Differential dose-response patterns of intracellular and extracellular antibiotic resistance genes under sub-lethal antibiotic exposure. - Related Documents




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750201.0000Differential dose-response patterns of intracellular and extracellular antibiotic resistance genes under sub-lethal antibiotic exposure. Although antibiotics are one of the most significant factors contributing to the propagation of antibiotic resistance genes (ARGs), studies on the dose-response relationship at sub-lethal concentrations of antibiotics remain scarce, despite their importance for assessing the risks of antibiotics in the environment. In this study, we constructed a series of microcosms to investigate the propagation of intracellular (iARGs) and extracellular (eARGs) ARGs in both water and biofilms when exposed to antibiotics at various concentrations (1-100 μg/L) and frequencies. Results showed that eARGs were more abundant than iARGs in water, while iARGs were the dominant ARGs form in biofilms. eARGs showed differentiated dose-response relationships from iARGs. The abundance of iARGs increased with the concentration of antibiotics as enhanced selective pressure overcame the metabolic burden of antibiotic-resistant bacteria carrying ARGs. However, the abundance of eARGs decreased with increasing antibiotic concentrations because less ARGs were secreted from bacterial hosts at higher concentrations (100 μg/L). Furthermore, combined exposure to two antibiotics (tetracycline & imipenem) showed a synergistic effect on the propagation of iARGs, but an antagonistic effect on the propagation of eARGs compared to exposure to a single antibiotic. When exposed to antibiotic at a fixed total dose, one-time dosing (1 time/10 d) favored the propagation of iARGs, while fractional dosing (5 times /10 d) favored the propagation of eARGs. This study sheds light on the propagation of antibiotic resistance in the environment and can help in assessing the risks associated with the use of antibiotics.202337257347
750110.9999Enhanced sensitivity of extracellular antibiotic resistance genes (ARGs) to environmental concentrations of antibiotic. As emerging contaminants, antibiotics are frequently present in various environments, particularly rivers, albeit often at sublethal concentrations (ng/L∼μg/L). Assessing the risk associated with these low levels, which are far below the lethal threshold for most organisms, remains challenging. In this study, using microcosms containing planktonic bacteria and biofilm, we examined how antibiotic resistance genes (ARGs) in different physical states, including intracellular ARGs (iARGs) and extracellular ARGs (eARGs) responded to these low-level antibiotics. Our findings reveal a positive correlation between sub-lethal antibiotic exposure (ranging from 0.1 to 10 μg/L) and increased prevalence (measured as ARG copies/16s rDNA) of both iARGs and eARGs in planktonic bacteria. Notably, eARGs demonstrated greater sensitivity to antibiotic exposure compared to iARGs, with a lower threshold (0.1 μg/L for eARGs versus 1 μg/L for iARGs) for abundance increase. Moreover, ARGs in biofilms demonstrates higher sensitivity to antibiotic exposure compared to planktonic bacteria. To elucidate the underlying mechanisms, we established an integrated population dynamics-pharmacokinetics-pharmacodynamics (PD-PP) model. This model indicates that the enhanced sensitivity of eARGs is primarily driven by an increased potential for plasmid release from cells under low antibiotic concentrations. Furthermore, the accumulation of antibiotic in biofilms induces a greater sensitivity of ARG compared to the planktonic bacteria. This study provides a fresh perspective on the development of antibiotic resistance and offers an innovative approach for assessing the risk of sublethal antibiotic in the environment.202438797215
763020.9998Coexistence of silver ion and tetracycline at environmentally relevant concentrations greatly enhanced antibiotic resistance gene development in activated sludge bioreactor. Antibiotic resistance has become a global public health problem. Recently, various environmental pollutants have been reported to induce the proliferation of antibiotic resistance. However, the impact of multiple pollutants (e.g., heavy metals and antibiotics), which more frequently occur in practical environments, is poorly understood. Herein, one widely distributed heavy metal (Ag(+)) and one frequently detected antibiotic (tetracycline) were chosen to investigate their coexisting effect on the proliferation of antibiotic resistance in the activated sludge system. Results show that the co-occurrence of Ag(+) and tetracycline at environmentally relevant