Minimum influent concentrations of oxytetracycline, streptomycin and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems. - Related Documents




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719901.0000Minimum influent concentrations of oxytetracycline, streptomycin and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems. It has been demonstrated that antibiotic resistance could be induced and selected under high antibiotic concentrations in biological wastewater treatment systems. However, little is available regarding the minimum concentrations of antibiotics for selecting antibiotic resistance during wastewater treatment. Herein, the minimum influent concentrations of oxytetracycline, streptomycin, and spiramycin in selecting antibiotic resistance in biofilm type wastewater treatment systems were investigated by spiking respective antibiotic into wastewater with an antibiotic dose increasing from 0 to 0.1, 1, 5, 25, 50 mg/L stepwise over a period of 606 days. Significant increase (p < .01) in the total abundance of antibiotic resistance genes was observed for both streptomycin and oxytetracycline at a dose of 0.1 mg/L according to metagenomic sequencing, while the concentration levels leading to significant increases (p < .05) in resistant bacteria ratio were higher: 5 mg/L for streptomycin and 25 mg/L for oxytetracycline. Although resistome abundance increased with the increase of spiramycin dose, neither the corresponding Macrolide-Lincosamide-Streptogramin (MLS) resistance genes nor the resistant bacteria ratio showed perceptible increase. Partial canonical correspondence analysis showed that both bacterial community shift and mobile genetic elements alteration contributed to the enrichment of resistomes under the presence of streptomycin and oxytetracycline. Regarding spiramycin which is mainly targeting on Gram-positive bacteria, the dominance of the intrinsically resisting Gram-negative bacteria in the biofilm microbiota might be responsible for the vague change of MLS resistant determinants under the spiramycin stress. The results demonstrated that it is possible to prevent the development of antibiotic resistance during wastewater treatment by controlling the influent streptomycin and oxytetracyline concentrations below 0.1 mg/L. This work proposed an actionable approach for the management of antibiotic production wastewater.202032325576
343210.9999Insights 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
720120.9999Evolution of microbial community and drug resistance during enrichment of tetracycline-degrading bacteria. Recently, the microbial degradation of tetracycline has been widely reported. However, its potential risks in treating wastewater containing high concentrations of tetracycline have not been fully evaluated. In this study, the evolution of the microbial community and drug resistance was traced during the enrichment of tetracycline-degrading bacteria. The results showed that some minor compositions such as Shewanella, Bacillus, and Pseudomonas in the seed sludge became the predominant genera in the enrichment cultures when continuously using tetracycline as the sole carbon source, especially some possible pathogenic bacteria increased significantly in this process. The abundances of most TRGs/16S rDNA were increased after enrichment, although the relative abundance of tetA and tetL genes decreased to some extent. From the enrichment culture, 7 predominant tetracycline-degrading strains were isolated, of which TD-1 (Bacillus) and TD-5 (Shewanella) presented high degradation efficiencies (6-day degradation rate > 95%, half-life period of tetracycline ≈ 24 h). In addition, multiple TRGs, mobile genetic elements (MGEs) and even gene cassettes were found in each tetracycline-degrading isolate. The findings suggested that some risks such as the pathogenicity of isolates and the spread of ARGs should be considered when the biodegradation method is used to treat wastewater polluted with high concentrations of tetracycline.201930660087
719130.9998The impact of antimicrobials on the efficiency of methane fermentation of sewage sludge, changes in microbial biodiversity and the spread of antibiotic resistance. The study was designed to simultaneously evaluate the influence of high doses (512-1024 µg/g) the most commonly prescribed antimicrobials on the efficiency of anaerobic digestion of sewage sludge, qualitative and quantitative changes in microbial consortia responsible for the fermentation process, the presence of methanogenic microorganisms, and the fate of antibiotic resistance genes (ARGs). The efficiency of antibiotic degradation during anaerobic treatment was also determined. Metronidazole, amoxicillin and ciprofloxacin exerted the greatest effect on methane fermentation by decreasing its efficiency. Metronidazole, amoxicillin, cefuroxime and sulfamethoxazole were degraded in 100%, whereas ciprofloxacin and nalidixic acid were least susceptible to degradation. The most extensive changes in the structure of digestate microbiota were observed in sewage sludge exposed to metronidazole, where a decrease in the percentage of bacteria of the phylum Bacteroidetes led to an increase in the proportions of bacteria of the phyla Firmicutes and Proteobacteria. The results of the analysis examining changes in the concentration of the functional methanogen gene (mcrA) did not reflect the actual efficiency of methane fermentation. In sewage sludge exposed to antimicrobials, a significant increase was noted in the concentrations of β-lactam, tetracycline and fluoroquinolone ARGs and integrase genes, but selective pressure was not specific to the corresponding ARGs.202133831706
