# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 3845 | 0 | 1.0000 | A novel microfluidic system enables visualization and analysis of antibiotic resistance gene transfer to activated sludge bacteria in biofilm. Antibiotic resistance genes (ARGs) in environment have become a growing public concern, due to their potential to be obtained by pathogens and their duplication along cell division. Horizontal gene transfer (HGT) was reported to be responsible for ARGs dissemination in microbes, but the HGT feature in environmental biofilm was still unclear due to insufficient assay tools. To address this challenge, we applied a novel microfluidic system to cultivate thin biofilm by continuous supply of nutrients and close contact between cells. Resembling the living state of biofilm in open environment, this chip visualized the transfer of ARG-encoded plasmids RP4 and pKJK5 to the receptors, e.g., activated sludge bacteria. The average plasmid transfer frequency per receptor (T/R) from RP4-hosted Pseudomonas putida KT2440 to activated sludge bacteria was quantified to be 2.5 × 10(-3) via flow cytometry, and T/R for pKJK5-hosted Escherichia coli MG1655 was 8.9 × 10(-3), while the corresponding average frequencies per donor (T/D) were diverse for the two host strains as 4.3 × 10(-3) and 1.4 × 10(-1) respectively. The difference between T/R and T/D was explained by the plasmid transfer kinetics, implying specific purposes of the two calculations. Finally, we collected the transconjugants by fluorescent activated cell sorting and further sequenced their 16S rDNA. Bacteria from phyla Proteobacteria and Firmicutes were found more susceptible to be transconjugants than those from Bacteroidetes. Our work demonstrated that microfluidic system was advantageous in biofilm HGT study, which can provide more insights into environmental ARG control. | 2018 | 29909325 |
| 3844 | 1 | 0.9999 | Effects 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. | 2022 | 36094214 |
| 7529 | 2 | 0.9999 | Fate of Antibiotic Resistant Pseudomonas putida and Broad Host Range Plasmid in Natural Soil Microcosms. Plasmid conjugation is one of the dominant mechanisms of horizontal gene transfer, playing a noticeable role in the rapid spread of antibiotic resistance genes (ARGs). Broad host range plasmids are known to transfer to diverse bacteria in extracted soil bacterial communities when evaluated by filter mating incubation. However, the persistence and dissemination of broad range plasmid in natural soil has not been well studied. In this study, Pseudomonas putida with a conjugative antibiotic resistance plasmid RP4 was inoculated into a soil microcosm, the fate and persistence of P. putida and RP4 were monitored by quantitative PCR. The concentrations of P. putida and RP4 both rapidly decreased within 15-day incubation. P. putida then decayed at a significantly lower rate during subsequent incubation, however, no further decay of RP4 was observed, resulting in an elevated RP4/P. putida ratio (up to 10) after 75-day incubation, which implied potential transfer of RP4 to soil microbiota. We further sorted RP4 recipient bacteria from the soil microcosms by fluorescence-activated cell sorting. Spread of RP4 increased during 75-day microcosm operation and was estimated at around 10(-4) transconjugants per recipient at the end of incubation. Analysis of 16S rRNA gene sequences of transconjugants showed that host bacteria of RP4 were affiliated to more than 15 phyla, with increased diversity and shift in the composition of host bacteria. Proteobacteria was the most dominant phylum in the transconjugant pools. Transient transfer of RP4 to some host bacteria was observed. These results emphasize the prolonged persistence of P. putida and RP4 in natural soil microcosms, and highlight the potential risks of increased spread potential of plasmid and broader range of host bacteria in disseminating ARGs in soil. | 2019 | 30881351 |
| 7399 | 3 | 0.9999 | Aquatic animals promote antibiotic resistance gene dissemination in water via conjugation: Role of different regions within the zebra fish intestinal tract, and impact on fish intestinal microbiota. The aqueous environment is one of many reservoirs of antibiotic resistance genes (ARGs). Fish, as important aquatic animals which possess ideal intestinal niches for bacteria to grow and multiply, may ingest antibiotic resistance bacteria from aqueous environment. The fish gut would be a suitable environment for conjugal gene transfer including those encoding antibiotic resistance. However, little is known in relation to the impact of ingested ARGs or antibiotic resistance bacteria (ARB) on gut microbiota. Here, we applied the cultivation method, qPCR, nuclear molecular genetic marker and 16S rDNA amplicon sequencing technologies to develop a plasmid-mediated ARG transfer model of zebrafish. Furthermore, we aimed to investigate the dissemination of ARGs in microbial communities of zebrafish guts after