Search

Peracetic acid (PAA) is an emerging disinfectant with a low disinfection by-product formation potential, but how PAA destroys gene function after killing bacteria remains to be studied. Bacterial plasmid DNA is a mobile genetic element that often harbors undesirable genes encoding antibiotic resistance and virulence factors. Even though PAA efficiently kills bacteria, bacterial plasmids and other mobile genetic elements might still be intact and functional after PAA disinfection, posing potential public health and environmental risks. This study evaluated the impact of PAA disinfection on the functionality of plasmid DNA in vivo and compared the results with those from chlorination. We delivered a plasmid DNA harboring two antibiotic resistance genes to Escherichia coli TOP10 to form an antibiotic-resistant bacterium (ARB). The planktonic ARB was treated with PAA and chlorine to find the minimum doses inhibiting the regrowth of the strain. PAA and chlorine stopped the regrowth at 8 ± 1 mg PAA·L−1 and 20 ± 9 mg Cl 2 ·L−1, respectively. The functionality of the plasmid DNA after PAA and chlorine disinfection was then determined at higher doses in vivo. Neither PAA nor chlorine completely destroyed the plasmid DNA. However, chlorine was more efficient than PAA in eliminating the plasmid DNA. PAA at 25 mg PAA·L−1 reduced the transforming activity of the plasmid DNA by less than 0.3 log 10 units, whereas chlorine at 25 mg Cl 2 ·L−1 reduced the transforming activity by approximately 1.7 log 10 units. Chlorine had a more pronounced impact on the functionality of the plasmid DNA because it oxidizes or destroys bacterial components including plasmid DNA faster than PAA. In addition, environmental scanning electron microscopy shows that chlorination desiccated the cells resulting in the flat cellular structure and possibly more complete loss of plasmid DNA, whereas PAA disinfection had a less impact on cell structure and morphology. This study demonstrates that more plasmid DNA remains functional in water after PAA disinfection than after chlorination. These functional genetic elements could be acquired by other microorganisms via horizontal gene transfer to pose potential public health and environmental risks. Unlabelled Image • Functionality of plasmid DNA was investigated in vivo after peracetic acid (PAA) disinfection. • PAA was more efficient than chlorine in preventing bacterial regrowth. • Neither PAA nor chlorine completely destroyed plasmid while preventing bacterial regrowth. • More plasmid remained functional after PAA disinfection than after chlorination. • Plasmid after PAA and chlorine disinfection can be acquired by microbes to pose environmental risks. [ABSTRACT FROM AUTHOR]

The peri-urban rivers are one of the critical interfaces between urban-rural symbiotic ecosystems and appear to be a reservoir of antibiotic resistance genes (ARGs) in the environment. To prevent the transmission risks of ARGs between peri-urban river and human, it is essential to explore the prevalence and source of ARGs in the environment for designing potential mitigation strategies. In this study, we focused on the characterization and source-tracking of ARGs in the sediments of a typical peri-urban river in Beijing, Chaobai River. Twenty-seven ARGs frequently reported in the environment, and two integrons (intI1 and intI2) were detected using high-throughput quantitative PCR. The profile of bacterial community was determined by performing 16S rRNA gene sequencing. Meanwhile, crAssphage , a novel recently-discovered DNA bacteriophage, was employed for tracking the contribution of human fecal pollution to the prevalence of ARGs. Results showed that the targeted ARGs were detected widely in the sediments of Chaobai River. Relatively, the abundances of ARGs in downstream were higher than those in the upstream, likely suggesting a gradient impact of anthropogenic activities along the river. Remarkably, the int1 gene was correlated significantly with most of the ARGs and might be the key factor influencing the shaping of ARGs in the river sediments. However, no significant correlations were observed between the ARGs and selective pressure factors, including antibiotics and metals. Of the identified 1039 genera, Escherichia - Shigella , Bacteroides , Arcobacter , Dechloromonas and Pseudomonas were the top most abundant organisms. Microbial source tracking based on the crAssphage annotation suggested that human sewage might be one of the potential sources of resistance bacteria in the river sediments. The study can advance our knowledge about ARGs in the peri-urban river and provides a management reference for ARG pollution control. Unlabelled Image • A variety of ARGs were widely detected in the sediments of a peri-urban river. • Class 1 integron potentially affected the shaping of ARGs in the river. • A gradient in anthropogenic impacts on ARGs was observed along the river. • CrAssphage-based metagenomics approach was used for microbial source tracking. • Human fecal pollution was identified as potential source of ARGs in the river. [ABSTRACT FROM AUTHOR]

