Gamma Irradiation Influences the Survival and Regrowth of Antibiotic-Resistant Bacteria and Antibiotic-Resistance Genes on Romaine Lettuce. - Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
775901.0000Gamma Irradiation Influences the Survival and Regrowth of Antibiotic-Resistant Bacteria and Antibiotic-Resistance Genes on Romaine Lettuce. Contamination of romaine lettuce with human pathogens, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) occurs during production. Post-harvest interventions are emplaced to mitigate pathogens, but could also mitigate ARB and ARGs on vegetables. The objective of this research was to determine changes to lettuce phyllosphere microbiota, inoculated ARB, and the resistome (profile of ARGs) following washing with a sanitizer, gamma irradiation, and cold storage. To simulate potential sources of pre-harvest contamination, romaine lettuce leaves were inoculated with compost slurry containing antibiotic-resistant strains of pathogenic (Escherichia coli O157:H7) and representative of spoilage bacteria (Pseudomonas aeruginosa). Various combinations of washing with sodium hypochlorite (50 ppm free chlorine), packaging under modified atmosphere (98% nitrogen), irradiating (1.0 kGy) and storing at 4°C for 1 day versus 14 days were compared. Effects of post-harvest treatments on the resistome were profiled by shotgun metagenomic sequencing. Bacterial 16S rRNA gene amplicon sequencing was performed to determine changes to the phyllosphere microbiota. Survival and regrowth of inoculated ARB were evaluated by enumeration on selective media. Washing lettuce in water containing sanitizer was associated with reduced abundance of ARG classes that confer resistance to glycopeptides, β-lactams, phenicols, and sulfonamides (Wilcoxon, p < 0.05). Washing followed by irradiation resulted in a different resistome chiefly due to reductions in multidrug, triclosan, polymyxin, β-lactam, and quinolone ARG classes (Wilcoxon, p < 0.05). Irradiation followed by storage at 4°C for 14 days led to distinct changes to the β-diversity of the host bacteria of ARGs compared to 1 day after treatment (ANOSIM, R = 0.331; p = 0.003). Storage of washed and irradiated lettuce at 4°C for 14 days increased the relative abundance of Pseudomonadaceae and Carnobacteriaceae (Wilcoxon, p < 0.05), two groups whose presence correlated with detection of 10 ARG classes on the lettuce phyllosphere (p < 0.05). Irradiation resulted in a significant reduction (∼3.5 log CFU/g) of inoculated strains of E. coli O157:H7 and P. aeruginosa (ANOVA, p < 0.05). Results indicate that washing, irradiation and storage of modified atmosphere packaged lettuce at 4°C are effective strategies to reduce antibiotic-resistant E. coli O157:H7 and P. aeruginosa and relative abundance of various ARG classes.201931024491
718210.9997Effects 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
777120.9997Can chlorination co-select antibiotic-resistance genes? Selective pressures, such as chemical or heavy metal pollution, may co-select for bacterial antibiotic resistance in the environment. However, whether chlorination in water treatment can co-select antibiotic-resistant bacteria is controversial. In this study, high capacity quantitative polymerase chain reaction (qPCR) analysis was applied to target almost all known antibiotic-resistance genes (ARGs) (282 types) and 13 mobile genetic elements (MGEs) in bacteria detected in secondary effluents from a municipal wastewater treatment plant after chlorination. The results revealed that 125 unique ARGs were detected in non-chlorinated samples, and the number decreased (79-91 types) as the chlorine concentration was increased. Moreover, 7.49 × 10(4)-3.92 × 10(7) copies/100 ml water reduction of ARGs occurred with 4 mg Cl2/l. Considering the relative abundance of ARGs (i.e., ARG copies normalized to 16S rRNA gene copies), 119 ARGs decreased in response to chlorination, whereas only six ARGs, such as dfrA1, tetPB-03, tetPA, ampC-04, tetA-02, and erm(36), were potentially enriched by 10.90-, 10.06-, 8.63-, 6.86-, 3.77-, and 1.09-fold, respectively. Furthermore, the relative abundance of 12 detected MGEs was lower after chlorination. Therefore, chlorination was effective in reducing ARGs and MGEs rather than co-selecting them.201627192478
