Dynamics of class 1 integrons in aerobic biofilm reactors spiked with antibiotics. - Related Documents




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343801.0000Dynamics of class 1 integrons in aerobic biofilm reactors spiked with antibiotics. Class 1 integrons are strongly associated with the dissemination of antibiotic resistance in bacteria. However, little is known about whether the presence of antibiotics affects the abundance of integrons and antibiotic resistance genes during biological wastewater treatment. To explore the roles of class 1 integrons in spreading antibiotic resistance genes in environmental compartments, the dynamics of integrons were followed in biofilm reactors treating synthetic wastewater respectively spiked with streptomycin (STM) and oxytetracycline (OTC). The relative abundance of the integron-integrase gene (intI1) increased 12 or 29-fold respectively when treated with STM or OTC, under incrementally increasing dosage regimes from 0 to 50 mg L(-1). Significant increases in intI1 abundance initially occurred at an antibiotic dose of 0.1 mg L(-1). At the beginning of the experiment, 51% to 64% of integrons carried no gene cassettes. In STM and OTC spiked systems, there was a significant increase in the proportion of integrons that contained resistance gene cassettes, particularly at intermediate and higher antibiotic concentrations. Gene cassettes encoding resistance to aminoglycosides, trimethoprim, beta-lactam, erythromycin, and quaternary ammonium compounds were all detected in the treated systems. Three tetracycline resistance genes (tetA, tetC, tetG) were significantly correlated with the abundance of intI1 (p < 0.01), despite no tet resistance being present as a gene cassette. Genome sequencing of isolates showed synteny between the tet resistance genes and intI1, mediated through linkage to transposable elements including Tn3, IS26 and ISCR3. Class 1 integrons appeared to be under positive selection in the presence of antibiotics, and might have actively acquired new gene cassettes during the experiment.202032474215
532510.9998Genes 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
709420.9998Prevalence 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
352130.9998Indirect evidence of transposon-mediated selection of antibiotic resistance genes in aquatic systems at low-level oxytetracycline exposures. Subinhibitory levels of antibiotics can promote the development of antibiotic resistance in bacteria. However, it is unclear whether antibiotic concentrations released into aquatic systems exert adequate pressure to select populations with resistance traits. To examine this issue, 15 mesocosms containing pristine surface water were treated with oxytetracycline (OTC) for 56 days at five levels (0, 5, 20, 50, and 250 microg L(-1)), and six tetracycline-resistance genes (tet(B), tet(L), tet(M), ted(O), tet(Q), and tet(W)), the sum of those genes (tet(R)), "total" 16S-rRNA genes, and transposons (Tn916 and Tn 1545) were monitored using real-time PCR. Absolute water-column resistance-gene abundances did not change at any OTC exposure. However, an increase was observed in the ratio of tet(R) to 16S-rRNA genes in the 250 microg L(-1) OTC units, and an increase in the selection rate of Tc(r) genes (relative to 16S-rRNA genes) was seen when OTC levels were at 20 microg L(-1). Furthermore, tet(M) and Tn916/1545 gene abundances correlated among all treatments (r2 = 0.701, p = 0.05), and there were similar selection patterns of tetR and Tn916/1545 genes relative to the OTC level, suggesting a possible mechanism for retention of specific resistance genes within the systems.200818754392
529140.9998Low-Concentration Ciprofloxacin Selects Plasmid-Mediated Quinolone Resistance Encoding Genes and Affects Bacterial Taxa in Soil Containing Manure. The spread of antimicrobial resistance in environment is promoted at least in part by the inappropriate use of antibiotics in animals and humans. The present study was designed to investigate the impact of different concentrations of ciprofloxacin in soil containing manure on the development of plasmid-mediated quinolone resistance (PMQR) - encoding genes and the abundance of soil bacterial communities. For these studies, high-throughput next-generation sequencing of 16S rRNA, real-time polymerase chain reaction and standard microbiologic culture methods were utilized. We demonstrated that the dissipate rate of relative abundances of some of PMQR-encoding genes, such as qnrS, oqxA and aac(6('))-Ib-cr, were significantly lower with ciprofloxacin 0.04 and 0.4 mg/kg exposure as compared to no-ciprofloxacin control and ciprofloxacin 4 mg/kg exposure during 2 month. Also, the number of ciprofloxacin resistant bacteria was significantly greater in ciprofloxacin 0.04 and 0.4 mg/kg exposure as compared with no-ciprofloxacin control and the ciprofloxacin 4 mg/kg exposure. In addition, lower ciprofloxacin concentration provided a selective advantage for the populations of Xanthomonadales and Bacillales in orders while Agrobacterium, Bacillus, Enterococcus, and Burkholderia in genera. These findings suggest that lower concentration of ciprofloxacin resulted in a slower rate of PMQR-encoding genes dissipation and selected development of ciprofloxacin-resistant bacteria in soil amended with manure.201627847506