donors carrying self-transferring plasmids that encode ARGs were introduced in aquaria. On average, 15% of faecal bacteria obtained ARGs through RP4-mediated conjugal transfer. The hindgut was the most important intestinal region supporting ARG dissemination, with concentrations of donor and transconjugant cells almost 25 times higher than those of other intestinal segments. Furthermore, in the hindgut where conjugal transfer occurred most actively, there was remarkable upregulation of the mRNA expression of the RP4 plasmid regulatory genes, trbBp and trfAp. Exogenous bacteria seem to alter bacterial communities by increasing Escherichia and Bacteroides species, while decreasing Aeromonas compared with control groups. We identified the composition of transconjugants and abundance of both cultivable and uncultivable bacteria (the latter accounted for 90.4%-97.2% of total transconjugants). Our study suggests that aquatic animal guts contribute to the spread of ARGs in water environments. | 2017 | 28742284 |
| 3848 | 4 | 0.9998 | Effect of environmental factors on conjugative transfer of antibiotic resistance genes in aquatic settings. Antimicrobial-resistance genes (ARGs) are spread among bacteria by horizontal gene transfer, however, the effect of environmental factors on the dynamics of the ARG in water environments has not been very well understood. In this systematic review, we employed the regression tree algorithm to identify the environmental factors that facilitate/inhibit the transfer of ARGs via conjugation in planktonic/biofilm-formed bacterial cells based on the results of past relevant research. Escherichia coli strains were the most studied genus for conjugation experiments as donor/recipient in the intra-genera category. Conversely, Pseudomonas spp., Acinetobacter spp., and Salmonella spp. were studied primarily as recipients across inter-genera bacteria. The conjugation efficiency (ce) was found to be highly dependent on the incubation period. Some antibiotics, such as nitrofurantoin (at ≥0.2 µg ml-1) and kanamycin (at ≥9.5 mg l-1) as well as metallic compounds like mercury (II) chloride (HgCl2, ≥3 µmol l-1), and vanadium (III) chloride (VCl3, ≥50 µmol l-1) had enhancing effect on conjugation. The highest ce value (-0.90 log10) was achieved at 15°C-19°C, with linoleic acid concentrations <8 mg l-1, a recognized conjugation inhibitor. Identifying critical environmental factors affecting ARG dissemination in aquatic environments will accelerate strategies to control their proliferation and combat antibiotic resistance. | 2024 | 38830804 |
| 7965 | 5 | 0.9998 | Screening and evaluation of heavy metals facilitating antibiotic resistance gene transfer in a sludge bacterial community. Recent growing evidence suggests that heavy metals can stimulate the transfer of antibiotic resistance genes (ARGs) between bacteria. However, most previous studies focused on pure strains, the effect of heavy metals on ARG transfer in bacterial communities, especially in activated sludge, has not been clearly explored. In this study, a high-throughput method, combining computerized incubator (Bioscreen C) and flow cytometry, was developed to evaluate different concentrations of heavy metals influencing ARG transfer in sludge bacteria communities. By using Escherichia coli MG1655 as the donor of broad-host range IncP-1 plasmid pKJK5, it was found that 0.5 mmol/L Pb, 0.1 mmol/L As and 0.005 mmol/L Hg could obviously promote ARG transfer in sludge bacteria communities. Furthermore, mating assays on microfluidic chips also proved higher transfer frequencies in attached communities under the above heavy metal stresses. Transconjugants under Pb, As and Hg stresses were isolated and phylogenetically described. For As and Hg, the dominant genus was Pseudomonas, accounting for 88% and 96%, respectively. While under Pb stress, the genera Aeromonas and Enterobacter were the main transconjugants, accounting for 56% and 32% respectively. Moreover, ABC transporters and Amino acid metabolism, which were related to heavy metal transport and cellular metabolism, were dominant in the prediction of microbial metabolic function of transconjugants. This study can be helpful for risk assessment and control of ARG spreading in WWTPs. | 2019 | 31425984 |