Abstract The use of antibiotics in aquaculture causes selection pressure for antibiotic-resistant bacteria (ARB). Antibiotic resistance genes (ARGs) may persist in ARB and the environment for long time even after stopping drug administration. Here we show monthly differences in the occurrences of genes conferring resistance to sulfonamides (i.e. sul1 , sul2 , sul3), and tetracyclines (tet (M)) in Japanese aquaculture seawater accompanied by records of drug administration. sul2 was found to persist throughout the year, whereas the occurrences of sul1 , sul3 , and tet (M) changed month-to-month. sul3 and tet (M) were detected in natural bacterial assemblages in May and July, but not in colony-forming bacteria, thus suggesting that the sul3 was harbored by the non-culturable fraction of the bacterial community. Comparison of results from Taiwanese, Japanese, and Finnish aquaculture waters reveals that the profile of sul genes and tet (M) in Taiwan resembles that in Japan, but is distinct from that in Finland. To our knowledge, this work represents the first report to use the same method to compare the dynamics of sul genes and tet (M) in aquaculture seawater in different countries. Graphical abstract Unlabelled Image Highlights • sul1-3 and tet(M) were quantitated in seawater and cultured bacteria in Japanese mariculture. • sul2 was consistently abundant in the sea, whereas others varied depending on the month. • sul3 was present in non-culturable bacteria in seawater, but not in cultured bacteria. • Resistance gene profiles among Japan, Taiwan and Finland were different. [ABSTRACT FROM AUTHOR]

Abstract The pollution of various environments with antibiotic resistance genes (ARGs) is an urgent problem that needs to be addressed, especially in heavy metal-polluted environments. This study investigated the responses of ARGs and mobile genetic elements (MGEs) to the addition of graphene oxide (GO) to swine manure containing a high concentration copper during anaerobic digestion. The total copy numbers of ARGs and MGEs were significantly enhanced by the pressure due to Cu. GO significantly decreased the ARG and MGE copy numbers, where the low GO concentration performed better than the high GO concentration. Network analysis showed that most of the ARGs and MGEs co-occurred and they shared the same major potential host bacteria. The contributions of different factors to ARG abundances were assessed by redundancy analysis and MGEs had the most important effect on the fate of ARGs. Thus, GO may reduce the abundance of ARGs mainly by removing MGEs. Graphical abstract Unlabelled Image Highlights • GO was effective in reducing the copy numbers of ARGs and MGEs. • The abundance of ARGs was reduced mainly by GO hindering the horizontal transfer. • The contribution of environmental to ARGs was through bacterial community. • Potential host bacteria for MRGs have significant correlations with most ARGs. [ABSTRACT FROM AUTHOR]