719040.9998Dynamics of microbial community and tetracycline resistance genes in biological nutrient removal process. The occurrence of antibiotics in wastewater has become a serious concern due to the possible development of antibiotic resistant bacteria in wastewater treatment process. In order to understand the dynamics of microbial community and tetracycline resistance genes in biological nutrient removal (BNR) process, three lab-scale sequencing batch reactors (SBRs) were operated under the stress of tetracycline. Results indicated that microbial community structure was altered, and tetracycline efflux pump genes were enhanced over 150-day operation in the presence of trace tetracycline of 20 and 50 μg L(-1), respectively. Furthermore, when the initial tetracycline concentrations were increased to 2 and 5 mg L(-1), substantial enhancement of tetracycline resistance was observed, accompanied with a sharp shift in microbial community structure. In this study, horizontal gene transfer was found to be the main mechanism for the development of tetracycline resistance genes under the long-terms stress of trace tetracycline. About 90.34% of the observed variations in tetracycline resistance genes could be explained by the dynamics of potential hosts of tetracycline resistance genes and class 1 integron. It should be noticed that the functional bacteria (e.g. Nitrospira, Dechloromonas, Rhodobacter and Candidatus_Accumulibacter) responsible for nutrient removal were positively correlated with tetracycline resistance, which might promote the prevalence of tetracycline resistance during biological wastewater treatment. Consequently, this study provided in-depth insights into the occurrence and prevalence of tetracycline resistance genes and their microbial hosts in BNR process.201930849601
343350.9998Effect of subinhibitory concentrations on the spreading of the ampicillin resistance gene bla(CMY-2) in an activated sludge microcosm. As the problem of multi-resistant bacteria grows a better understanding of the spread of antibiotic resistance genes is of utmost importance for society. Wastewater treatment plants contain subinhibitory concentrations of antibiotics and are thought to be hotspots for antibiotic resistance gene propagation. Here we evaluate the influence of sub-minimum inhibitory concentrations of antibiotics on the spread of resistance genes within the bacterial community in activated sludge laboratory-scale sequencing batch reactors. The mixed communities were fed two different ampicillin concentrations (500 and 5000 µg/L) and the reactors were run and monitored for 30 days. During the experiment the β-lactamase resistance gene bla(CMY-2) was monitored via qPCR and DNA samples were taken to monitor the effect of ampicillin on the microbial community. The relative copy number of bla(CMY-2) in the reactor fed with the sub-minimum inhibitory concentration of 500 µg/L ampicillin was spread out over a wider range of values than the control and 5000 µg/L ampicillin reactors indicating more variability of gene number in the 500 µg/L reactor. This result emphasises the problem of sub-minimum inhibitory concentrations of antibiotics in wastewater. High-throughput sequencing showed that continuous exposure to ampicillin caused a shift from a Bacteroidetes to Proteobacteria in the bacterial community. The combined use of qPCR and high-throughput sequencing showed that ampicillin stimulates the spread of resistance genes and leads to the propagation of microbial populations which are resistant to it.202539215485
719760.9998The 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
712370.9998Presence 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
712480.9998Changes in diversity of cultured bacteria resistant to erythromycin and tetracycline in swine manure during simulated composting and lagoon storage. This study investigated the impact of composting and lagoon storage on survival and change in diversity of tetracycline-resistant (Tc(r) ) and erythromycin-resistant (Em(r) ) bacteria and the resistance genes they carry in swine manure. Treatments were arranged as a 2 × 2 factorial design: composting vs lagoon storage and 0 vs 1% Surround WP Crop Protectant (a clay product) in three replicates. After 48 days of treatments, resistant bacteria were enumerated by selective plating and identified by 16S rRNA gene sequencing. The erm and the tet gene(s) carried by the resistant isolates were screened using class-specific PCR assays. The plate counts of Tc(r) and Em(r) bacteria decreased by 4-7 logs by composting, but only by 1-2 logs by the lagoon treatment. During the treatments, Acinetobacter gave way to Pseudomonas and Providencia as the largest resistant genera. The clay product had little effect on survival or diversity of resistant bacteria. Of six classes of erm and seven classes of tet genes tested, changes in prevalence were also noted. The results indicate that composting can dramatically shift Tc(r) and