concentrations exhibited no distinct inhibition in reactor performances. However, they inhibited the respiratory activity by 42%, destroyed the membrane structure by 218%, and increased membrane permeability by 29% compared with the blank control bioreactor. Moreover, the relative abundances of target antibiotic resistance genes (ARGs) (e.g., tetA, bla(TEM-1), and sulII) in effluent after exposure of coexisting Ag(+) and tetracycline were increased by 92-1983% compared with those in control reactor, which were 1.1-4.3 folds higher than the sum of the sole ones. These were possibly attributed to the enrichments of antibiotic-resistant bacteria. The results would illumine the coexisting effect of heavy metals and antibiotics on the dissemination of ARGs in activated sludge system.202234482077
751030.9998Impacts of antibiotics on biofilm bacterial community and disinfection performance on simulated drinking water supply pipe wall. Overuse of antibiotics is accelerating the spread of resistance risk in the environment. In drinking water supply systems, the effect of antibiotics on the resistance of biofilm is unclear, and there have been few studies in disinfectant-containing systems. Here, we designed a series of drinking water supply reactors to investigate the effects of antibiotics on biofilm and bacteria in the water. At low concentrations, antibiotics could promote the growth of bacteria in biofilm; among the tested antibiotics (tetracycline, sulfadiazine and chloramphenicol), tetracycline had the strongest ability to promote this. And the antibiotic resistant bacteria (ARB) could inhibit the growth of bacteria in drinking water. Results have shown that antibiotics enhanced the bacterial chlorine resistance in the effluent, but reduced that in the biofilm. Furthermore, metagenomic analysis showed that antibiotics reduced the richness of biofilm communities. The dominant phyla in the biofilm were Proteobacteria, Planctomycetes, and Firmicutes. In tetracycline-treated biofilm, the dominant phylum was Planctomycetes. In sulfadiazine- and chloramphenicol-treated groups, bacteria with complex cell structures preferentially accumulated. The dominant class in biofilm in the ARB-added group was Gammaproteobacteria. The abundance of antibiotic resistant genes (ARGs) was correlated with biofilm community structure. This study shows that antibiotics make the biofilm community structure of drinking water more resistant to chlorine. ARGs may be selective for certain bacteria in the process, and there may ultimately be enhanced chlorine and antibiotic resistance of effluent bacteria in drinking water.202134256291
750940.9998Assessing biofilm formation and resistance of vibrio parahaemolyticus on UV-aged microplastics in aquatic environments. UV degradation of marine microplastics (MPs) could increase their vector potential for pathogenic bacteria and threaten human health. However, little is known about how the degree of UV aging affects interactions between MPs and pathogens and how various types of MPs differ in their impact on seafood safety. This study investigated five types of UV-aged MPs and their impact on Vibrio parahaemolyticus, a seafood pathogen. MPs exposed to UV for 60 days showed similar physicochemical changes such as surface cracking and hydrophobicity reduction. Regardless of the type, longer UV exposure of MPs resulted in more biofilm formation on the surface under the same conditions. V. parahaemolyticus types that formed biofilms on the MP surface showed 1.4- to 5.0-fold upregulation of virulence-related genes compared to those that did not form biofilms, independently of UV exposure. However, longer UV exposure increased resistance of V. parahaemolyticus on MPs to chlorine, heat, and human gastrointestinal environment. This study implies that the more UV degradation occurs on MPs, the more microbial biofilm formation is induced, which can significantly increase virulence and environmental resistance of bacteria regardless of the type of MP.202438422694
808250.9998Deciphering the toxic effects of antibiotics on denitrification: Process performance, microbial community and antibiotic resistance genes. The extensive application of antibiotics, and the occurrence and spread of antibiotic resistance genes (ARGs) shade health risks to human and animal. The long-term effects of sulfamethoxazole (SMX) and tetracycline (TC) on denitrification process were evaluated in this study, with the focus on nitrogen removal performance, microbial community and ARGs. Results showed that low-concentration SMX and TC (<0.2 mg L(-1)) initially caused a deterioration in nitrogen removal performance, while higher concentrations (0.4-20 mg L(-1)) of both antibiotics had no further inhibitory influences. The abundances of ARGs in both systems generally increased during the whole period, and most of them had significant correlations with intI1, especially efflux-pump genes. Castellaniella, which was the dominant genus under antibiotic pressure, might be potential resistant bacteria. These findings provide an insight into the toxic effects of different antibiotics on denitrification process, and guides future efforts to control antibiotics pollution in ecosystems.202032250829