776030.9997From the Reclaimed Water Treatment Plant to Irrigation in Intensive Agriculture Farms: Assessment of the Fate of Antibiotics, Antibiotic Resistance Bacteria and Genes, and Microbial Pathogens at Real Scale. This work aims to investigate the occurrence of 31 antibiotics (ABs), 2 bacteria (Escherichia coli and Pseudomonas spp.) and their counterpart antibiotic-resistant bacteria (carbapenem and cephalosporin families), and several antibiotic-resistant genes (ARGs) throughout a full distribution system of reclaimed water (RW) in a real-scale scenario. The RW was analyzed (i) before and after the tertiary treatment (sand filtration and chlorination), (ii) during the storage period in secondary ponds before its use in irrigation, and (iii) directly in the droppers installed in four plastic-based greenhouses over 9 months. The results obtained in RW showed a bacterial concentration below the minimum required to reach class A (<10 CFU/100 mL, Regulation EU 2020/741), a reduction of the initial AB concentration (up to 13 ABs, total 4847 ± 1413 ng/L) of 58%, and no significant reduction of ARGs (Log units/100 mL: 16S rRNA (9.99 ± 0.80) > intI1 (8.80 ± 0.95) > bla(CTX-M32) (7.53 ± 0.63) > sul1 (7.08 ± 1.05) > bla(TEM) (6.81 ± 1.05) > qnrS (5.72 ± 0.82)). The storage of RW was a hotspot only for bacteria; an increase in all concentrations was observed in both main and secondary reservoirs, demonstrating that direct RW reuse is the most beneficial option to avoid significant bacterial regrowth. In all greenhouse droppers' systems, a significantly higher concentration of all bacteria was generally detected than in secondary reservoirs, demonstrating that this is another hotspot independent of whether the RW is used directly or not. Therefore, the RW storage and distribution may negatively affect the microbial water quality, while ABs and ARGs are detected along the entire scheme of urban wastewater reclamation and reuse, reaching the greenhouse environment (including soil and plants).202540923533
532340.9997Monitoring and assessing the impact of wastewater treatment on release of both antibiotic-resistant bacteria and their typical genes in a Chinese municipal wastewater treatment plant. Wastewater treatment plants (WWTPs) are important hotspots for the spread of antibiotic resistance. However, the release and impact factors of both antibiotic resistant bacteria and the relevant genes over long periods in WWTPs have rarely been investigated. In this study, the fate of bacteria and genes resistant to six commonly used antibiotics was assessed over a whole year. In WWTP effluent and biosolids, a high prevalence of heterotrophic bacteria resistant to vancomycin, cephalexin, sulfadiazine and erythromycin were detected, each with a proportion of over 30%. The corresponding genes (vanA, ampC, sulI and ereA) were all detected in proportions of (2.2 ± 0.8) × 10(-10), (6.2 ± 3.2) × 10(-9), (1.2 ± 0.8) × 10(-7) and (7.6 ± 4.8) × 10(-8), respectively, in the effluent. The sampling season imposed considerable influence on the release of all ARB. High release loads of most ARB were detected in the spring, while low release loads were generally found in the winter. In comparison, the ARG loads changed only slightly over various seasons. No statistical relevance was found between all ARB abundances and their corresponding genes over the long-term investigation period. This inconsistent behavior indicates that bacteria and genes should both be considered when exploring resistance characteristics in wastewater. A redundancy analysis was adopted to assess the impact of wastewater quality and operational conditions on antibiotic resistance. The results indicated that most ARB and ARG proportions were positively related to the COD and turbidity of the raw sewage, while negatively related to those of the effluent. DO and temperature exhibited strong negative relevance to most ARB prevalence.201424927359
718450.9997Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant. Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and genes (ARB and ARGs) in wastewaters. The present work aimed to build on the current knowledge about the effects of activated sludge and UV irradiation on antibiotic resistance determinants in biologically treated wastewaters. For that, the microbial community and ARGs' composition of samples collected after preliminary (APT), secondary (AST), and tertiary (ATT) treatments in a full-scale wastewater treatment plant using a modified activated sludge (MAS) system followed by an UV stage (16 mJ/cm(2)) were investigated through culture-dependent and independent approaches (including metagenomics). A total of 24 phyla and 460 genera were identified, with predominance of Gammaproteobacteria in all samples. Pathogenic