i.e., concentrations commonly encountered in wastewaters) in order to investigate the effect of low levels of antibiotics on antibiotic resistance gene abundances and dynamics in a previously uncontaminated environment. Antibiotic concentrations were measured using liquid chromatography-tandem mass spectrometry. Abundances of seven antibiotic resistance genes and the class 1 integron integrase gene, intI1, were quantified using real-time PCR. Resistance genes sulI and ermB were quantified in the microcosm sediments with mean abundances 5 and 15 gene copies/10(6) 16S rRNA gene copies, respectively. Class 1 integrons were determined in the sediments with a mean concentration of 3.8 × 10(4) copies/106 16S rRNA gene copies. The antibiotic treatment had no observable effect on antibiotic resistance gene or integron abundances.201425247418