Effect of subinhibitory concentrations on the spreading of the ampicillin resistance gene bla(CMY-2) in an activated sludge microcosm. - Related Documents




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343301.0000Effect 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
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
368520.9999Selective concentration for ciprofloxacin resistance in Escherichia coli grown in complex aquatic bacterial biofilms. There is concern that antibiotics in the environment can select for and enrich bacteria carrying acquired antibiotic resistance genes, thus increasing the potential of those genes to emerge in a clinical context. A critical question for understanding and managing such risks is what levels of antibiotics are needed to select for resistance in complex bacterial communities. Here, we address this question by examining the phenotypic and genotypic profiles of aquatic communities exposed to ciprofloxacin, also evaluating the within-species selection of resistant E. coli in complex communities. The taxonomic composition was significantly altered at ciprofloxacin exposure concentrations down to 1 μg/L. Shotgun metagenomic analysis indicated that mobile quinolone resistance determinants (qnrD, qnrS and qnrB) were enriched as a direct consequence of ciprofloxacin exposure from 1 μg/L or higher. Only at 5-10 μg/L resistant E.coli increased relative to their sensitive counterparts. These resistant E. coli predominantly harbored non-transferrable, chromosomal triple mutations (gyrA S83 L, D87N and parC S80I), which confer high-level resistance. In a controlled experimental setup such as this, we interpret effects on taxonomic composition and enrichment of mobile quinolone resistance genes as relevant indicators of risk. Hence, the lowest observed effect concentration for resistance selection in complex communities by ciprofloxacin was 1 μg/L and the corresponding no observed effect concentration 0.1 μg/L. These findings can be used to define and implement discharge or surface water limits to reduce risks for selection of antibiotic resistance in the environment.201829704804
343030.9999Benzalkonium chloride alters phenotypic and genotypic antibiotic resistance profiles in a source water used for drinking water treatment. Antibiotic resistance is a major public health concern. Triclosan is an antimicrobial compound with direct links to antibiotic resistance that was widely used in soaps in the U.S. until its ban by the U.S. Food and Drug Administration. Benzalkonium chloride (BAC), a quaternary ammonium compound, has widely replaced triclosan in soaps marketed as an antibacterial. BAC has been detected in surface waters and its presence will likely increase following increased use in soap products. The objective of this study was to determine the effect of BAC on relative abundance of antibiotic resistance in a bacterial community from a surface water used as a source for drinking water treatment. Bench-scale microcosm experiments were conducted with microbial communities amended with BAC at concentrations ranging from 0.1 μg L(-1) to 500 μg L(-1). Phenotypic antibiotic resistance was quantified by culturing bacteria in the presence of different antibiotics, and genotypic resistance was determined using qPCR to quantify antibiotic resistance genes (ARGs). BAC at concentrations ranging from 0.1 μg L(-1) to 500 μg L(-1) was found to positively select for bacteria resistant to ciprofloxacin and sulfamethoxazole, and negatively select against bacteria with resistance to six other antibiotics. Exposure to BAC for 14 days increased the relative abundance of sul1 and bla(TEM). This study re-highlights the importance of employing both culture and non-culture-based techniques to identify selection for antibiotic resistance. The widespread use of BAC will likely impact antibiotic resistance profiles of bacteria in the environment, including in source waters used for drinking water, wastewater treatment plants, and natural waterways.202031767233
532640.9999The presence of antibiotic-resistant bacteria at four Norwegian wastewater treatment plants: seasonal and wastewater-source effects. Wastewater treatment plants receive low concentrations of antibiotics. Residual concentrations of antibiotics in the effluent may accelerate the development of antibiotic resistance in the receiving environments. Monitoring of antimicrobial resistance genes (ARGs) in countries with strict regulation of antibiotic use is important in gaining knowledge of how effective these policies are in preventing the emergence of ARGs or whether other strategies are required, for example, at-source treatment of hospital effluents. This study evaluates the presence of certain common resistance genes (bla (SHV-1), bla (TEM-1), msrA, ermA, ermC, tetM, tetL, tetA, vanA, and vanC) in the influent, sludge, and effluent of four wastewater treatment plants (WWTPs) in the North Jæren region of Norway at two different sampling times (January and May). These WWTPs vary in drainage area and wastewater composition and were selected based on their differing wastewater characteristics. Randomly selected colonies from the activated sludge samples were used to determine the minimum inhibitory concentration (MIC) for ampicillin, vancomycin, and tetracycline. In addition, variations in the bacterial composition of the wastewater were characterized via 16S rRNA sequencing and were analyzed in terms of bacterial host taxa that explain the presence of the ARGs in wastewater. The MIC tests revealed MIC(90) values of >128 µg/mL for ampicillin, ≥128 µg/mL for vancomycin, and 32 µg/mL for tetracycline. In addition, the three resistance genes, ermB, tetA, and tetM, that were present in the influent and activated sludge were still present in the effluent. These results indicate that WWTPs represent a direct route into the environment for resistance genes and do not significantly reduce their abundance. Hence, the development of treatment methods for the removal of these genes from WWTPs in the future is of utmost importance.202439816252