384750.9998The impact and mechanism of quaternary ammonium compounds on the transmission of antibiotic resistance genes. The emergence of antibiotic resistance genes (ARGs) in microbes can be largely attributed to the abuse and misuse of antibiotics and biocides. Quaternary ammonium compounds (QACs) have been used worldwide as common disinfectants and detergents; however, their potential impact on the spread and diffusion of ARGs is still unknown. In this study, we detected the QAC resistance gene (qacEΔ1), the 1 integron gene (intI1), and 12 ARGs (sul1, sul2, cfr, cml, fexA, tetA, tetG, tetQ, tetX, ermB, bla(TEM,) and dfrA1) in 48 water samples from three watersheds by quantitative PCR (qPCR). We investigated the evolution of bacterial antibiotic resistance under QAC and antibiotic environmental pressures by long-term continuous culture. In addition, five QACs were selected to investigate the effect of QAC on the efficiency of conjugation transfer. The changes in bacterial cell membrane and production of reactive oxygen species (ROS) were detected by flow cytometry, revealing the mechanism by which QAC affects the spread of antibiotic resistance. Our results showed that the QAC resistance gene was ubiquitous in watersheds and it had significant correlation with intI1 and seven ARGs (r = 0.999, p < 0.01). QACs could increase the resistance of bacteria to multiple antibiotics. Furthermore, all five QACs promoted the conjugation transfer of the RP4 plasmid; the optimal concentration of QACs was about 10(-1)-10(-2) mg/L and their transfer efficiencies were between 1.33 × 10(-6) and 8.87 × 10(-5). QACs enhanced membrane permeability of bacterial cells and stimulated bacteria to produce ROS, which potentially promoted the transfer of plasmids between bacteria. In conclusion, this study demonstrated that QACs may facilitate the evolution and gene transfer of antibiotic resistance gene among microbiome.201931372954
343760.9998Characteristics of ARG-carrying plasmidome in the cultivable microbial community from wastewater treatment system under high oxytetracycline concentration. Studies on antibiotic production wastewater have shown that even a single antibiotic can select for multidrug resistant bacteria in aquatic environments. It is speculated that plasmids are an important mechanism of multidrug resistance (MDR) under high concentrations of antibiotics. Herein, two metagenomic libraries were constructed with plasmid DNA extracted from cultivable microbial communities in a biological wastewater treatment reactor supplemented with 0 (CONTROL) or 25 mg/L of oxytetracycline (OTC-25). The OTC-25 plasmidome reads were assigned to 72 antibiotic resistance genes (ARGs) conferring resistance to 13 types of antibiotics. Dominant ARGs, encoding resistance to tetracycline, aminoglycoside, sulfonamide, and multidrug resistance genes, were enriched in the plasmidome under 25 mg/L of oxytetracycline. Furthermore, 17 contiguous multiple-ARG carrying contigs (carrying ≥ 2 ARGs) were discovered in the OTC-25 plasmidome, whereas only nine were found in the CONTROL. Mapping of the OTC-25 plasmidome reads to completely sequenced plasmids revealed that the conjugative IncU resistance plasmid pFBAOT6 of Aeromonas caviae, carrying multidrug resistance transporter (pecM), tetracycline resistance genes (tetA, tetR), and transposase genes, might be a potential prevalent resistant plasmid in the OTC-25 plasmidome. Additionally, two novel resistant plasmids (containing contig C301682 carrying multidrug resistant operon mexCD-oprJ and contig C301632 carrying the tet36 and transposases genes) might also be potential prevalent resistant plasmids in the OTC-25 plasmidome. This study will be helpful to better understand the role of plasmids in the development of MDR in water environments under high antibiotic concentrations.201829332216
367870.9998Abundance 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
343280.9998Insights 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
719890.9998Abundance and distribution of antibiotic resistance genes in a full-scale anaerobic-aerobic system alternately treating ribostamycin, spiramycin and paromomycin production wastewater. The occurrence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) has been intensively investigated for wastewater treatment systems treating single class of antibiotic in recent years. However, the impacts of alternately occurring antibiotics in antibiotic production wastewater on the behavior of ARGs in biological treatment systems were not well understood yet. Herein, techniques including high-capacity quantitative PCR and quantitative PCR (qPCR) were used to investigate the behavior of ARGs in an anaerobic-aerobic full-scale system. The system alternately treated three kinds of antibiotic production wastewater including ribostamycin, spiramycin and paromomycin, which referred to stages 1, 2 and 3. The aminoglycoside ARGs (52.1-79.3%) determined using high-capacity quantitative PCR were the most abundant species in all sludge samples of the three stages. The total relative abundances of macrolide-lincosamide-streptogramin (MLS) resistance genes and aminoglycoside resistance genes measured using qPCR were significantly higher (P < 0.05) in aerobic sludge than in sewage sludge. However, the comparison of ARGs acquired from three alternate stages revealed that MLS genes and the aminoglycoside ARGs did not vary significantly (P > 0.05) in both aerobic and anaerobic sludge samples. In aerobic sludge, one acetyltransferase gene (aacA4) and the other three nucleotidyltransferase genes (aadB, aadA and aadE) exhibited positive correlations with intI1 (r (2) = 0.83-0.94; P < 0.05), implying the significance of horizontal transfer in their proliferation. These results and facts will be helpful to understand the abundance and distribution of ARGs from antibiotic production wastewater treatment systems.201728551881