genera corresponded to 8.6% of all sequences on average, mainly Acinetobacter and Streptococcus. Significant differences (p < 0.05) in the proportion of pathogens were observed between APT and the other samples, suggesting that the secondary treatment reduced its abundance. The MAS achieved 64.0-99.7% average removal efficiency for total (THB) and resistant heterotrophic bacteria, although the proportions of ARB/THB have increased for sulfamethoxazole, cephalexin, ciprofloxacin, and tetracycline. A total of 10(7) copies/mL of intI1 gene remained in the final effluent, suggesting that the treatment did not significantly remove this gene and possibly other ARGs. In accordance, metagenomic results suggested that number of reads recruited to plasmid-associated ARGs became more abundant in the pool throughout the treatment, suggesting that it affected more the bacteria without these ARGs than those with it. In conclusion, disinfected effluents are still a potential source for ARB and ARGs, which highlights the importance to investigate ways to mitigate their release into the environment.202235060061
722660.9997Seasonal variation in antibiotic resistance genes and bacterial phenotypes in swine wastewater during three-chamber anaerobic pond treatment. Antibiotic resistance is a global public health concern. Antibiotic usage in pigs makes swine wastewater (SW) a reservoir for antibiotic resistance genes (ARGs). SW is usually stored and treated in a three-chamber anaerobic pond (3-CAP) in medium and small pig farms in northern China. However, the yet unexplored presence of ARGs in SW during 3-CAP treatment may result in ARGs spreading into the environment if farmers apply SW to farmland as a liquid organic fertilizer. This study investigated the profiles of and changes in ARGs in SW during its treatment in 3-CAP over four seasons and analyzed the correlation between ARGs and bacterial phenotypes, along with the physicochemical parameters of the water. The results revealed that ARG abundance decreased considerably after 3-CAP treatment in April (47%), October (47%), and December (62%) but increased in May (43%) and August (73%). The ARG copies in the influent and other SW samples increased significantly from 10(7) copies/mL in April to 10(9) copies/mL in October and were maintained in December. The increase in ARG abundance was not as rapid as the growth of the bacterial population, resulting in lower relative abundance in October and December. Bacterial communities possessed more sul1 and tetM genes, which were also positively correlated with mobile genetic elements. After the 3-CAP treatment, 16% of antibiotics and 60% of heavy metals were removed, and both had a weak correlation with ARGs. Predicted phenotypes showed that gram-positive (G(+)) and gram-negative (G(-)) bacteria have different capacities for carrying ARGs. G(+) bacteria carry more ARGs than G(-) bacteria. This study revealed the persistence of ARGs in SW after 3-CAP treatment over different seasons. Applying SW in the proper month will mitigate ARG dissemination to the environment.202336208778
351170.9996Antibiotics and their associations with antibiotic resistance genes and microbial communities in estuarine and coastal sediment of Quanzhou Bay, Southeast China. The antibiotic concentrations spanned from 11.2 to 173.8 ng/g, with quinolones and tetracyclines being observed to be prevalent. The amount of microbial biomass as determined by Phospholipid fatty acid (PLFA) ranged from 2.92 to 10.99 mg kg(-1), with G- bacteria dominating. A total of 254 distinct ARGs and 10 MEGs were identified, with multidrug ARGs having the highest relative abundance (1.18 × 10(-2) to 3.00 × 10(-1) copies/16S rRNA gene copies), while vancomycin and sulfonamide resistance genes were the least abundant. Results from canonical-correlation analyses combined with redundancy analysis indicated that macrolides were significantly related to the shifts of microbial community structure in sediments, particularly in G+ bacteria that were more sensitive to antibiotic residues. It was observed that sulfonamide ARGs had a greater correlation with residual antibiotics than other ARGs. This study provided a field evidence that multiple residual antibiotics from coastal sites could cause fundamental shifts in microbial community and their associated ARGs.202337714074