758160.9998Enhanced performance of anaerobic digestion of cephalosporin C fermentation residues by gamma irradiation-induced pretreatment. Antibiotic fermentation residues is a hazardous waste due to the existence of residual antibiotics and antibiotic resistance genes (ARGs), probably leading to the induction and spread of antibiotic resistant bacteria (ARB) in the environment, which could pose potential harm to the ecosystem and human health. It is urgent to develop an effective technology to remove the residual antibiotics and ARGs. In this study, the anaerobic digestion combined with gamma irradiation was applied for the disposal and utilization of cephalosporin C fermentation residues. The experimental results showed that the antibacterial activities of cephalosporin C against Staphylococcus aureus were significantly decreased after anaerobic digestion. The removal of tolC, a multidrug resistant gene, was improved up to 100% by the combination of gamma irradiation and anaerobic digestion compared to solely anaerobic digestion process, which may be due to the changes of microbial community structures induced by gamma irradiation.202031590081
796670.9998How heavy metal stress promotes dissemination of antibiotic resistance genes in the activated sludge process. Heavy metals have been recently revealed as promoters to antibiotic resistance gene (ARG) dissemination in water environment, but their influence on ARG transfer in the activated sludge process has not been clear. In this study, a set of sequencing batch reactors (SBRs) and micro-scale microfluidic chips were established to quantify the impacts of heavy metals (0.5 mM of Pb, 0.1 mM of As, and 0.005 mM of Hg) on the ARG spreading in the activated sludge consortium. Under heavy metal stress, transfer frequencies were 1.7-3.6 folds increase compared to the control. Gram-negative bacteria increased significantly after heavy metal added, which were more prone to receiving resistant plasmid from donors. Meanwhile, the relative expression of genes related to conjugation changed in activated sludge, especially the expression of outer membrane protein and oxidative stress regulatory genes increased by 2.9-7.4 folds and 7.8-13.1 folds, respectively. Furthermore, using microfluidic chips, the dynamics of ARG transfer was observed at single cell level under heavy metal pressure. Heavy metals firstly promoted conjugation and then vertical gene transfer played an important part for ARG spreading. The results provided in-depth understanding of the influence of heavy metals on ARG behavior in the environment.202235724617
750080.9998Dead but Not Forgotten: How Extracellular DNA, Moisture, and Space Modulate the Horizontal Transfer of Extracellular Antibiotic Resistance Genes in Soil. Antibiotic-resistant bacteria and the spread of antibiotic resistance genes (ARGs) pose a serious risk to human and veterinary health. While many studies focus on the movement of live antibiotic-resistant bacteria to the environment, it is unclear whether extracellular ARGs (eARGs) from dead cells can transfer to live bacteria to facilitate the evolution of antibiotic resistance in nature. Here, we use eARGs from dead, antibiotic-resistant Pseudomonas stutzeri cells to track the movement of eARGs to live P. stutzeri cells via natural transformation, a mechanism of horizontal gene transfer involving the genomic integration of eARGs. In sterile, antibiotic-free agricultural soil, we manipulated the eARG concentration, soil moisture, and proximity to eARGs. We found that transformation occurred in soils inoculated with just 0.25 μg of eDNA g(-1) soil, indicating that even low concentrations of soil eDNA can facilitate transformation (previous estimates suggested ∼2 to 40 μg eDNA g(-1) soil). When eDNA was increased to 5 μg g(-1) soil, there was a 5-fold increase in the number of antibiotic-resistant P. stutzeri cells. We found that eARGs were transformed under soil moistures typical of terrestrial systems (5 to 30% gravimetric water content) but inhibited at very high soil moistures (>30%). Overall, this work demonstrates that dead bacteria and their eARGs are an overlooked path to antibiotic resistance. More generally, the spread of eARGs in antibiotic-free soil suggests