| 3843 | 6 | 0.9998 | Bacterivorous Ciliate Tetrahymena pyriformis Facilitates vanA Antibiotic Resistance Gene Transfer in Enterococcus faecalis. Background: Wastewater treatment plants (WWTPs) are hotspots for the emergence and spread of antibiotic resistance genes (ARGs). In activated sludge treatment systems, bacterivorous protozoa play a crucial role in biological processes, yet their impact on the horizontal gene transfer in Gram-positive enteric bacteria remains largely unexplored. This study investigated whether the ciliate Tetrahymena pyriformis facilitates the transfer of antibiotic resistance genes between Enterococcus faecalis strains. Methods: Conjugation assays were conducted under laboratory conditions using a vanA-carrying donor and a rifampicin-resistant recipient at an initial bacterial concentration of 10(9) CFU/mL and ciliate density of 10(5) N/mL. Results: Transconjugant numbers peaked at 2 h when experiments started with recipient bacteria harvested in the exponential growth phase, and at 24 h when bacteria were in the stationary phase. In both cases, vanA gene transfer frequency was highest at 24 h (10(-4)-10(-5) CFU/mL), and the presence of energy sources increased gene transfer frequency by one order of magnitude. Conclusions: These findings suggest that ciliate grazing may contribute to vanA gene transfer in WWTP effluents, potentially facilitating its dissemination among permissive bacteria. Given the ecological and public health risks associated with vanA gene persistence in wastewater systems, understanding protozoan-mediated gene transfer is crucial for mitigating the spread of antibiotic resistance in aquatic environments. | 2025 | 40426515 |
| 7400 | 7 | 0.9998 | Investigating the effects of municipal and hospital wastewaters on horizontal gene transfer. Horizontal gene transfer (HGT) plays an important role in the dissemination of antibiotic resistance genes. In sewer systems, human-associated and environmental bacteria are mixed together and exposed to many substances known to increase HGT, including various antibacterial compounds. In wastewaters, those substances are most often detected below concentrations known to induce HGT individually. Still, it is possible that such wastewaters induce HGT, for example via mixture effects. Here, a panel of antibiotics, biocides and other pharmaceuticals was measured in filter-sterilized municipal and hospital wastewater samples from Gothenburg, Sweden. The effects on HGT of the chemical mixtures in these samples were investigated by exposing a complex bacterial donor community together with a GFP-tagged E. coli recipient strain. Recipients that captured sulfonamide resistance-conferring mobile genetic elements (MGEs) from the bacterial community were enumerated and characterized by replicon typing, antibiotic susceptibility testing and long read sequencing. While exposure to municipal wastewater did not result in any detectable change in HGT rates, exposure to hospital wastewater was associated with an increase in the proportion of recipients that acquired sulfonamide resistance but also a drastic decrease in the total number of recipients. Although, concentrations were generally higher in hospital than municipal wastewater, none of the measured substances could individually explain the observed effects of hospital wastewater. The great majority of the MGEs captured were IncN plasmids, and resistance to several antibiotics was co-transferred in most cases. Taken together, the data show no evidence that chemicals present in the studied municipal wastewater induce HGT. Still, the increased relative abundance of transconjugants after exposure to hospital wastewater could have implications for the risks of both emergence and transmission of resistant bacteria. | 2021 | 33631686 |
| 6767 | 8 | 0.9998 | Effects of iron mineral adhesion on bacterial conjugation: Interfering the transmission of antibiotic resistance genes through an interfacial process. Bacterial conjugation is one of the most prominent ways for antibiotic resistance genes (ARGs) transmission in the environment. Interfacial interactions between natural colloidal minerals and bacteria can alter the effective contact of bacteria, thereby affecting ARGs conjugation. Understanding the impact of iron minerals, a core component of colloidal minerals, on ARGs conjugation can help assess and intervene in the risk of ARGs transmission. With three selected iron minerals perturbation experiments, it was found that the conjugative transfer of plasmid that carried kanamycin resistance gene was 1.35 - 3.91-fold promoted by low concentrations of iron minerals (i.e., 5 - 100 mg L(-1)), but inhibited at high concentrations (i.e., 1000 - 2000 mg L(-1)) as 0.10 - 0.22-fold. Conjugation occurrence was highly relevant to the number of bacteria adhering per unit mass of mineral, thus switch in the adhesion modes of mineral-bacterial determined whether the conjugate transfer of ARGs was facilitated or inhibited. In addition, a unified model was formularized upon the physicochemical and physiological effects of adhesion on conjugation, and it can be used in estimating the critical inhibitory concentration of different iron minerals on conjugation. Our findings indicate natural colloidal minerals have great potential for applications in preventing the environmental propagation of ARGs through interfacial interactions. | 2022 | 35472548 |