776380.9996Antibiotic resistance genes fate and removal by a technological treatment solution for water reuse in agriculture. In order to mitigate the potential effects on the human health which are associated to the use of treated wastewater in agriculture, antibiotic resistance genes (ARGs) are required to be carefully monitored in wastewater reuse processes and their spread should be prevented by the development of efficient treatment technologies. Objective of this study was the assessment of ARGs reduction efficiencies of a novel technological treatment solution for agricultural reuse of municipal wastewaters. The proposed solution comprises an advanced biological treatment (Sequencing Batch Biofilter Granular Reactor, SBBGR), analysed both al laboratory and pilot scale, followed by sand filtration and two different disinfection final stages: ultraviolet light (UV) radiation and peracetic acid (PAA) treatments. By Polymerase Chain Reaction (PCR), the presence of 9 ARGs (ampC, mecA, ermB, sul1, sul2, tetA, tetO, tetW, vanA) were analysed and by quantitative PCR (qPCR) their removal was determined. The obtained results were compared to the reduction of total bacteria (16S rDNA gene) and of a faecal contamination indicator (Escherichia coli uidA gene). Only four of the analysed genes (ermB, sul1, sul2, tetA) were detected in raw wastewater and their abundance was estimated to be 3.4±0.7 x10(4) - 9.6±0.5 x10(9) and 1.0±0.3 x10(3) to 3.0±0.1 x10(7) gene copies/mL in raw and treated wastewaters, respectively. The results show that SBBGR technology is promising for the reduction of ARGs, achieving stable removal performance ranging from 1.0±0.4 to 2.8±0.7 log units, which is comparable to or higher than that reported for conventional activated sludge treatments. No reduction of the ARGs amount normalized to the total bacteria content (16S rDNA), was instead obtained, indicating that these genes are removed together with total bacteria and not specifically eliminated. Enhanced ARGs removal was obtained by sand filtration, while no reduction was achieved by both UV and PAA disinfection treatments tested in our study.201627450254
776790.9996Degradation of plasmid-mediated resistance genes in poultry slaughterhouse wastewater employing a UV/H(2)O(2) process: A metagenomic approach. Poultry slaughterhouse effluents are important hotspots for the spread of both antibiotic-resistant bacteria (ARBs) and antibiotic resistance genes (ARGs), contributing to the antimicrobial resistance (AMR). This study reports a novel investigation to assess the effects of UV/H(2)O(2) treatment on the removal of metaplasmidome-mediated ARGs from poultry slaughterhouse effluents. The effluent samples were subjected at 0.005-0.15 mol L(-1) of H(2)O(2) and pH conditions (3, 5, 7 and 9). Bacterial community (rrs 16S rRNA), Escherichia coli (uidA) antimicrobial resistance (sul1 and int1) and metagenomic plasmid DNA removal were assessed. The UV/H(2)O(2) treatment employing H(2)O(2) = 0.01 mol L(-1) at pH 3 resulted in decreased of several markers (uidA, sul1 and int1). A metaplasmidome indicated the persistence of Burkholderiales order. The UV/H(2)O(2) process reduced plasmid-associated ARGs by 92.5% and 90.4% at pH 3 and 7, respectively. Persistent genes were mainly composed of genes associated with efflux pumps and resistance to beta-lactams and fluoroquinolones. These findings contribute to mitigate the spread of AMR in the agricultural sector, especially through the implementation of more efficient treatments, and reducing the use of antibiotics in livestock farming.202539826254
5324100.9996Abundances of tetracycline, sulphonamide and beta-lactam antibiotic resistance genes in conventional wastewater treatment plants (WWTPs) with different waste load. Antibiotics and antibiotic resistant bacteria enter wastewater treatment plants (WWTPs), an environment where resistance genes can potentially spread and exchange between microbes. Several antibiotic resistance genes (ARGs) were quantified using qPCR in three WWTPs of decreasing capacity located in Helsinki, Tallinn, and Tartu, respectively: sulphonamide resistance genes (sul1 and sul2), tetracycline resistance genes (tetM and tetC), and resistance genes for extended spectrum beta-lactams (blaoxa-58, blashv-34, and blactx-m-32). To avoid inconsistencies among qPCR assays we normalised the ARG abundances with 16S rRNA gene abundances while assessing if the respective genes increased or decreased during treatment. ARGs were detected in most samples; sul1, sul2, and tetM were detected in all samples. Statistically significant differences (adjusted p<0.01) between the inflow and effluent were detected in only four cases. Effluent