that transformation allows genetic variants to establish in the absence of antibiotic selection and that the soil environment plays a critical role in regulating transformation. IMPORTANCE Bacterial death can release eARGs into the environment. Agricultural soils can contain upwards of 10(9) ARGs g(-1) soil, which may facilitate the movement of eARGs from dead to live bacteria through a mechanism of horizontal gene transfer called natural transformation. Here, we track the spread of eARGs from dead, antibiotic-resistant Pseudomonas stutzeri cells to live antibiotic-susceptible P. stutzeri cells in sterile agricultural soil. Transformation increased with the abundance of eARGs and occurred in soils ranging from 5 to 40% gravimetric soil moisture but was lowest in wet soils (>30%). Transformants appeared in soil after 24 h and persisted for up to 15 days even when eDNA concentrations were only a fraction of those found in field soils. Overall, our results show that natural transformation allows eARGs to spread and persist in antibiotic-free soils and that the biological activity of eDNA after bacterial death makes environmental eARGs a public health concern.202235323025
757190.9998Ancient Oriental Wisdom still Works: Removing ARGs in Drinking Water by Boiling as compared to Chlorination. Antibiotic resistance genes (ARGs) in municipal drinking water may not be effectively removed during centralized treatment. To reduce potential health risks, water disinfection at the point-of-use scale is warranted. This study investigated the performance of boiling, a prevalent household water disinfection means, in response to ARGs contamination. We found that boiling was more efficient in inactivating both Escherichia coli and environmental bacteria compared to chlorination and pasteurization. Boiling of environmental bacteria suspension removed a much broader spectrum of ARGs and mobile genetic elements (up to 141 genes) than chlorination (up to 13 genes), such better performance was largely attributed to a stronger inactivation of chlorine-tolerant bacteria including Acinetobacter and Bacillus. Accumulation of extracellular ARGs was found during low-temperature heating (≤ 80°C) and in the initial stage of chlorination (first 3 min when initial chlorine was 5 mg/L and first 12 min when initial chlorine was 1 mg/L). These extracellular ARGs as well as the intracellular ARGs got removed as the heating temperature increased or the chlorination time prolonged. Under the same treatment time (30 min), high-temperature heating (≥ 90.1°C) damaged the DNA structure more thoroughly than chlorination (5 mg/L). Taking into account the low transferability of ARGs after DNA melting, boiling may provide an effective point-of-use approach to attenuating bacterial ARGs in drinking water and is still worth promoting in the future.202234910990
7565100.9998Microalgae Enhances the Adaptability of Epiphytic Bacteria to Sulfamethoxazole Stress and Proliferation of Antibiotic Resistance Genes Mediated by Integron. The transmission of ARGs in the microalgae-associated epiphytic bacteria remains unclear under antibiotic exposure, apart from altering the microbial community structure. In this study, Chlorella vulgaris cocultured with bacteria screened from surface water was examined to explore the spread of ARGs in the presence of sulfamethoxazole (SMX). The extracellular polymers released by Chlorella vulgaris could reduce antibiotic-induced collateral damage to bacteria, thus increasing the diversity of the microalgae-associated epiphytic bacteria. The abundances of sul1 and intI1 in the phycosphere at 1 mg/L SMX dose increased by 290 and 28 times, respectively. Metagenomic sequencing further confirmed that SMX bioaccumulation stimulated the horizontal transfer of sul1 mediated by intI1 in the microalgae-associated epiphytic bacteria, while reactive oxygen species (ROS)-mediated oxidative stress induced the SOS response and thus enhanced the transformation of sul1 in the J group. This is the first study to verify that microalgae protect bacteria from antibiotic damage and hinder the spread of ARGs mediated by SOS response, while the transfer of ARGs mediated by integron is promoted due to the bioaccumulation of SMX in the phycosphere. The results contribute to present comprehensive understanding of the risk of ARG proliferation by the presence of emerging contaminants residues in river.202439417646