Abstract Sawdust, rice husk, and mushroom residues are commonly used as bulking agents during manure composting; this work evaluated their potentiality for enhancing the removal of antibiotics and antibiotic resistance genes (ARGs) under a temperature-consistent condition. Results indicated that the addition of all the compost-bulking agents increased antibiotic removal in swine manure with increasing rates of 14.9%–33.4%; however they showed less effect on the reduction of residual antibiotics in chicken manure where fluoroquinolone (FQs) antibiotics are the dominant antibiotics, partly owing to the weak promoting effects of bulking agents on FQs degradation. The addition of bulking agents somehow hindered the reduction of ARGs within swine manure, whereas there were obvious reductions in the total relative abundance of ARGs in chicken manure with bulking agents added. Among the three bulking agents, sawdust was the most efficient enhancer for antibiotic removal in both manures, and rice husk exhibited the best performance on ARGs reduction in chicken manure. The relationship between antibiotics, ARGs and bacteria communities was subsequently delineated. Proteobacteria was proposed to play key roles on the effect of bulking agent addition on antibiotics and ARGs in swine manure. Particularly, the increased Xanthomonadaceae contributed much to the promoted antibiotic degradation as well as the high level of ARGs in swine manure with sawdust added. By contrast, the changes in dominant bacterial families by the addition of bulking agents into chicken manure were not strong enough to effectively enhance antibiotic removal, but largely influenced the ARGs abundance. The large reductions of Paenibacillaceae and Staphylococcaceae by rice husk addition were closely related to the reduced ARGs in chicken manure with rice husk added. Graphical abstract Unlabelled Image Highlights • Bulking agents enhance antibiotics and ARGs removal without affecting temperature. • The effects of bulking agents on antibiotics and ARGs fates vary with manure types. • Sawdust is the most efficient enhancer for antibiotic removal in manures. • Rice husk added into chicken manure effectively reduces ARGs. • Antibiotics degrading and ARGs carrying responders to bulking agents were identified. [ABSTRACT FROM AUTHOR]

The riverine system is usually considered as a natural reservoir of antibiotic resistance genes (ARGs) and more susceptible to anthropogenic activities. In this study, the occurrence and distribution of 14 antibiotics belonging to 7 categories together with 23 corresponding ARGs in Ba River of Xi'an China were investigated in March and July 2017. Sulfonamides, quinolones, macrolides and tetracyclines were detected in high frequencies ranged from 85.7% to 100%. Tetracyclines were detected with high concentrations in water samples (up to 8.54 × 10 2  ng L −1 ) and sediment samples (up to 2.08 × 10 3  μg kg −1 ), respectively. The total concentrations of antibiotics were much higher in July in comparison with March. The sul 1, tet A, tet C, tet Z, gyr A, erm F, cml A and bla TEM were the predominant ARGs in terms of absolute abundance. For both water and sediment samples in March compared with July, the relative abundance of ARGs had no significant difference except for sul 3. The tetracyclines had positive correlation with tet genes, whereas the remaining antibiotics had no significant correlations with their corresponding ARGs, suggesting that environmental factors and cross-selection may significantly influenced the distribution of ARGs. Redundancy analysis was performed to further predict the influences of environmental factors on antibiotics and ARG abundance. The findings suggest that anthropogenic activities contribute significantly to the persistence of antibiotics pollution. [ABSTRACT FROM AUTHOR]

Antibiotic resistance genes (ARGs) in environment have become a growing public concern, due to their potential to be obtained by pathogens and their duplication along cell division. Horizontal gene transfer (HGT) was reported to be responsible for ARGs dissemination in microbes, but the HGT feature in environmental biofilm was still unclear due to insufficient assay tools. To address this challenge, we applied a novel microfluidic system to cultivate thin biofilm by continuous supply of nutrients and close contact between cells. Resembling the living state of biofilm in open environment, this chip visualized the transfer of ARG-encoded plasmids RP4 and pKJK5 to the receptors, e.g., activated sludge bacteria. The average plasmid transfer frequency per receptor (T/R) from RP4-hosted Pseudomonas putida KT2440 to activated sludge bacteria was quantified to be 2.5 × 10 −3 via flow cytometry, and T/R for pKJK5-hosted Escherichia coli MG1655 was 8.9 × 10 −3 , while the corresponding average frequencies per donor (T/D) were diverse for the two host strains as 4.3 × 10 −3 and 1.4 × 10 −1 respectively. The difference between T/R and T/D was explained by the plasmid transfer kinetics, implying specific purposes of the two calculations. Finally, we collected the transconjugants by fluorescent activated cell sorting and further sequenced their 16S rDNA. Bacteria from phyla Proteobacteria and Firmicutes were found more susceptible to be transconjugants than those from Bacteroidetes . Our work demonstrated that microfluidic system was advantageous in biofilm HGT study, which can provide more insights into environmental ARG control. [ABSTRACT FROM AUTHOR]