Em(r) bacterial populations, and composting can be an effective and practical approach to decrease dissemination of antibiotic resistance from swine farms to the environment. SIGNIFICANCE AND IMPACT OF THE STUDY: The presented research provided evidence that composting is much more effective than lagoon storage in dramatically decreasing culturable bacteria resistant to erythromycin and tetracycline in swine manure. Considerable diversity changes of resistant bacteria were also demonstrated during composting or lagoon storage. Overall, Acinetobacter was the major resistant genus in untreated swine manure, but pseudomonads and Providencia became the major resistant genera after the treatments. This is the first study that investigated diversity changes of cultured bacteria resistant to these two antibiotics during composting and lagoon storage of swine manure. New genes encoding resistance to the two antibiotics were also implied in the cultured isolates.201526031793
720090.9998Plant Growth, Antibiotic Uptake, and Prevalence of Antibiotic Resistance in an Endophytic System of Pakchoi under Antibiotic Exposure. Antibiotic contamination in agroecosystems may cause serious problems, such as the proliferation of various antibiotic resistant bacteria and the spreading of antibiotic resistance genes (ARGs) in the environment or even to human beings. However, it is unclear whether environmental antibiotics, antibiotic resistant bacteria, and ARGs can directly enter into, or occur in, the endophytic systems of plants exposed to pollutants. In this study, a hydroponic experiment exposing pakchoi (Brassica chinensis L.) to tetracycline, cephalexin, and sulfamethoxazole at 50% minimum inhibitory concentration (MIC) levels and MIC levels, respectively, was conducted to explore plant growth, antibiotic uptake, and the development of antibiotic resistance in endophytic systems. The three antibiotics promoted pakchoi growth at 50% MIC values. Target antibiotics at concentrations ranging from 6.9 to 48.1 µg·kg(-1) were detected in the treated vegetables. Additionally, the rates of antibiotic-resistant endophytic bacteria to total cultivable endophytic bacteria significantly increased as the antibiotics accumulated in the plants. The detection and quantification of ARGs indicated that four types, tetX, bla(CTX-M), and sul1 and sul2, which correspond to tetracycline, cephalexin, and sulfamethoxazole resistance, respectively, were present in the pakchoi endophytic system and increased with the antibiotic concentrations. The results highlight a potential risk of the development and spread of antibiotic resistance in vegetable endophytic systems.201729099753
7801100.9998Disinfection of swine wastewater using chlorine, ultraviolet light and ozone. Veterinary antibiotics are widely used at concentrated animal feeding operations (CAFOs) to prevent disease and promote growth of livestock. However, the majority of antibiotics are excreted from animals in urine, feces, and manure. Consequently, the lagoons used to store these wastes can act as reservoirs of antibiotics and antibiotic-resistant bacteria. There is currently no regulation or control of these systems to prevent the spread of these bacteria and their genes for antibiotic resistance into other environments. This study was conducted to determine the disinfection potential of chlorine, ultraviolet light and ozone against swine lagoon bacteria. Results indicate that a chlorine dose of 30 mg/L could achieve a 2.2-3.4 log bacteria reduction in lagoon samples. However, increasing the dose of chlorine did not significantly enhance the disinfection activity due to the presence of chlorine-resistant bacteria. The chlorine resistant bacteria were identified to be closely related to Bacillus subtilis and Bacillus licheniformis. A significant percentage of lagoon bacteria were not susceptible to the four selected antibiotics: chlortetracycline, lincomycin, sulfamethazine and tetracycline (TET). However, the presence of both chlorine and TET could inactivate all bacteria in one lagoon sample. The disinfection potential of UV irradiation and ozone was also examined. Ultraviolet light was an effective bacterial disinfectant, but was unlikely to be economically viable due to its high energy requirements. At an ozone dose of 100 mg/L, the bacteria inactivation efficiency could reach 3.3-3.9 log.200616678233
7193110.9998Plasmid-mediated transfer of antibiotic resistance genes and biofilm formation in a simulated drinking water distribution system under chlorine pressure. The effects of disinfectants and plasmid-based antibiotic resistance genes (ARGs) on the growth of microorganisms and the plasmid-mediated transfer of ARGs in the water and biofilm of the drinking water distribution system under simulated conditions were explored. The heterotrophic plate count of the water in reactors with 0.1 mg/L NaClO and NH(2)Cl was higher than in the control groups. There was no similar phenomenon in biofilm. In the water of reactors containing NaClO, the aphA and bla genes were lower than in the antibiotic resistant bacteria group, while both genes were higher in the water of reactors with NH(2)Cl than in the control group. Chloramine may promote the transfer of ARGs in the water phase. Both genes in the biofilm of the reactors containing chlorine were lower than the control group. Correlation analysis between ARGs and water quality parameters revealed that the copy numbers of the aphA gene were significantly positively correlated with the copy numbers of the bla gene in water and significantly negatively correlated in biofilm (p < 0.05). The results of the sequencing assay showed that bacteria in the biofilm, in the presence of disinfectant, were primarily Gram-negative. 1.0 mg/L chlorine decreased the diversity of the community in the biofilm. The relative abundance of some bacteria that may undergo transfer increased in the biofilm of the reactor containing 0.1 mg/L chlorine.202539617560