8515110.9998In vitro assessment of the bacterial stress response and resistance evolution during multidrug-resistant bacterial invasion of the Xenopus tropicalis intestinal tract under typical stresses. The intestinal microbiome might be both a sink and source of resistance genes (RGs). To investigate the impact of environmental stress on the disturbance of exogenous multidrug-resistant bacteria (mARB) within the indigenous microbiome and proliferation of RGs, an intestinal conjugative system was established to simulate the invasion of mARB into the intestinal microbiota in vitro. Oxytetracycline (OTC) and heavy metals (Zn, Cu, Pb), commonly encountered in aquaculture, were selected as typical stresses for investigation. Adenosine 5'-triphosphate (ATP), hydroxyl radical (OH·(-)) and extracellular polymeric substance (EPS) were measured to investigate their influence on the acceptance of RGs by intestinal bacteria. The results showed that the transfer and diffusion of RGs under typical combined stressors were greater than those under a single stressor. Combined effect of OTC and heavy metals (Zn, Cu) significantly increased the activity and extracellular EPS content of bacteria in the intestinal conjugative system, increasing intI3 and RG abundance. OTC induced a notable inhibitory response in Citrobacter and exerted the proportion of Citrobacter and Carnobacterium in microbiota. The introduction of stressors stimulates the proliferation and dissemination of RGs within the intestinal environment. These results enhance our comprehension of the typical stresses effect on the RGs dispersal in the intestine.202438280323
7032120.9998Free Radicals on Aging Microplastics Regulated the Prevalence of Antibiotic Resistance Genes in the Aquatic Environment: New Insight into the Effect of Microplastics on the Spreading of Biofilm Resistomes. The spread of antibiotic resistance genes (ARGs) by microplastics has received a great concern in coexisting "hotspots". Despite most microplastics suffering from natural aging, little is known about the effect of aging microplastics (A-MPs) on ARGs dissemination. Here, we demonstrated significant suppression of A-MPs on ARGs dissemination in natural rivers. Although ARGs and mobile genetic elements (MGEs) were effectively enriched on A-MPs, the relative abundance of ARGs and MGEs on A-MPs as well as in receiving water decreased by approximately 21.4% to 42.3% during a period of 30 days of dissemination. Further investigation revealed that (•)OH was consistently generated on A-MPs with a maximum value of 0.2 μmol/g. Importantly, scavenging of (•)OH significantly increased the relative abundance of ARGs and MGEs both on A-MPs and in receiving water 1.4-29.1 times, indicating the vital role of (•)OH in suppressing ARGs dissemination. Microbial analysis revealed that (•)OH inhibited the potential antibiotic-resistant bacteria in surface biofilms, such as Pseudomonas and Acinetobacter (with a decrease of 68.8% and 89.3%). These results demonstrated that (•)OH was extensively produced on A-MPs, which greatly reduced both the vertical and horizontal gene transfer of ARGs. This study provided new insights into the dissemination of ARGs through microplastics in natural systems.202540359213
8517130.9998Influences of graphene on microbial community and antibiotic resistance genes in mouse gut as determined by high-throughput sequencing. Graphene is a promising candidate as an antibacterial material owning to its bacterial toxicity. However, little information on influence of graphene on gut microbiota is available. In this study, mice were exposed to graphene for 4 weeks, and high-throughput sequencing was applied to characterize the changes in microbial community and antibiotic resistance genes (ARGs) in mouse gut. The results showed that graphene exposure increased biodiversity of gut microbiota, and changed their community. The 1 μg/d graphene exposure had higher influences on the gut microbiota than 10 μg/d and 100 μg/d graphene exposures, which might be due to higher aggregation of high-level graphene. The influence of graphene on gut microbiota might attribute to that graphene could induce oxidative stress and damage of cell membrane integrity. The results were verified by the increase of ratio of Gram-negative bacteria. Outer membrane of Gram-negative bacteria could reduce the membrane damage induced by graphene and make them more tolerance to graphene. Further, we found that graphene exposure significantly increased the abundance and types of ARGs, indicating a potential health risk of graphene. This study firstly provides new insight to the health effects of graphene on gut microbiota.201626476051