The application of dairy wastewater to agricultural soils is a widely used practice to irrigate crops and recycle nutrients. In this study, small-scale field plots were irrigated monthly (6 times) with dairy wastewater (100%), wastewater diluted to 50% with irrigation (canal) water, and diluted wastewater spiked with copper sulfate (50 mg Cu L −1 ), while control plots were irrigated with canal water. In addition, half of all plots were either planted with wheat or were left as bare soil. Biweekly soil samples were collected during this period and processed to determine the occurrence and abundance of antibiotic resistance genes [ bla CTX-M-1 , erm (B), sul1 , tet (B), tet (M), and tet (X)] and a class 1 integron-integrase gene ( intI1 ) via quantitative real-time PCR (qPCR). Only sul1 and tet (X) were detected in soil (3 out of 32 samples) before the wastewater treatments were applied. However, the occurrence and relative abundance (normalized to 16S rRNA gene copies) of most genes [ erm (B), intI1 , sul1 , and tet (M)] increased dramatically after wastewater irrigation and levels were maintained during the entire study period. bla CTX-M-1 was the only gene not detected in wastewater-treated soils, which is likely related to its absence in the dairy wastewater. Relative gene levels in soil were found to be statistically similar among the treatments in most cases, regardless of the wastewater percentage applied and presence or absence of plants. The key result from this study is that dairy wastewater irrigation significantly enlarges the reservoir of ARGs and intI1 in soils, while detection of these genes rarely occurred in soil irrigated only with canal water. In addition, elevated levels of Cu in the wastewater and treated soil did not produce a concomitant increase of the ARG levels. [ABSTRACT FROM AUTHOR]

Antibiotic resistance genes (ARGs) are found in marine as well as terrestrial bacteria. Bivalves are known to accumulate chemical pollutants and pathogenic microbes, however, the fate of ARGs in bivalves after the intake of ARG-possessing bacteria is not known. Here we show that the copy number of oxytetracycline resistance gene tet (M) increased rapidly in the clam digestive tract by filtering water, then remained constant over 96 h in a tank experiment even with the addition of tet (M)-possessing bacteria every 24 h. >99.9% of the added tet (M) was decomposed, reaching a balanced state. Environmental sampling of mussel digestive tract and seawater supported the hypothesis that tet (M) was decomposed in bivalves as tet (M) was present in seawater from April to October at a concentration of 10 −5 to 10 −6 copies/16S, whereas tet (M) in mussels was mostly below the detection limit. Two (April) and three (July and October) individual mussels were positive for tet (M) with a concentration equivalent to that of seawater. We therefore conclude that bivalves do not accumulate tet (M) from seawater. [ABSTRACT FROM AUTHOR]

Spread of antibiotic resistance genes (ARGs) originating from sewage sludge is highlighted as an eminent health threat. This study established a thermophilic anaerobic digester using one-step startup strategy to quickly remove tetracycline and sulfonamides resistance genes from sewage sludge. At least 20 days were saved in the startup period from mesophilic to thermophilic condition. Based on the results of 16S rDNA amplicons sequencing and predicted metagenomic method, the successful startup largely relied on the fast colonization of core thermophilic microbial population (e.g. Firmicutes , Proteobacteria , Actinobacteria ). Microbial metabolic gene pathways for substrate degradation and methane production was also increased by one-step mode. In addition, real-time quantitative PCR approach revealed that most targeted tetracycline and sulfonamides resistance genes ARGs ( sul I, tet A, tet O, tet X) were substantially removed during thermophilic digestion (removal efficiency > 80%). Network analysis showed that the elimination of ARGs was attributed to the decline of their horizontal ( int I1 item) and vertical (potential hosts) transfer-related elements under high-temperature. This research demonstrated that rapid startup thermophilic anaerobic digestion of wastewater solids would be a suitable technology for reducing quantities of various ARGs. [ABSTRACT FROM AUTHOR]