values for blaoxa-58 and tetC decreased in the two larger plants while tetM decreased in the medium-sized plant. Only blashv-34 increased in the effluent from the medium-sized plant. In all other cases the purification process caused no significant change in the relative abundance of resistance genes, while the raw abundances fell by several orders of magnitude. Standard water quality variables (biological oxygen demand, total phosphorus and nitrogen, etc.) were weakly related or unrelated to the relative abundance of resistance genes. Based on our results we conclude that there is neither considerable enrichment nor purification of antibiotic resistance genes in studied conventional WWTPs.201425084517
7237110.9996Dominant denitrifying bacteria are important hosts of antibiotic resistance genes in pig farm anoxic-oxic wastewater treatment processes. The anoxic-oxic (A/O) wastewater treatment process that is widely used in pig farms in China is an important repository for antibiotic resistance genes (ARGs). However, the distribution of ARGs and their hosts in the A/O process has not been well characterized. In this study, the wastewaters in the anoxic and oxic tanks for A/O processes were collected from 38 pig farms. The concentrations of 20 subtypes of ARGs, 5 denitrification-related genes, 2 integrons, and bacterial community composition were investigated. Bacterial genome binning was performed using metagenome sequencing. In this study, 20 subtypes of ARGs and integrons were detected in all sampling sites. A total of 16 of the 20 subtypes of ARGs were detected with the highest abundance in anoxic tanks, and sul1 was detected with a maximum average abundance of 19.21 ± 0.24 log(10) (copies/mL). Cooccurrence patterns were observed for some genes in the pig farm A/O process, such as sul1 and intl1, sul1 and tetG, and tetO and tetW. There was a significant cooccurrence pattern between the dominant denitrifying bacteria and some ARGs (bla(TEM), ermB, tetC, tetH and tetQ), so the dominant denitrifying bacteria were considered to be potential ARG hosts. In addition, 170 highly abundant bacterial genome bins were assembled and further confirmed that the denitrifying bacteria Brachymonas, Candidatus Competibacter, Thiobacillus and Steroidobacter were the important ARG hosts in the pig farm A/O process, providing a useful reference for the surveillance and risk management of ARGs in pig farm wastewater.202032615347
7768120.9996Drinking water biofiltration: Behaviour of antibiotic resistance genes and the association with bacterial community. Antibiotic resistance genes (ARGs) are being detected in drinking water frequently, constituting a major public health issue. As a typical drinking water treatment process, the biofilter may harbour various ARGs due to the filter biofilms established during the filtration process. The objective of this study was to investigate the behaviour of ARGs (bla(CTX-M), bla(OXA-1), bla(TEM), ermB, tetA, tetG, tetQ, tetW, tetX, sul 1, sul 2, dfrA1 and dfrA12) and their possible association with bacteria in a bench-scale biofiltration system. The impact of filter media on horizontal gene transfer (HGT) was also explored using a model conjugative plasmid, RP1. The biofiltration system comprised four types of biofilters, including sand, granular activated carbon (GAC), GAC sandwich, and anthracite-sand biofilters. Results showed that although the absolute abundance of ARGs decreased (0.97-log reduction on average), the ARGs' abundance normalised to bacterial numbers showed an increasing trend in the filtered water. Biofilms collected from the surface layer revealed the lowest relative abundance of ARGs (p < 0.01) compared to the deeper layer biofilms, indicating that the proportion of ARG-carrying bacteria was greater in the lower position. Most chosen ARG numbers correlated to Proteobacteria, Acidobacteria and Nitrospirae phyla, which accounted for 51.9%, 5.2% and 2.0% of the biofilm communities, respectively. GAC media revealed the highest transfer frequency (2.60 × 10(-5)), followed by anthracite (5.31 × 10(-6)) and sand (2.47 × 10(-6)). Backwashing can reduce the transferability of RP1 plasmid significantly in biofilms but introduces more transconjugants into the planktonic phase. Overall, the results of this study could enhance our understanding of the prevalence of ARGs in drinking water biofiltration treatment.202032650149