7298120.9998Chronic exposure to triclosan sustains microbial community shifts and alters antibiotic resistance gene levels in anaerobic digesters. Triclosan, an antimicrobial chemical found in consumer personal care products, has been shown to stimulate antibiotic resistance in pathogenic bacteria. Although many studies focus on antibiotic resistance pertinent to medical scenarios, resistance developed in natural and engineered environments is less studied and has become an emerging concern for human health. In this study, the impacts of chronic triclosan (TCS) exposure on antibiotic resistance genes (ARGs) and microbial community structure were assessed in lab-scale anaerobic digesters. TCS concentrations from below detection to 2500 mg kg(-1) dry solids were amended into anaerobic digesters over 110 days and acclimated for >3 solid retention time values. Four steady state TCS concentrations were chosen (30-2500 mg kg(-1)). Relative abundance of mexB, a gene coding for a component of a multidrug efflux pump, was significantly higher in all TCS-amended digesters (30 mg kg(-1) or higher) relative to the control. TCS selected for bacteria carrying tet(L) and against those carrying erm(F) at concentrations which inhibited digester function; the pH decrease associated with digester failure was suspected to cause this selection. Little to no impact of TCS was observed on intI1 relative abundance. Microbial communities were also surveyed by high-throughput 16S rRNA gene sequencing. Compared to the control digesters, significant shifts in community structure towards clades containing commensal and pathogenic bacteria were observed in digesters containing TCS. Based on these results, TCS should be included in studies and risk assessments that attempt to elucidate relationships between chemical stressors (e.g. antibiotics), antibiotic resistance genes, and public health.201627291499
7784130.9998No 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
3521140.9998Indirect 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
7189150.9998Comparative effects of different antibiotics on antibiotic resistance during swine manure composting. This study explored commonly-used antibiotics (lincomycin, chlorotetracycline, sulfamethoxazole, and ciprofloxacin) and their collective effects on antibiotic resistance during composting. In the first 7 days, ciprofloxacin showed the greatest influence on the physicochemical factors among the studied antibiotics; the removal of antibiotic resistance genes (ARGs) in the multiple-antibiotic treatment was significantly less than single-antibiotic treatments; especially, the largest removal of ribosomal protection genes (tetW and tetO) occurred in single ciprofloxacin treatment. In the end of composting, similar removal ratio (29.71-99.79%) of ARGs was achieved in different treatments (p greater than 0.05); Chloroflexi became the main phylum and it was closely associated with ARGs removal based on the network analysis. Potential host bacteria of ARGs varied with different antibiotics; in particular, the presence of multiple antibiotics increased potential host bacteria of ermA, sul1 and tetO. Above all, collective effects of different antibiotics led to the enrichment of antibiotic resistance in the composting.202032712514
7182160.9998Effects of UV disinfection on phenotypes and genotypes of antibiotic-resistant bacteria in secondary effluent from a municipal wastewater treatment plant. To elucidate the effects of UV disinfection on antibiotic resistance in biologically-treated wastewater, we investigated the antibiotic resistance profiles, species of cultivable heterotrophic bacteria, and antibiotic-resistance genes (ARGs) in antibiotic-resistant bacteria before and after treatment. UV disinfection greatly changed the bacterial community structure and the antibiotic resistance in wastewater. The antibiotic resistance in wastewater samples was strongly associated with the bacterial community. The proportions of Gram-positive bacteria gradually increased with increasing UV fluence. The proportions of bacteria resistant to cephalexin, penicillin, and vancomycin all greatly decreased after UV treatment in both sampling events (July 2018 and January 2019), and those for bacteria resistant to ofloxacin, ciprofloxacin, and sulfadiazine increased, resulting from the alternative antibiotic resistance profiles among different genera. UV disinfection induced the selection of multi-antibiotic resistant (MAR) bacteria. For example, the MAR indices of Aeromonas, the dominant genus during the treatments, were significantly increased after UV irradiation (P < 0.05). The MAR index was also markedly increased (P < 0.05) at a fluence