368450.9999Minimal selective concentrations of tetracycline in complex aquatic bacterial biofilms. Selection pressure generated by antibiotics released into the environment could enrich for antibiotic resistance genes and antibiotic resistant bacteria, thereby increasing the risk for transmission to humans and animals. Tetracyclines comprise an antibiotic class of great importance to both human and animal health. Accordingly, residues of tetracycline are commonly detected in aquatic environments. To assess if tetracycline pollution in aquatic environments promotes development of resistance, we determined minimal selective concentrations (MSCs) in biofilms of complex aquatic bacterial communities using both phenotypic and genotypic assays. Tetracycline significantly increased the relative abundance of resistant bacteria at 10 μg/L, while specific tet genes (tetA and tetG) increased significantly at the lowest concentration tested (1 μg/L). Taxonomic composition of the biofilm communities was altered with increasing tetracycline concentrations. Metagenomic analysis revealed a concurrent increase of several tet genes and a range of other genes providing resistance to different classes of antibiotics (e.g. cmlA, floR, sul1, and mphA), indicating potential for co-selection. Consequently, MSCs for the tet genes of ≤ 1 μg/L suggests that current exposure levels in e.g. sewage treatment plants could be sufficient to promote resistance. The methodology used here to assess MSCs could be applied in risk assessment of other antibiotics as well.201626938321
529360.9999Tetracycline-Resistant Bacteria Selected from Water and Zebrafish after Antibiotic Exposure. The emergence of antibiotic-resistant pathogens due to worldwide antibiotic use is raising concern in several settings, including aquaculture. In this work, the selection of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) was evaluated after exposure of zebrafish to oxytetracycline (OTC) for two months, followed by a recovery period. The selection of ARB in water and fish was determined using selective media. The abundance of tetA genes was estimated through qPCR. Higher prevalence of ARB was measured in all samples exposed to the antibiotic when compared to control samples, although statistical significance was only achieved five days after exposure. Isolates recovered from samples exposed to the antibiotic were affiliated with Pseudomonas and Stenotrophomonas. Various antibiotic susceptibility profiles were detected and 37% of the isolates displayed multidrug resistance (MDR). The selection of the tetA gene was confirmed by qPCR at the highest OTC concentration tested. Two MDR isolates, tested using zebrafish embryos, caused significant mortality, indicating a potential impact on fish health and survival. Overall, our work highlights the potential impact of antibiotic contamination in the selection of potential pathogenic ARB and ARGS.202133804606
384470.9999Effects of Nutrient Level and Growth Rate on the Conjugation Process That Transfers Mobile Antibiotic Resistance Genes in Continuous Cultures. Bacteria in the effluent of wastewater treatment plants (WWTPs) can transfer antibiotic resistance genes (ARGs) to the bacteria in receiving water through conjugation; however, there is a lack of quantitative assessment of this phenomenon in continuous cultures. Our objective was to determine the effects of background nutrient levels in river water column and growth rates of bacteria on the conjugation frequency of ARGs from effluent bacteria to river bacteria, as well as on the resulting resistance level (i.e., MICs) of the river bacteria. Chemostats were employed to simulate the discharge points of WWTPs into rivers, where effluent bacteria (donor cells) meet river bacteria (recipient cells). Both donor and recipient cells were Escherichia coli cells, and the donor cells were constructed by filter mating with bacteria in the effluent of a local WWTP. Results showed that higher bacterial growth rate (0.45 h(-1) versus 0.15 h(-1)) led to higher conjugation frequencies (10(-4) versus 10(-6) transconjugant per recipient). The nutrient level also significantly affected the conjugation frequency, albeit to a lesser extent than the growth rate. The MIC against tetracycline increased from 2 mg/L in the recipient to 64 to 128 mg/L in transconjugants. In comparison, the MIC only increased to as high as 8 mg/L in mutants. Whole-genome sequencing showed that the tet-containing plasmid in both the donor and the transconjugant cells also occur in other fecal bacterial genera. The quantitative information