5358130.9996Abundance of antibiotics, antibiotic resistance genes and bacterial community composition in wastewater effluents from different Romanian hospitals. Antimicrobial resistance represents a growing and significant public health threat, which requires a global response to develop effective strategies and mitigate the emergence and spread of this phenomenon in clinical and environmental settings. We investigated, therefore, the occurrence and abundance of several antibiotics and antibiotic resistance genes (ARGs), as well as bacterial community composition in wastewater effluents from different hospitals located in the Cluj County, Romania. Antibiotic concentrations ranged between 3.67 and 53.05 μg L(-1), and the most abundant antibiotic classes were β-lactams, glycopeptides, and trimethoprim. Among the ARGs detected, 14 genes confer resistance to β-lactams, aminoglycosides, chloramphenicol, macrolide-lincosamide-streptogramin B (MLSB) antibiotics, sulfonamides, and tetracyclines. Genes encoding quaternary ammonium resistance and a transposon-related element were also detected. The sulI and qacEΔ1 genes, which confer resistance to sulfonamides and quaternary ammonium, had the highest relative abundance with values ranging from 5.33 × 10(-2) to 1.94 × 10(-1) and 1.94 × 10(-2) to 4.89 × 10(-2) copies/16 rRNA gene copies, respectively. The dominant phyla detected in the hospital wastewater samples were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. Among selected hospitals, one of them applied an activated sludge and chlorine disinfection process before releasing the effluent to the municipal collector. This conventional wastewater treatment showed moderate removal efficiency of the studied pollutants, with a 55-81% decrease in antibiotic concentrations, 1-3 order of magnitude lower relative abundance of ARGs, but with a slight increase of some potentially pathogenic bacteria. Given this, hospital wastewaters (raw or treated) may contribute to the spread of these emerging pollutants in the receiving environments. To the best of our knowledge, this study quantified for the first time the abundance of antibiotics and ARGs in wastewater effluents from different Romanian hospitals.201728347610
7212140.9996Simulated Winter Incubation of Soil With Swine Manure Differentially Affects Multiple Antimicrobial Resistance Elements. Gastrointestinal bacteria that harbor antibiotic resistance genes (ARG) become enriched with antibiotic use. Livestock manure application to cropland for soil fertility presents a concern that ARG and bacteria may proliferate and be transported in the environment. In the United States, manure applications typically occur during autumn with slow mineralization until spring planting season. A laboratory soil incubation study was conducted mimicking autumn swine manure application to soils with concentrations of selected ARG monitored during simulated 120-day winter incubation with multiple freeze-thaw events. Additionally, the effects of two soil moistures [10 and 30% water holding capacity (WHC)] and two manure treatments [raw versus hydrated lime alkaline stabilization (HLAS)] were assessed. Fourteen tetracycline resistance genes were evaluated; tet(D), tet(G), and tet(L) were detected in background soil while swine manure contained tet(A), tet(B), tet(C), tet(G), tet(M), tet(O), tet(Q), and tet(X). By day 120, the manure-borne tet(M) and tet(O) were still detected while tet(C), tet(D), tet(L), and tet(X) genes were detected less frequently. Other tet resistance genes were detected rarely, if at all. The sum of unique tet resistance genes among all treatments decreased during the incubation from an average of 8.9 to 3.8 unique tet resistance genes. Four resistance elements, intI1, bla (ctx-m-32), sul(I), erm(B), and 16s rRNA genes were measured using quantitative PCR. ARG abundances relative to 16S abundance were initially greater in the raw manure compared to background soil (-1.53 to -3.92 log abundance in manure; -4.02 to <-6.7 log abundance in soil). In the mixed manure/soil, relative abundance of the four resistance elements decreased (0.87 to 1.94 log abundance) during the incubation largely because 16S rRNA genes increased by 1.21 log abundance. Throughout the incubation, the abundance of intI1, bla (ctx-m-32), sul(I), and erm(B) per gram in soil amended with HLAS-treated manure was lower than in soil amended with raw manure. Under low initial soil moisture conditions, HLAS treatment reduced the abundance of intI1 and resulted in loss of bla (ctx-m-32), sul(I), and erm(B)] compared to other treatment-moisture combinations. Although one might expect antibiotic resistance to be relatively unchanged after simulated winter manure application to soil, a variety of changes in diversity and relative abundance can be expected.202033391241