of 5 mJ/cm(2) in both events. In UV10 treatment, the bacterial community structure was greatly changed. The genera with relatively low MAR indices replaced that with high MAR indices, and became the dominant genera. As a result, the MAR indices of treated samples showed a decreased trend after 10 mJ/cm(2) UV irradiation. The detection frequencies of ARGs located on the chromosome varied mainly due to the evolution of the microbial community. The occurrence of ARGs (tetA, tetC, tetM, tetW, tetX, and sul1) located on plasmid DNA decreased after UV disinfection, and the average detection frequencies of tet and sul genes decreased by 15% and 6%, respectively (P < 0.05). Generally speaking, the effect of UV disinfection on the enrichment of antibiotic resistance is limited in this study, and horizontal gene transfer via the plasmids in surviving bacteria might be impaired due to the decreased abundance of ARGs on the plasmids.201930991178
8031170.9998Anaerobic Digestion of Tetracycline Spiked Livestock Manure and Poultry Litter Increased the Abundances of Antibiotic and Heavy Metal Resistance Genes. Anaerobic digestion is used for the treatment of animal manure by generating biogas. Heavy metals cause environmental pollutions and co-select for antimicrobial resistance. We evaluated the impact of mesophilic anaerobic digestion of cattle manure (CM), swine manure (SM) and poultry litter (PL) on the concentrations of seven tetracycline [tet(A), tet(B), tet(G), tet(M), tet(O), tet(Q), and tet(W)], macrolide [erm(B)], methicillin (mecA and mecC), copper (copB, pcoA, pcoD, and tcrB) and zinc (czrC) resistance genes, and three bacterial species (E. coli, Enterococcus spp. and Staphylococcus aureus). The total bacterial population and total abundance of the seven tet genes significantly increased in the three manure types after digestion. Concentration of tet(M) was strongly correlated with that of erm(B) and enterococci. As concentration of tetracyclines declined during anaerobic digestion, that of four tet genes (A, B, Q, and W) and 16S rRNA increased, that of tet(M) decreased, and that of tet(G) and tet(O) did not change. Concentrations of copB and pcoA did not change; while that of pcoD did not change in the PL, it increased in the SM and CM. While the concentration of enterococci remained unchanged in CM, it significantly increased in the PL and SM. Concentrations of tcrB significantly increased in the three manure types. While concentrations of S. aureus significantly increased in the CM and PL, that of SM was not affected. Concentrations of mecC significantly increased in all manure types after digestion; while mecA concentrations did not change in the SM, they significantly increased in CM and PL. While concentration of czrC remained low in the CM, it increased in the PL but declined in the SM. In conclusion, while mesophilic anaerobic digestion of animal manure decreased concentration of tetracyclines, it increased the concentrations of total bacteria, tet genes, E. coli, enterococci and S. aureus and methicillin resistance genes. It did not have any effect on concentrations of heavy metals; concentrations of heavy metal resistance genes either increased or remained unaffected depending on the animal species. This study showed the need for post-digestion treatments of animal manure to remove bacteria, antibiotic resistance genes, heavy metals and their resistance genes.202033391245
7202180.9998Cyanobacterial extracellular antibacterial substances could promote the spread of antibiotic resistance: impacts and reasons. Many studies have shown that antibiotic resistance genes (ARGs) can be facilitated by a variety of antibacterial substances. Cyanobacteria are photosynthetic bacteria that are widely distributed in the ocean. Some extracellular substances produced by marine cyanobacteria have been found to possess antibacterial activity. However, the impact of these extracellular substances on ARGs is unclear. Therefore, we established groups of seawater microcosms that contained different concentrations (1000, 100, 10, 1, 0.1, 0.01, and 0 μg mL(-1)) of cyanobacterial extracellular substances (CES), and tracked the changes of 17 types of ARGs, the integron gene (intI1), as well as the bacterial community at different time points. The results showed that CES could enrich most ARGs (15/17) in the initial stage, particularly at low concentrations (10 and 100 μg mL(-1)). The correlation analysis showed a positive correlation between several ARGs and intI1. It is suggested that the abundance of intI1 increased with CES may contribute to the changes of these ARGs, and co-resistance of CES may be the underlying reason for the similar variation pattern of some ARGs. Moreover, the results of qPCR and high-throughput sequencing of 16S rRNA showed that CES had an inhibitory impact on the growth of bacterial communities. High concentrations of CES were found to alter the structure of bacterial communities. Co-occurrence networks showed that bacteria elevated in the high concentration group of CES and might serve as the potential hosts for a variety of ARGs. In general, marine cyanobacteria could play an important role in the global dissemination of ARGs and antibiotic-resistant bacteria (ARBs).202337947439
3520190.9998Influence 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