obtained from this study can inform hazard identification related to the proliferation of wastewater-associated ARGs in surface water. IMPORTANCE WWTPs have been regarded as an important hot spot of ARGs. The discharge point of WWTP effluent, where ARGs may be horizontally transferred from bacteria of treated wastewater to bacteria of receiving water, is an important interface between the human-dominated ecosystem and the natural environment. The use of batch cultures in previous studies cannot adequately simulate the nutrient conditions and growth rates in receiving water. In this study, chemostats were employed to simulate the continuous growth of bacteria in receiving water. Furthermore, the experimental setup allowed for separate investigations on the effects of nutrient levels (i.e., simulating background nutrients in river water) and bacterial growth rates on conjugation frequencies and resulting resistance levels. The study generates statistically sound ecological data that can be used to estimate the risk of wastewater-originated ARGs as part of the One Health framework.202236094214
532580.9999Genes encoding tetracycline resistance in a full-scale municipal wastewater treatment plant investigated during one year. Tetracycline-resistant bacteria and genes encoding tetracycline resistance are common in anthropogenic environments. We studied how wastewater treatment affects the prevalence and concentration of two genes, tetA and tetB, that encode resistance to tetracycline. Using real-time polymerase chain reaction (PCR) we analysed wastewater samples collected monthly for one year at eight key-sites in a full-scale municipal wastewater treatment plant (WWTP). We detected tetA and tetB at each sampling site and the concentration of both genes, expressed per wastewater volume or per total-DNA, decreased over the treatment process. The reduction of tetA and tetB was partly the result of the sedimentation process. The ratio of tetA and tetB, respectively, to total DNA was lower in or after the biological processes. Taken together our data show that tetracycline resistance genes occur throughout the WWTP, and that the concentrations are reduced under conventional operational strategies.201020154388
712390.9999Presence 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
3847100.9999The 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
7800110.9999Effects of ultraviolet disinfection on antibiotic-resistant Escherichia coli from wastewater: inactivation, antibiotic resistance profiles and antibiotic resistance genes. AIMS: To evaluate the effect of ultraviolet (UV) disinfection on antibiotic-resistant Escherichia coli. METHODS AND RESULTS: Antibiotic-resistant E. coli strains were isolated from a wastewater treatment plant and subjected to UV disinfection. The effect of UV disinfection on the antibiotic resistance profiles and the antibiotic resistance genes (ARGs) of antibiotic-resistant E. coli was evaluated by a combination of antibiotic susceptibility analysis and molecular methods. Results indicated that multiple-antibiotic-resistant (MAR) E. coli were more resistant at low UV doses and required a higher UV dose (20 mJ cm(-2) ) to enter the tailing phase compared with those of antibiotic-sensitive E. coli (8 mJ cm(-2) ). UV disinfection caused a selective change in the inhibition zone diameters of surviving antibiotic-resistant E. coli and a slight damage to ARGs. The inhibition zone diameters of the strains resistant to antibiotics were more difficult to alter than those susceptible to antibiotics because of the existence and persistence of corresponding ARGs. CONCLUSIONS: The resistance of MAR bacteria to UV disinfection at low UV doses and the changes in inhibition zone diameters could potentially contribute to the selection of antibiotic-resistant bacteria in wastewater treatment after UV disinfection. The risk of spread of antibiotic resistance still exists owing to the persistence of ARGs. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study highlights the acquisition of other methods to control the spread of ARGs.201728459506
3676120.9999Diversity 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
3678130.9999Abundance 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
3681140.9999A closer look at the antibiotic-resistant bacterial community found in urban wastewater treatment systems. The conventional biological treatment process can provide a favorable environment for the maintenance and dissemination of antibiotic-resistant bacteria and the antibiotic resistance genes (ARG) they carry. This study investigated the occurrence of antibiotic resistance in three wastewater treatment plants (WWTP) to determine the role they play in the dissemination of ARGs. Bacterial isolates resistant to tetracycline were collected, and tested against eight antibiotics to determine their resistance profiles and the prevalence of multiple antibiotic resistance. It was found that bacteria resistant to tetracycline were more likely to display resistance to multiple antibiotics compared to those isolates that were not tetracycline resistant. Polymerase chain reaction (PCR) was used to identify the tetracycline resistance determinants present within the bacterial communities of the WWTPs and receiving waters, and it was found that ARGs may not be released from the treatment process. Identification of isolates showed that there was a large diversity of species in both the tetracycline-resistant and tetracycline-sensitive populations and that the two groups were significantly different in composition. Antibiotic resistance profiles of each population showed that a large diversity of resistance patterns existed within genera suggesting that transmission of ARG may progress by both horizontal gene and vertical proliferation.201829484827