| 3860 | 9 | 0.9998 | Mobility of antibiotic resistance and its co-occurrence with metal resistance in pathogens under oxidative stress. The bacterial communities are challenged with oxidative stress during their exposure to bactericidal antibiotics, metals, and different levels of dissolved oxygen (DO) encountered in diverse environmental habitats. The frequency of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) co-selection is increased by selective pressure posed by oxidative stress. Hence, study of resistance acquisition is important from an evolutionary perspective. To understand the dependence of oxidative stress on the dissemination of ARGs and MRGs through a pathogenic bacterial population, 12 metagenomes belonging to gut, water and soil habitats were evaluated. The metagenome-wide analysis showed the chicken gut to pose the most diverse pool of ARGs (30.4 ppm) and pathogenic bacteria (Simpson diversity = 0.98). The most common types of resistances found in all the environmental samples were efflux pumps (13.22 ppm) and genes conferring resistance to vancomycin (12.4 ppm), tetracycline (12.1 ppm), or beta-lactam (9.4 ppm) antibiotics. Additionally, limiting DO level in soil was observed to increase the abundance of excision nucleases (uvrA and uvrB), DNA polymerase (polA), catalases (katG), and other oxidative stress response genes (OSGs). This was further evident from major variations occurred in antibiotic efflux genes due to the effect of DO concentration on two human pathogens, namely Salmonella enterica and Shigella sonnei found in all the selected habitats. In conclusion, the microbial community, when challenged with oxidative stress caused by environmental variations in oxygen level, tends to accumulate higher amounts of ARGs with increased dissemination potential through triggering non-lethal mutagenesis. Furthermore, the genetic linkage or co-occurrence of ARGs and MRGs provides evidence for selecting ARGs under high concentrations of heavy metals. | 2021 | 34298350 |
| 3680 | 10 | 0.9998 | Metagenomic Insights Into the Contribution of Phages to Antibiotic Resistance in Water Samples Related to Swine Feedlot Wastewater Treatment. In this study, we examined the types of antibiotic resistance genes (ARGs) possessed by bacteria and bacteriophages in swine feedlot wastewater before and after treatment using a metagenomics approach. We found that the relative abundance of ARGs in bacterial DNA in all water samples was significantly higher than that in phages DNA (>10.6-fold), and wastewater treatment did not significantly change the relative abundance of bacterial- or phage-associated ARGs. We further detected the distribution and diversity of the different types of ARGs according to the class of antibiotics to which they confer resistance, the tetracycline resistance genes were the most abundant resistance genes and phages were more likely to harbor ATP-binding cassette transporter family and ribosomal protection genes. Moreover, the colistin resistance gene mcr-1 was also detected in the phage population. When assessing the contribution of phages in spreading different groups of ARGs, β-lactamase resistance genes had a relatively high spreading ability even though the abundance was low. These findings possibly indicated that phages not only could serve as important reservoir of ARG but also carry particular ARGs in swine feedlot wastewater, and this phenomenon is independent of the environment. | 2018 | 30459724 |
| 3853 | 11 | 0.9998 | Co-selection of antibiotic-resistant bacteria in a paddy soil exposed to As(III) contamination with an emphasis on potential pathogens. The increased acquisition of antibiotic resistance by pathogens is a global health concern. The environmental selection of antibiotic resistance can be caused by either antibiotic residues or co-selecting agents such as toxic metal(loid)s. This study explored the potential role of As(III) as a co-selecting driver in the spread of antibiotic resistance in paddy soils. By applying high-throughput sequencing, we found that the diversity and composition of soil microbial communities was significantly altered by As(III) exposure, resulting in an increased proportion of potential pathogens (9.9%) compared to the control soil (0.1%). Meanwhile, a total of 46 As(III)-resistant isolates were obtained from As(III)-exposure soil, among which potential pathogens accounted for 54.3%. These As(III)-resistant bacteria showed a high incidence of resistance to sulfanilamide (100%) and streptomycin (88-93%). The association between antibiotic and As(III) resistances was further investigated in a potentially pathogenic isolate by whole-genome sequencing and a transcription assay. The results showed that As(III) and antibiotic resistance genes might co-occur in a mobile genomic island and be co-regulated by As(III), implying that antibiotic resistance could be co-selected by As(III) via co-resistance and co-regulation mechanisms. Overall, these results suggest that As(III) exposure provides a strong selective pressure for the expansion of soil bacterial resistome. | 2020 | 32302839 |