Pharmaceutical wastewater treatment plants (PWWTPs), which receive wastewater containing extremely high levels of antibiotics, are regarded as potential hot spots for antibiotic-resistance development in the environment. Six sampling campaigns in six PWWTPs in Southeastern China were carried out to assess the prevalence and fate of antibiotic resistance genes (ARGs). Different genes were monitored in different PWWTPs (PWWTP A: lincosamides; PWWTP B: aminoglycosides and macrolides; PWWTP C: quinolones; PWWTP D: macrolides and quinolones; PWWTP E: cephalosporins; and PWWTP F: quinolones and macrolides) using real-time quantitative polymerase chain reactions (PCRs), according to the antibiotic type produced. The levels of typical ARG subtypes in the final effluents ranged from (1.03 ± 0.91) × 10 1 to (6.78 ± 0.21) × 10 7 copies/mL. The absolute abundance of ARGs in effluents accounted for 0%–577% of influents to the six PWWTPs with a median value of 6%. Most of the ARGs are transported to the dewatered sludge, with concentrations from (1.38 ± 0.21) × 10 5 to (6.84 ± 0.43) × 10 10 copies/g dry weight (dw). In different treatment units (before/after biological units), a clear trend of proliferation or attenuation was not observed for the ARGs, aside from a strong attenuation in moving bed bio-film reactor (MBBR) in PWWTP C. Through correlation analyses, this study demonstrated that the bacterial abundance and antibiotic concentrations within the PWWTPs influenced the fate of the associated ARGs, and this was possibly related primarily to the intrinsic resistance mechanisms of corresponding ARGs. Macrolide ARGs, which tend to locate in plasmids and transposons, positively correlate weakly with total macrolide antibiotic concentrations but positively correlate strongly with 16S rRNA concentrations. Furthermore, ARG concentrations in the wastewater from fermentation were significantly higher than in the wastewater from chemical synthesis and preparation. This is the first comprehensive study on the behavior of antibiotic resistance genes under extremely high-level antibiotic selection pressures in pharmaceutical wastewater treatment plants (PWWTPs) in Southeastern China. [ABSTRACT FROM AUTHOR]

Animal manure is a main reservoir of antibiotic residues and antibiotic resistance. Here, the effect of temperature on sulfonamide antibiotics (SAs), sulfonamide-resistant (SR) genes/bacteria was investigated by aerobically incubating swine and chicken manures at different temperatures. In swine manure, the SAs concentration declined with increasing temperature, with a minimum at 60 °C. In chicken manure, the greatest degradation of SAs was noted at 30 °C. The reduction of relative abundance of antibiotic resistance genes (ARGs) and sul -positive hosts in swine manure was more pronounced during thermophilic than mesospheric incubation; neither temperature conditions effectively reduced these parameters in chicken manure. The relationship between the residual levels/distribution profiles of SAs, ARGs ( sul1 , sul2 and intI1 ), cultivable SR bacteria and sul -positive hosts was further established. The antibiotic residual profile, rather than antibiotic concentration, acted as an important factor in the prevalence of ARGs and sul -positive hosts in manure. Corynebacterium and Leucobacter from the phylum Actinobacteria tend to be main carriers of sul1 and intI1 ; the relative abundance of sul2 was significantly correlated with the relative abundance of cultivable SR bacteria. Overall, differences in resistant bacterial communities also constitute a dominant factor affecting ARG variation. This study contributes to management options for reducing the pollution of antibiotics and antibiotic resistance within manure. [ABSTRACT FROM AUTHOR]

Chinese wet markets with live poultry trade have been considered as major sources of pathogen dissemination, and sites for horizontal transfer of bacterial and viral pathogens. In this study, the pathogenic bacteria and antibiotic resistant genes (ARGs) in air samples collected at a typical Chinese wet market had been analysis and quantified. Corynebacterium minutissimum and other pathogenic bacteria accounted for 0.81–8.02% of the whole microbial community in different air samples. The four ARGs quantified in this study showed a comparable relative concentration (copies/ng_DNA) with municipal wastewater. Poultry manures were demonstrated to be important microbial contamination source in wet market, which was supported by both microbial composition based source tracking and the quantification of airborne microbial density. A series of Firmicutes and Bacteroidetes indicators of poultry area contamination were successfully screened, which will be useful for the more convenient monitoring of airborne poultry area contamination. Our results indicate bioaerosols acted as important route for the transmissions of pathogens and ARGs. Continued surveillance of airborne microbial contamination is required in poultry trade wet market. Practical implications Urban live poultry markets are important sources of pathogen dissemination, and sites for horizontal transfer of viral and bacterial pathogens. In the present field-study, pathogenic bacteria and antibiotic resistance genes were focused to provide quantitative information on the levels of microbial contaminations at the indoor air of wet markets. Results demonstrated that poultry manures were important microbial contamination source in wet market, and in the meanwhile bioaerosols were identified as important route for the transmissions of microbial contaminants. A series of Firmicutes and Bacteroidetes indicators of poultry area contamination were successfully screened, which will be useful for the more convenient monitoring of airborne poultry area contamination. [ABSTRACT FROM AUTHOR]