7183150.9999Evaluation of five antibiotic resistance genes in wastewater treatment systems of swine farms by real-time PCR. Antibiotics are widely used in livestock for infection treatment and growth promotion. Wastes from animal husbandry are a potential environmental source of antibiotic-insensitive pathogens, and the removal efficiency of the resistance genotypes in current wastewater treatment plants (WWTPs) is unknown. In this study, quantitative PCR was used for evaluating antibiotic resistance genes in wastewater treatment processes. Six wastewater treatment plants in different swine farms were included in this study, and five antibiotic resistance genes (ARGs) were tested for each treatment procedure. All of the tested ARGs including tetA, tetW, sulI, sulII, and blaTEM genes were detected in six swine farms with considerable amounts. The results showed that antibiotic resistance is prevalent in livestock farming. The ARG levels were varied by wastewater treatment procedure, frequently with the highest level at anaerobic treatment tank and lowest in the activated sludge unit and the effluents. After normalizing the ARG levels to 16S rRNA gene copies, the results showed that ARGs in WWTP units fluctuated partly with the quantity of bacteria. Regardless of its importance in biodegradation, the anaerobic procedure may facilitate bacterial growth thus increasing the sustainability of the antibiotic resistance genotypes. After comparing the copy numbers in influx and efflux samples, the mean removal efficiency of ARGs ranged between 33.30 and 97.56%. The results suggested that treatments in the WWTP could partially reduce the spread of antibiotic-resistant bacteria, and additional procedures such as sedimentation may not critically affect the removal efficiency.201425064719
5291160.9999Low-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
3423170.9999bla(TEM) and vanA as indicator genes of antibiotic resistance contamination in a hospital-urban wastewater treatment plant system. Four indicator genes were monitored by quantitative PCR in hospital effluent (HE) and in the raw and treated wastewater of the municipal wastewater treatment plant receiving the hospital discharge. The indicator genes were the class 1 integrase gene intI1, to assess the capacity of bacteria to be involved in horizontal gene transfer processes; bla(TEM), one of the most widespread antibiotic resistance genes in the environment, associated with Enterobacteriaceae; vanA, an antibiotic resistance gene uncommon in the environment and frequent in clinical isolates; and marA, part of a locus related to the stress response in Enterobacteriaceae. Variation in the abundance of these genes was analysed as a function of the type of water, and possible correlations with cultivable bacteria, antimicrobial residue concentrations, and bacterial community composition and structure were analysed. HE was confirmed as an important source of bla(TEM) and vanA genes, and wastewater treatment showed a limited capacity to remove these resistance genes. The genes bla(TEM) and vanA presented the strongest correlations with culturable bacteria, antimicrobial residues and some bacterial populations, representing interesting candidates as indicator genes to monitor resistance in environmental samples. The intI1 gene was the most abundant in all samples, demonstrating that wastewater bacterial populations hold a high potential for gene acquisition.201427873693
7124180.9999Changes 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
3431190.9999Correlation between Bacterial Cell Density and Abundance of Antibiotic Resistance on Milking Machine Surfaces Assessed by Cultivation and Direct qPCR Methods. The relative abundance of antibiotic-resistant bacteria and antibiotic-resistance genes was surveyed for different parts of a milking machine. A cultivation approach based on swab samples showed a highly diverse microbiota, harboring resistances against cloxacillin, ampicillin, penicillin, and tetracycline. This approach demonstrated a substantial cloxacillin resistance of numerous taxa within milking machine microbiota coming along with regular use of cloxacillin for dry-off therapy of dairy cows. For the less abundant tetracycline-resistant bacteria we found a positive correlation between microbial cell density and relative abundance of tetracycline-resistant microorganisms (R(2) = 0.73). This indicated an accelerated dispersion of resistant cells for sampling locations with high cell density. However, the direct quantification of the tetM gene from the swap samples by qPCR showed the reverse relation to bacterial density if normalized against the abundance of 16S rRNA genes (R(2) = 0.88). The abundance of 16S rRNA genes was analyzed by qPCR combined with a propidium monoazide treatment, which eliminates 16S rRNA gene signals in negative controls.202337166501