| 3422 | 12 | 0.9998 | Exploring the Role of Coliform Bacteria in Class 1 Integron Carriage and Biofilm Formation During Drinking Water Treatment. This study investigates the role of coliforms in the carriage of class 1 integron and biocide resistance genes in a drinking water treatment plant and explores the relationship between the carriage of such genes and the biofouling abilities of the strain. The high incidence of class 1 integron and biocide resistance genes (33.3 % of the isolates) highlights the inherent risk of genetic contamination posed by coliform populations during drinking water treatment. The association between the presence of intI1 gene and qac gene cassettes, especially qacH, was greater in biofilm cells. In coliforms recovered from biofilms, a higher frequency of class 1 integron elements and higher diversity of genetic patterns occurred, compared to planktonic cells. The coliform isolates under the study proved to mostly carry non-classical class 1 integrons lacking the typical qacEΔ1/sul1 genes or a complete tni module, but bearing the qacH gene. No link was found between the carriage of integron genes and the biofouling degree of the strain, neither in aerobic or in anaerobic conditions. Coliform bacteria isolated from established biofilms rather adhere in oxygen depleted environments, while the colonization ability of planktonic cells is not significantly affected by oxygen availability. | 2016 | 27079455 |
| 6768 | 13 | 0.9998 | Biofilm formation mechanisms of mixed antibiotic-resistant bacteria in water: Bacterial interactions and horizontal transfer of antibiotic-resistant plasmids. Over 95 % of bacteria on water supply pipeline surfaces exist in biofilms, which are hotspots for antibiotic resistance gene (ARG) transmission. This study established mixed biofilm culture systems on a metal iron substrate using Escherichia coli: antibiotic-sensitive bacteria (ASB) and antibiotic-resistant bacteria (ARB). The growth rate and extracellular polymeric substances (EPS) content of mixed biofilm surpassed single-species biofilms due to synergistic interactions among different bacteria. However, the composition of mixed biofilms formed by ASB and ARB became unstable after 72 h, linked to reduced polysaccharide proportions in EPS and inter-bacterial competition. The bacterial composition and conjugative transfer frequency of ARGs in mixed biofilms indicate that biofilm formation significantly enhances horizontal transfer of ARGs. Notably, the conjugative transfer frequency of the mixed biofilm formed by two ARB increased 100-fold within five days. In contrast, the conjugative transfer frequency in the mixed biofilm formed by ASB and ARB was unstable; inter-bacterial competition led to plasmid loss associated with horizontal transfer of ARGs, ultimately resulting in biofilm shedding. Furthermore, genes associated with ARG transfer and biofilm growth up-regulated by 1.5 - 6 and 2 - 7 times, respectively, in mixed biofilm. These findings highlight a mutually reinforcing relationship between biofilm formation and horizontal ARG transmission, with significant environmental implications. | 2025 | 39566460 |
| 7528 | 14 | 0.9998 | Horizontal transfer of antibiotic resistance genes in a membrane bioreactor. Growing attention has been paid to the dissemination of antibiotic resistance genes (ARGs) in wastewater microbial communities. The application of membrane bioreactors (MBRs) in wastewater treatment is becoming increasingly widespread. We hypothesized that the transfer of ARGs among bacteria could occur in MBRs, which combine a high density of bacterial cells, biofilms, and antibiotic resistance bacteria or ARGs. In this study, the transfer discipline and dissemination of the RP4 plasmid in MBRs were investigated by the counting plate method, the MIDI microorganism identification system, and quantitative polymerase chain reaction (qPCR) techniques. The results showed that the average transfer frequency of the RP4 plasmid from the donor strain to cultivable bacteria in activated sludge was 2.76×10⁻⁵ per recipient, which was greater than the transfer frequency in wastewater and bacterial sludge reported previously. In addition, many bacterial species in the activated sludge had received RP4 by horizontal transfer, while the genera of Shewanella spp., Photobacterium spp., Pseudomonas spp., Proteus spp., and Vibrio spp. were more likely to acquire this plasmid. Interestingly, the abundance of the RP4 plasmid in total DNA remained at high levels and relatively stable at 10⁴ copies/mg of biosolids, suggesting that ARGs were transferred from donor strains to activated sludge bacteria in our study. Thus, the presence of ARGs in sewage sludge poses a potential health threat. | 2013 | 23942379 |