7197100.9998The response of copper resistance genes, antibiotic resistance genes, and intl1/2 to copper addition during anaerobic digestion in laboratory. Heavy metal pollution can serve as a selective pressure for antibiotic resistance genes in polluted environments. Anaerobic fermentation, as a recommended wastewater treatment method, is an effective mitigation measure of antibiotic resistance diffusion. To explore the influence of copper on anaerobic fermentation, we exposed the fermentation substrate to copper in a laboratory setup. We found that the relative abundance of 8 genes (pcoD, tetT, tetA, tetB, tetO, qnrS, ermA and ermB) increased at the late stage of fermentation and their abundance was linked to copper content. Corynebacterium and Streptococcus were significantly positively correlated with ermA, ermB, tetA and tetB (P < 0.05). The relative abundance of tetT was significantly positively correlated with Terrisporobacter, Clostridium_sensu_stricto_1 and Turicibacter (P < 0.05). We screened 90 strains of copper resistant bacteria from blank, medium and high copper test groups on days 25, 31 and 37. The number of fragments carried by a single strain increased with time while intl1, ermA and ermB existed in almost all combinations of the multiple fragments we identified. The relative abundance of these three genes were linearly correlated with Corynebacterium and Streptococcus. The antibiotic resistance genes carried by class 1 integrons gradually increased with time in the fermentation system and integrons carrying ermA and ermB most likely contributed to host survival through the late stages of fermentation. The genera Corynebacterium and Streptococcus may be the primary carriers of such integrated mobile gene element and this was most likely the reason for their rebound in relative abundance during the late fermentation stages.202133418156
5355110.9998Impact of wastewater treatment processes on antimicrobial resistance genes and their co-occurrence with virulence genes in Escherichia coli. An increase in the frequency of antimicrobial resistance genes (ARGs) in bacteria including Escherichia coli could be a threat to public health. This study investigated the impact of activated sludge and physicochemical wastewater treatment processes on the prevalence of ARGs in E. coli isolates. In total, 719 E. coli were isolated from the influent and effluent (prior to disinfection) of two activated sludge and two physicochemical municipal treatment plants, and genotyped using DNA microarrays. Changes in the abundance of ARGs in the E. coli population were different for the two treatment processes. Activated sludge treatment did not change the prevalence of ARG-possessing E. coli but increased the abundance of ARGs in the E. coli genome while physicochemical treatment reduced both the prevalence of ARG-carrying E. coli as well as the frequency of ARGs in the E. coli genome. Most E. coli isolates from the four treatment plants possessed ARGs of multiple antimicrobial classes, mainly aminoglycoside, β-lactams, quinolone and tetracyclines. In addition these isolates harboured DNA insertion sequence elements including integrase and transposase. A significant positive association was found between the occurrence of ARGs and virulence genotypes.201424380739
7123120.9998Presence 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
3553130.9998Genetic redundancy and persistence of plasmid-mediated trimethoprim/sulfamethoxazole resistant effluent and stream water Escherichia coli. Antibiotic resistant bacteria may persist in effluent receiving surface water in the presence of low (sub-inhibitory) antibiotic concentrations if the bacteria possess multiple genes encoding resistance to the same antibiotic. This redundancy of antibiotic resistance genes may occur in plasmids harboring conjugation and mobilization (mob) and integrase (intI) genes. Plasmids extracted from 76 sulfamethoxazole-trimethoprim resistant Escherichia coli originally isolated from effluent and an effluent-receiving stream were used as DNA template to identify sulfamethoxazole (sul) and trimethoprim (dfr) resistances genes plus detect the presence of intI and mob genes using PCR. Sulfamethoxazole and trimethoprim resistance was plasmid-mediated with three sul (sul1, sul2 and sul3 genes) and four dfr genes (dfrA12, dfrA8, dfrA17, and dfrA1 gene) the most prevalently detected. Approximately half of the plasmids carried class 1 and/or 2 integron