7179150.9996Prevalence and proliferation of antibiotic resistance genes in two municipal wastewater treatment plants. The propagation of antibiotic resistance genes (ARGs) is an emerging health concern worldwide. Thus, it is important to understand and mitigate their occurrence in different systems. In this study, 30 ARGs that confer resistance to tetracyclines, sulfonamides, quinolones or macrolides were detected in two activated sludge wastewater treatment plants (WWTPs) in northern China. Bacteria harboring ARGs persisted through all treatment units, and survived disinfection by chlorination in greater percentages than total Bacteria (assessed by 16S rRNA genes). Although the absolute abundances of ARGs were reduced from the raw influent to the effluent by 89.0%-99.8%, considerable ARG levels [(1.0 ± 0.2) × 10(3) to (9.5 ± 1.8) × 10(5) copies/mL)] were found in WWTP effluent samples. ARGs were concentrated in the waste sludge (through settling of bacteria and sludge dewatering) at (1.5 ± 2.3) × 10(9) to (2.2 ± 2.8) × 10(11) copies/g dry weight. Twelve ARGs (tetA, tetB, tetE, tetG, tetH, tetS, tetT, tetX, sul1, sul2, qnrB, ermC) were discharged through the dewatered sludge and plant effluent at higher rates than influent values, indicating overall proliferation of resistant bacteria. Significant antibiotic concentrations (2%-50% of raw influent concentrations) remained throughout all treatment units. This apparently contributed selective pressure for ARG replication since the relative abundance of resistant bacteria (assessed by ARG/16S rRNA gene ratios) was significantly correlated to the corresponding effluent antibiotic concentrations. Similarly, the concentrations of various heavy metals (which induce a similar bacterial resistance mechanism as antibiotics - efflux pumps) were also correlated to the enrichment of some ARGs. Thus, curtailing the release of antibiotics and heavy metals to sewage systems (or enhancing their removal in pre-treatment units) may alleviate their selective pressure and mitigate ARG proliferation in WWTPs.201526372743
7225160.9996Risk assessment of the spread of antibiotic resistance genes from hospitals to the receiving environment via wastewater treatment plants. Antibiotics and antibiotic resistance genes (ARGs) enter the receiving environment from hospitals through wastewater treatment plants (WWTPs), increasing the presence of exogenous ARGs and conditional pathogens in the receiving environment, thereby elevating the risk of drug resistance. This study, based on metagenomics, investigated changes in risk across each node in the ARG transmission chain, from hospitals through WWTPs to downstream receiving water and sediments. The results showed that the total concentration of antibiotics decreased from 1467.80 ± 215.30 µg/L in hospital wastewater to 111.52 ± 18.70 µg/L in downstream receiving water, achieving a 92.40 % removal rate. However, the types of high ecological risk antibiotics in hospital wastewater were only reduced by 38.46 % after treatment by hospitals and sewage treatment plants. The abundance of Rank I ARGs was reduced by 37.03 % in hospital sewage treatment stations and 28.57 % in WWTPs, but these ARGs accounted for 81.8 % of the Rank I ARGs in receiving water. The potential host bacteria for these ARGs were mainly Proteobacteria, which carried bacitracin and multidrug resistance genes. While WWTPs removed 66.67 % of the conditional pathogens, bacteria such as Acinetobacter and Streptococcus still entered the receiving water. MetaCompare revealed that the potential transmission risk of ARGs decreased by 24.31 % after hospital wastewater treatment and by 20.71 % after WWTPs, with the risk of the receiving water being 7.01 times that in sediments. The potential risk assessment framework developed in this study for antibiotics and ARGs in the environment provides a theoretical guidance for antibiotic treatment and ARGs environmental risk control.202541161238