7030140.9998Metagenomic profiling of antibiotic resistance genes/bacteria removal in urban water: Algal-bacterial consortium treatment system. Antibiotic resistance genes (ARGs) have exhibited significant ecological concerns, especially in the urban water that are closely associated with human health. In this study, with presence of exogenous Chlorella vulgaris-Bacillus licheniformis consortium, most of the typical ARGs and MGEs were removed. Furthermore, the relative abundance of potential ARGs hosts has generally decreased by 1-4 orders of magnitude, revealing the role of algal-bacterial consortium in cutting the spread of ARGs in urban water. While some of ARGs such as macB increased, which may be due to the negative impact of algicidal bacteria and algal viruses in urban water on exogenous C. vulgaris and the suppression of exogenous B. licheniformis by indigenous microorganisms. A new algal-bacterial interaction might form between C. vulgaris and indigenous microorganisms. The interplay between C. vulgaris and bacteria has a significant impact on the fate of ARGs removal in urban water.202438801952
7022150.9998Fate of antibiotics, antibiotic-resistant bacteria, and cell-free antibiotic-resistant genes in full-scale membrane bioreactor wastewater treatment plants. The removal of antibiotics, antibiotic-resistant bacteria (ARB), and cell-free antibiotic-resistant genes (ARGs) and the microbial community of ARB were investigated in detail to understand their fate and provide valuable information on the feasibility of full-scale membrane bioreactor (MBR). The potential risks of cell-free ARGs to the receiving environment were discovered. High influent antibiotic concentration could inhibit the microbial activity of MBR sludge, whereas good antibiotic removal could be maintained because of relatively long solid retention time and high biomass retention. Approximately 61.8%-77.5% of the total antibiotics were degraded, and 22.5%-38.2% of the total antibiotics were adsorbed by MBR sludge on average. The individual antibiotic removal presented intense discrepancy because of the chemical construction and distribution coefficient of antibiotics. Aeromonas exhibited specific antibiotic resistance to ampicillin and erythromycin, Escherichia became the predominant genera in kanamycin-ARB and tetracycline-ARB, and Klebsiella and Bacteroides were the particular genera that exhibited distinct antibiotic resistance to ciprofloxacin. A significant correlation was found between cell-free ARG abundance and ARB content, and relatively high effluent cell-free ARG abundance facilitated the proliferation and transmission of ARB. The impacts of the receiving environment to eliminate the ecological risks and severe threats to human health should be investigated because of the low decay ratio and long-term persistence of cell-free ARGs.202031986335
7979160.9998Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands. Constructed wetlands (CWs) have been identified as significant sources of micro(nano)plastics (MPs/NPs) and antibiotic resistance genes (ARGs) in aquatic environments. However, little is known about the impact of MPs/NPs exposure on horizontal gene transfer (HGT) of ARGs and shaping the corresponding ARG hosts' community. Herein, the contribution of polystyrene (PS) particles (control, 4 mm, 100 μm, and 100 nm) to ARG transfer was investigated by adding an engineered fluorescent Escherichia coli harboring RP4 plasmid-encoded ARGs into CWs. It was found MPs/NPs significantly promoted ARG transfer in a size-dependent manner in each CW medium (p < 0.05). The 100 μm-sized PS exhibited the most significant promotion of ARG transfer (p < 0.05), whereas 100 nm-sized PS induced limited promotion due to its inhibitory activity on microbes. The altered RP4-carrying bacterial communities suggested that MPs/NPs, especially 100 µm-PS, could recruit pathogenic and nitrifying bacteria to acquire ARGs. The increased sharing of RP4-carrying core bacteria in CW medium further suggested that ARGs can spread into CW microbiome using MPs/NPs as carriers. Overall, our results highlight the high risks of ARG dissemination induced by MPs/NPs exposure and emphasize the need for better control of plastic disposal to prevent the potential health threats.202337657315
7574170.9998Chlorine disinfection increases both intracellular and extracellular antibiotic resistance genes in a full-scale wastewater treatment plant. The emergence and spread of antibiotic resistance has posed a major threat to both human health and environmental ecosystem. Although the disinfection has been proved to be efficient to control the occurrence of pathogens, little effort is dedicated to revealing potential impacts of disinfection on transmission of antibiotic resistance genes (ARGs), particularly for free-living ARGs in final disinfected effluent of urban wastewater treatment plants (UWWTP). Here, we investigated the effects of chlorine disinfection on the occurrence and concentration of both extracellular ARGs (eARGs) and intracellular ARGs (iARGs) in a full-scale UWWTP over a year. We reported that