and, although unrelated, half were also transmissible. Sampling site in relationship to effluent input significantly affected the number of intI and mob but not the number of sul and dfr genes. In the presence of low (sub-inhibitory) sulfamethoxazole concentration, isolates persisted regardless of integron and mobilization gene designation, whereas in the presence of trimethoprim, the presence of both integron and mobilization genes made isolates less persistent than in the absence of both or the presence of a gene from either group individually. Regardless, isolates persisted in large concentrations throughout the experiment. Treated effluent containing antibiotic resistant bacteria may be an important source of integrase and mobilization genes into the stream environment. Sulfamethoxazole-trimethoprim resistant bacteria may have a high degree of genetic redundancy and diversity carrying resistance to each antibiotic, although the role of integrase and mobilization genes towards persistence is unclear.201627455416
3422140.9998Exploring the Role of Coliform Bacteria in Class 1 Integron Carriage and Biofilm Formation During Drinking Water Treatment. This study investigates the role of coliforms in the carriage of class 1 integron and biocide resistance genes in a drinking water treatment plant and explores the relationship between the carriage of such genes and the biofouling abilities of the strain. The high incidence of class 1 integron and biocide resistance genes (33.3 % of the isolates) highlights the inherent risk of genetic contamination posed by coliform populations during drinking water treatment. The association between the presence of intI1 gene and qac gene cassettes, especially qacH, was greater in biofilm cells. In coliforms recovered from biofilms, a higher frequency of class 1 integron elements and higher diversity of genetic patterns occurred, compared to planktonic cells. The coliform isolates under the study proved to mostly carry non-classical class 1 integrons lacking the typical qacEΔ1/sul1 genes or a complete tni module, but bearing the qacH gene. No link was found between the carriage of integron genes and the biofouling degree of the strain, neither in aerobic or in anaerobic conditions. Coliform bacteria isolated from established biofilms rather adhere in oxygen depleted environments, while the colonization ability of planktonic cells is not significantly affected by oxygen availability.201627079455
3520150.9998Influence 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
3676160.9998Diversity of antibiotic resistance genes and encoding ribosomal protection proteins gene in livestock waste polluted environment. The rapid development and increase of antibiotic resistance are global phenomena resulting from the extensive use of antibiotics in human clinics and animal feeding operations. Antibiotics can promote the occurrence of antibiotic resistance genes (ARGs), which can be transferred horizontally to humans and animals through water and the food chain. In this study, the presence and abundance of ARGs in livestock waste was monitored by quantitative PCR. A diverse set of bacteria and tetracycline resistance genes encoding ribosomal protection proteins (RPPs) from three livestock farms and a river were analyzed through denaturing gradient gel electrophoresis (DGGE). The abundance of sul(I) was 10(3) to 10(5) orders of magnitude higher than that of sul(II). Among 11 tet-ARGs, the most abundant was tet(O). The results regarding bacterial diversity indicated that the presence of antibiotics might have an evident impact on bacterial diversity at every site, particularly at the investigated swine producer. The effect of livestock waste on the bacterial diversity of soil was stronger than that of water. Furthermore, a sequencing analysis showed that tet(M) exhibited two genotypes, while the other RPPs-encoding genes exhibited at least three genotypes. This study showed that various ARGs and RPPs-encoding genes are particularly widespread among livestock.201829469609
3139170.9998Sulfonamide-resistant bacteria and their resistance genes in soils fertilized with manures from Jiangsu Province, Southeastern China. Antibiotic-resistant bacteria and genes are recognized as new environmental pollutants that warrant special concern. There were few reports on veterinary antibiotic-resistant bacteria and genes in China. This work systematically analyzed the prevalence and distribution of sulfonamide resistance genes in soils from the environments around poultry and livestock farms in Jiangsu Province, Southeastern China. The results showed that the animal manure application made the spread and abundance of antibiotic resistance genes (ARGs) increasingly in the soil. The frequency of sulfonamide resistance genes was sul1 > sul2 > sul3 in pig-manured soil DNA and sul2 > sul1 > sul3 in chicken-manured soil DNA. Further analysis suggested that the frequency distribution of the sul genes in the genomic DNA and plasmids of the SR isolates from manured soil was sul2 > sul1 > sul3 overall (p<0.05). The combination of sul1 and sul2 was the most frequent, and the co-existence of sul1 and sul3 was not found either in the genomic DNA or plasmids. The sample type, animal type and sampling time can influence the prevalence and distribution pattern of sulfonamide resistance genes. The present study also indicated that Bacillus, Pseudomonas and Shigella were the most prevalent sul-positive genera in the soil, suggesting a potential human health risk. The above results could be important in the evaluation of antibiotic-resistant bacteria and genes from manure as sources of agricultural soil pollution; the results also demonstrate the necessity and urgency of the regulation and supervision of veterinary antibiotics in China.201425405870