With the exacerbating problem of antibiotic resistance, antibiotic resistance genes (ARGs) as emerging contaminants are found at elevated levels in inland aquatic environments, especially in regions of intensive agricultural and urban activity. However, little quantitative data exist on the migration and attenuation of ARGs in estuary ecosystem, which is central to predicting their fate after release into marine environment. Moreover, the relevance of multiple chemical contaminants and water quality constituents should be understood to amplify and attenuate antibiotic resistance levels. To determine the prevalence and examine the fate of sulfonamide ARGs ( sul -ARGs) in two estuaries under different effects of anthropogenic activities, we analyzed the sul -ARGs ( sul1 , sul2 , and sul3 ), class 1 integrons ( int1 ), and bacterial biomass in surface water samples from Daliaohe and Liaohe river estuaries. We also evaluated five types of antibiotics, heavy metals, and various bulk water quality constituents. Results showed that sul -ARGs were widespread in Daliaohe and Liaohe river estuaries, but the distribution did not correlate with the concentration of sulfonamides. Significant reduction in the abundance of sul -ARGs was also observed with increased salinity. Nevertheless, the trend in the change of concentrations of sul -ARGs was different in the two estuaries. Statistical analysis of the results indicated that several metals were significantly and positively correlated with sul -ARGs. Pearson's correlation coefficients were higher than those determined between antibiotic residues and sul -ARGs. Furthermore, the relative abundance of sul -ARGs was significantly and positively correlated with the relative abundance of int1 which suggested that the propagation of sul -ARGs was facilitated by class 1 integrons in estuaries. [ABSTRACT FROM AUTHOR]

This study investigated the characteristics of 10 subtypes of antibiotic resistance genes (ARGs) for sulfonamide, tetracycline, β-lactam and macrolide resistance and the class 1 integrase gene ( intI1 ). In total, these genes were monitored in 24 samples across each stage of five full-scale pharmaceutical wastewater treatment plants (PWWTPs) using qualitative and real-time quantitative polymerase chain reactions (PCRs). The levels of typical ARG subtypes in the final effluents ranged from (2.08 ± 0.16) × 10 3 to (3.68 ± 0.27) × 10 6 copies/mL. The absolute abundance of ARGs in effluents accounted for only 0.6%–59.8% of influents of the five PWWTPs, while the majority of the ARGs were transported to the dewatered sludge with concentrations from (9.38 ± 0.73) × 10 7 to (4.30 ± 0.81) × 10 10 copies/g dry weight (dw). The total loads of ARGs discharged through dewatered sludge was 7–308 folds higher than that in the raw influents and 16–638 folds higher than that in the final effluents. The proliferation of ARGs mainly occurs in the biological treatment processes, such as conventional activated sludge, cyclic activated sludge system (CASS) and membrane bio-reactor (MBR), implying that significant replication of certain subtypes of ARGs may be attributable to microbial growth. High concentrations of antibiotic residues (ranging from 0.14 to 92.2 mg/L) were detected in the influents of selected wastewater treatment systems and they still remain high residues in the effluents. Partial correlation analysis showed significant correlations between the antibiotic concentrations and the associated relative abundance of ARG subtypes in the effluent. Although correlation does not prove causation, this study demonstrates that in addition to bacterial growth, the high antibiotic residues within the pharmaceutical WWTPs may influence the proliferation and fate of the associated ARG subtypes. [ABSTRACT FROM AUTHOR]