the concentrations of both eARGs and iARGs would be increased by the disinfection with chlorine dioxide (ClO(2)). Specifically, chlorination preferentially increased the abundances of eARGs against macrolide (ermB), tetracycline (tetA, tetB and tetC), sulfonamide (sul1, sul2 and sul3), β-lactam (ampC), aminoglycosides (aph(2')-Id), rifampicin (katG) and vancomycin (vanA) up to 3.8 folds. Similarly, the abundances of iARGs were also increased up to 7.8 folds after chlorination. In terms of correlation analyses, the abundance of Escherichia coli before chlorination showed a strong positive correlation with the total eARG concentration, while lower temperature and higher ammonium concentration were assumed to be associated with the concentration of iARGs. This study suggests the chlorine disinfection could increase the abundances of both iARGs and eARGs, thereby posing risk of the dissemination of antibiotic resistance in environments.201829501757
6898180.9998Co-selection and stability of bacterial antibiotic resistance by arsenic pollution accidents in source water. Frequent heavy-metal pollution accidents severely deteriorated the source water quality of drinking water treatment plants (DWTP). Limited data have explicitly addressed the impact of these incidents on bacterial antibiotic resistance (BAR). In present study, we investigated the shift of antibiotic resistome caused by heavy metal pollution incidents via simulating an arsenic shock loading [As (III)], along with the associated risks imposed on drinking water systems. The results indicated that a quick co-selection of antibiotic resistant bacteria (ARB) was achieved after exposure to 0.2-1 mg/L As (III) for only 6 h, meanwhile, there was an increase of relative abundance of antibiotic resistance genes (ARGs) and mobile genetic elements. Most of the co-selected BAR could be maintained for at least 4 days in the absence of As (III) and antibiotics, implying that the pollution in source water possibly contributed to the preservation and proliferation of antibiotic resistance determinants in the subsequent DWTP. Bacterial community structure analysis showed a strong correlation between bacterial community shift and BAR promotion, and enrichment of opportunistic bacteria (e.g. Escherichia-Shigella, Empedobacter sp. and Elizabethkingia sp.). The results indicated a potential epidemiological threat to the public due to accident-level arsenic contamination in the source water. This study gave insight into understanding the source water pollution accidents from the perspective of bio-hazard and biological risks, and highlighted a neglected important source of BAR in drinking water systems.202031794937
7031190.9998Free-living lifestyle preferences drive the antibiotic resistance promotion during drinking water chlorination. The risk associated with antibiotic resistance genes (ARGs) in size-fractionated bacterial community during drinking water chlorination remains unclear, and is of paramount importance for risk mitigation through process selection and optimization. This study employed metagenomic approaches to reveal the alterations of ARGs, their potential functions and hosts within the free-living and particle-associated fractions. The total relative abundance of ARGs, mobile genetic elements (MGEs), and virulence factor genes (VFGs) significantly increased in the free-living fraction after chlorination. The contribution of the free-living fraction to the ARG relative abundance rose from 16.40 ± 1.31 % to 93.62 ± 0.47 % after chlorination. Multidrug resistance genes (e.g. mexF and mexW) were major contributors, and their co-occurrence with MGEs in the free-living fraction was enhanced after chlorination. Considering multiple perspectives, including presence, mobility, and pathogenicity, chlorination led to a significant risk of the antibiotic resistome in the free-living fraction. Moreover, potential functions of ARGs, such as cell wall/membrane/envelope biogenesis, defense mechanisms, and transcription in the free-living fraction, were intensified following chlorination. Potential pathogens, including Pseudomonas aeruginosa, Pseudomonas alcaligenes, and Acinetobacter junii, were identified as the predominant hosts of multidrug resistance genes, with their increased abundances primarily contributing to the rise of the corresponding ARGs. Overall, alterations of hosts as well as enhancing mobility and biological functions could collectively aid the proliferation and spread of ARGs in the free-living fraction after chlorination. This study provides novel insights into antibiotic resistance evolution in size-fractionated bacteria community and offers a management strategy for microbiological safety in drinking water.202438043346