7784180.9998No evidential correlation between veterinary antibiotic degradation ability and resistance genes in microorganisms during the biodegradation of doxycycline. Biodegradation of antibiotic residues in the environment by microorganisms may lead to the generation of antibiotic resistance genes (ARGs), which are of great concern to human health. The aim of this study was to determine whether there is a relationship between the ability to degrade antibiotic doxycycline (DOX) and the development of resistance genes in microorganisms. We isolated and identified ten bacterial strains from a vegetable field that had received long-term manure application as fertilizer and were capable of surviving in a series of DOX concentrations (25, 50, 80, and 100mg/L). Our results showed no evidential correlation between DOX degradation ability and the development of resistance genes among the isolated microorganisms that had high DOX degradation capability (P > 0.05). This was based on the fact that Escherichia sp. and Candida sp. were the most efficient bacterial strains to degrade DOX (92.52% and 91.63%, respectively), but their tetracycline resistance genes showed a relatively low risk of antibiotic resistance in a 7-day experiment. Moreover, the tetM of the ribosomal protection protein genes carried by these two preponderant bacteria was five-fold higher than that carried by other isolates (P < 0.05). Pearson correlations between the C(t)/C(0) of DOX and tet resistance genes of three isolates, except for Escherichia sp. and Candida sp., showed remarkable negative correlations (P < 0.05), mainly because tetG markedly increased during the DOX degradation process. Our results concluded that the biodegradation of antibiotic residues may not necessarily lead to the development of ARGs in the environment. In addition, the two bacteria that we isolated, namely, Escherichia sp. and Candida sp., are potential candidates for the engineering of environmentally friendly bacteria.201828942279
3331190.9998Impact of Wastewater Treatment on the Prevalence of Integrons and the Genetic Diversity of Integron Gene Cassettes. The integron platform allows the acquisition, expression, and dissemination of antibiotic resistance genes within gene cassettes. Wastewater treatment plants (WWTPs) contain abundant resistance genes; however, knowledge about the impacts of wastewater treatment on integrons and their gene cassettes is limited. In this study, by using clone library analysis and high-throughput sequencing, we investigated the abundance of class 1, 2, and 3 integrons and their corresponding gene cassettes in three urban WWTPs. Our results showed that class 1 integrons were most abundant in WWTPs and that wastewater treatment significantly reduced the abundance of all integrons. The WWTP influents harbored the highest diversity of class 1 integron gene cassettes, whereas class 3 integron gene cassettes exhibited highest diversity in activated sludge. Most of the gene cassette arrays detected in class 1 integrons were novel. Aminoglycoside, beta-lactam, and trimethoprim resistance genes were highly prevalent in class 1 integron gene cassettes, while class 3 integrons mainly carried beta-lactam resistance gene cassettes. A core class 1 integron resistance gene cassette pool persisted during wastewater treatment, implying that these resistance genes could have high potential to spread into environments through WWTPs. These data provide new insights into the impact of wastewater treatment on integron pools and highlight the need for surveillance of resistance genes within both class 1 and 3 integrons.IMPORTANCE Wastewater treatment plants represent a significant sink and transport medium for antibiotic resistance bacteria and genes spreading into environments. Integrons are important genetic elements involved in the evolution of antibiotic resistance. To better understand the impact of wastewater treatment on integrons and their gene cassette contexts, we conducted clone library construction and high-throughput sequencing to analyze gene cassette contexts for class 1 and class 3 integrons during the wastewater treatment process. This study comprehensively profiled the distribution of integrons and their gene cassettes (especially class 3 integrons) in influents, activated sludge, and effluents of conventional municipal wastewater treatment plants. We further demonstrated that while wastewater treatment significantly reduced the abundance of integrons and the diversity of associated gene cassettes, a large fraction of integrons persisted in wastewater effluents and were consequentially discharged into downstream natural environments.201829475864