Abstract: The presence of antibiotics in the natural environment has been a growing issue. This presence could also account for the influence that affects microorganisms in such a way that they develop resistance against these antibiotics. The aim of this study was to evaluate whether the antibiotic resistant gene (ARG) plasmid transfer can be facilitated by the impact of 1) environmentally representative micro-contaminant concentrations in ppb (part per billion) levels and 2) donor-recipient microbial complexity (pure vs. mixed). For this purpose, the multidrug resistant plasmid, pB10, and Escherichia coli DH5α were used as a model plasmid and a model donor, respectively. Based on conjugation experiments with pure (Pseudomonas aeruginosa PAKexoT) and mixed (activated sludge) cultures as recipients, increased relative plasmid transfer frequencies were observed at ppb (μg/L) levels of tetracycline and sulfamethoxazole micro-contaminant exposure. When sludge, a more complex community, was used as a recipient, the increases of the plasmid transfer rate were always statistically significant but not always in P. aeruginosa. The low concentration (10ppb) of tetracycline exposure led to the pB10 transfer to enteric bacteria, which are clinically important pathogens. [Copyright &y& Elsevier]

Abstract: Livestock manure treatment and storage structures are potential environmental sources of antimicrobials and antimicrobial resistance genes (ARGs). In this study, the occurrence of antimicrobials and ARGs was investigated in the water and the sludge compartments of beef cattle storage ponds and swine lagoons. Analysis was focused on two families of antimicrobials (sulfonamide and tetracycline) and the corresponding ARGs (sul1, sul2, tetO, tetQ and tetX). Results showed that the pseudo-partitioning coefficients of tetracyclines were higher than those of sulfonamides, suggesting different distributions of these two classes of antimicrobials between water and sludge. The ARGs tested were detected in nearly all ponds and lagoons, with the highest relative abundance in sul2 at 6.3×10−1 copies per 16S rRNA gene. A positive correlation was observed between total sul genes and total sulfonamides in water while the correlation was negative in sludge. No significant correlation was found between total tet genes and total tetracyclines in either water or sludge, but significant correlations were observed for certain individual tet genes. Ammonia concentrations strongly correlated with all ARGs except tetX. This study provided quantitative information on the occurrence of antimicrobials and ARGs in the liquid and solid compartments of typical manure treatment and storage structures. [Copyright &y& Elsevier]

Abstract: Antibiotics and corresponding resistance genes and resistant bacteria have been considered as emerging pollutants worldwide. Wastewater treatment plants (WWTPs) are potential reservoirs contributing to the evolution and spread of antibiotic resistance. In this study, total concentrations of tetracycline and sulfonamide antibiotics in final effluent were detected at 652.6 and 261.1ng/L, respectively, and in treated sludge, concentrations were at 1150.0 and 76.0μg/kg dry weight (dw), respectively. The quantities of antibiotic resistance genes and antibiotic resistant bacteria in final effluent were quantified in the range of 9.12×105–1.05×106 gene abundances /100mL (genomic copies/100mL) and 1.05×101–3.09×103 CFU/mL, respectively. In treated sludge, they were quantified at concentrations of 1.00×108–1.78×109 gene abandances/100mL and 7.08×106–1.91×108 CFU/100mL, respectively. Significant reductions (2–3 logs, p <0.05) of antibiotic resistance genes and antibiotic resistant bacteria were observed between raw influent and final effluent. The gene abundances of tetO and tetW normalized to that of 16S rRNA genes indicated an apparent decrease as compared to sulI genes, which remained stable along each treatment stage. Significant correlations (R2 =0.75–0.83, p <0.05) between numbers of resistant bacteria and antibiotic concentrations were observed in raw influent and final effluent. No significance (R2 =0.15, p >0.05) was found between tet genes (tetO and tetW) with concentration of tetracyclines identified in wastewater, while a significant correlation (R2 =0.97, p <0.05) was observed for sulI gene and total concentration of sulfonamides. Correlations of the quantities of antibiotic resistance genes and antibiotic resistant bacteria with corresponding concentrations of antibiotics in sludge samples were found to be considerably weak (R2 =0.003–0.07). [Copyright &y& Elsevier]