5303170.9996Wastewater irrigation increases the abundance of potentially harmful gammaproteobacteria in soils in Mezquital Valley, Mexico. Wastewater contains large amounts of pharmaceuticals, pathogens, and antimicrobial resistance determinants. Only a little is known about the dissemination of resistance determinants and changes in soil microbial communities affected by wastewater irrigation. Community DNAs from Mezquital Valley soils under irrigation with untreated wastewater for 0 to 100 years were analyzed by quantitative real-time PCR for the presence of sul genes, encoding resistance to sulfonamides. Amplicon sequencing of bacterial 16S rRNA genes from community DNAs from soils irrigated for 0, 8, 10, 85, and 100 years was performed and revealed a 14% increase of the relative abundance of Proteobacteria in rainy season soils and a 26.7% increase in dry season soils for soils irrigated for 100 years with wastewater. In particular, Gammaproteobacteria, including potential pathogens, such as Pseudomonas, Stenotrophomonas, and Acinetobacter spp., were found in wastewater-irrigated fields. 16S rRNA gene sequencing of 96 isolates from soils irrigated with wastewater for 100 years (48 from dry and 48 from rainy season soils) revealed that 46% were affiliated with the Gammaproteobacteria (mainly potentially pathogenic Stenotrophomonas strains) and 50% with the Bacilli, whereas all 96 isolates from rain-fed soils (48 from dry and 48 from rainy season soils) were affiliated with the Bacilli. Up to six types of antibiotic resistance were found in isolates from wastewater-irrigated soils; sulfamethoxazole resistance was the most abundant (33.3% of the isolates), followed by oxacillin resistance (21.9% of the isolates). In summary, we detected an increase of potentially harmful bacteria and a larger incidence of resistance determinants in wastewater-irrigated soils, which might result in health risks for farm workers and consumers of wastewater-irrigated crops.201424951788
3214180.9996Characteristics of the antibiotic resistance genes in the soil of medical waste disposal sites. The inappropriate disposal of medical waste allows bacteria to acquire antibiotic resistance, which results in a threat to public health. Antibiotic resistance gene (ARG) profiles were determined for 45 different soil samples containing medical waste and 15 nearby soil samples as controls. Besides physical and chemical analyses (i.e., dry matter content, pH value, and metal content), the genomes of microorganisms from the soil samples were extracted for high-throughput sequencing. ARG abundances of these samples were obtained by searching the metagenomic sequences against the antibiotic resistance gene database and the copies of ARGs per copy of the 16S rRNA gene at different levels were assessed. The results showed medical waste accumulation significantly enriched the contents of Cu, Cr, Pb, and As in the tested soil samples. Compared to the controls, the samples collected from areas containing medical waste were significantly enriched (p < 0.05, t-test) with ARGs annotated as sulfonamide and multidrug resistance genes, and in particular, the subtypes sul1 and sul2 (sulfonamide resistance genes), and multidrug_transporter (multidrug resistance gene). Moreover, the ARGs of the samples from the polluted areas were more diverse than those of the control samples (p < 0.05, t-test). The comparatively higher abundance and diversity of ARGs in contaminated soil pose a potential risk to human health.202032402966
7764190.9996Air-drying beds reduce the quantities of antibiotic resistance genes and class 1 integrons in residual municipal wastewater solids. This study investigated whether air-drying beds reduce antibiotic resistance gene (ARG) concentrations in residual municipal wastewater solids. Three laboratory-scale drying beds were operated for a period of nearly 100 days. Real-time PCR was used to quantify 16S rRNA genes, 16S rRNA genes specific to fecal bacteria (AllBac) and human fecal bacteria (HF183), the integrase gene of class 1 integrons (intI1), and five ARGs representing a cross-section of antibiotic classes and resistance mechanisms (erm(B), sul1, tet(A), tet(W), and tet(X)). Air-drying beds were capable of reducing all gene target concentrations by 1 to 5 orders of magnitude, and the nature of this reduction was consistent with both a net decrease in the number of bacterial cells and a lack of selection within the microbial community. Half-lives varied between 1.5 d (HF183) and 5.4 d (tet(X)) during the first 20 d of treatment. After the first 20 d of treatment, however, half-lives varied between 8.6 d (tet(X)) and 19.3 d (AllBac), and 16S rRNA gene, intI1, and sul1 concentrations did not change (P > 0.05). These results demonstrate that air-drying beds can reduce ARG and intI1 concentrations in residual municipal wastewater solids within timeframes typical of operating practices.201323909386