| 7384 | 15 | 0.9998 | Uncovering antimicrobial resistance in three agricultural biogas plants using plant-based substrates. Antimicrobial resistance (AMR) is becoming an increasing global concern and the anaerobic digestion (AD) process represents a potential transmission route when digestates are used as fertilizing agents. AMR contaminants, e.g. antibiotic-resistant bacteria (ARB) and plasmid-mediated antibiotic resistance genes (ARGs) have been found in different substrates and AD systems, but not yet been investigated in plant-based substrates. AMR transfer from soils to vegetable microbiomes has been observed, and thus crop material potentially represents a so far neglected AMR load in agricultural AD processes, contributing to AMR spread. In order to test this hypothesis, this study examined the AMR situation throughout the process of three biogas plants using plant-based substrates only, or a mixture of plant-based and manure substrates. The evaluation included a combination of culture-independent and -dependent methods, i.e., identification of ARGs, plasmids, and pathogenic bacteria by DNA arrays, and phylogenetic classification of bacterial isolates and their phenotypic resistance pattern. To our knowledge, this is the first study on AMR in plant-based substrates and the corresponding biogas plant. The results showed that the bacterial community isolated from the investigated substrates and the AD processing facilities were mainly Gram-positive Bacillus spp. Apart from Pantoea agglomerans, no other Gram-negative species were found, either by bacteria culturing or by DNA typing array. In contrast, the presence of ARGs and plasmids clearly indicated the existence of Gram-negative pathogenic bacteria, in both substrate and AD process. Compared with substrates, digestates had lower levels of ARGs, plasmids, and culturable ARB. Thus, digestate could pose a lower risk of spreading AMR than substrates per se. In conclusion, plant-based substrates are associated with AMR, including culturable Gram-positive ARB and Gram-negative pathogenic bacteria-associated ARGs and plasmids. Thus, the AMR load from plant-based substrates should be taken into consideration in agricultural biogas processing. | 2022 | 35306061 |
| 7398 | 16 | 0.9998 | Spread of chloramphenicol and tetracycline resistance genes by plasmid mobilization in agricultural soil. Spread of antibiotic resistance genes (ARGs) poses a worldwide threat to public health and food safety. However, ARG spread by plasmid mobilization, a broad host range transfer system, in agricultural soil has received little attention. Here, we investigated the spread of chloramphenicol resistance gene (CRG) and tetracycline resistance gene (TRG) in agricultural soil by mobilization of pSUP106 under different conditions, including different concentrations of nutrients, temperatures, soil depths, rhizosphere soils, and soil types. The number of resistant bacteria isolated in non-sterilized soil from the experiments was approximately 10(4) to 10(7) per gram of soil, belonging to 5-10 species from four genera, including nonpathogen, opportunistic pathogen, pathogen bacteria, and gram-positive and gram-negative bacteria, depending on the experiment conditions. In sterilized soil, higher levels of nutrients and higher temperatures promoted plasmid mobilization and ARG expression. Topsoil and deep soil might not support the spread of antibiotic resistance, while ARG dissemination by plasmid mobilization was better supported by maize rhizosphere and loam soils. All these factors might change bacterial growth and the activity of bacteria and lead to the above influence. Introduction of only the donor and helper, or the donor alone also resulted in the transfer of ARGs and large numbers of antibiotic resistant bacteria (ARB), indicating that some indigenous bacteria contain the elements necessary for plasmid mobilization. Our results showed that plasmid mobilization facilitated dissemination of ARGs and ARB in soil, which led to the disturbance of indigenous bacterial communities. It is important to clear ARG dissemination routes and inhibit the spread of ARGs. | 2020 | 31991360 |
| 7201 | 17 | 0.9998 | Evolution of microbial community and drug resistance during enrichment of tetracycline-degrading bacteria. Recently, the microbial degradation of tetracycline has been widely reported. However, its potential risks in treating wastewater containing high concentrations of tetracycline have not been fully evaluated. In this study, the evolution of the microbial community and drug resistance was traced during the enrichment of tetracycline-degrading bacteria. The results showed that some minor compositions such as Shewanella, Bacillus, and Pseudomonas in the seed sludge became the predominant genera in the enrichment cultures when continuously using tetracycline as the sole carbon source, especially some possible pathogenic bacteria increased significantly in this process. The abundances of most TRGs/16S rDNA were increased after enrichment, although the relative abundance of tetA and tetL genes decreased to some extent. From the enrichment culture, 7 predominant tetracycline-degrading strains were isolated, of which TD-1 (Bacillus) and TD-5 (Shewanella) presented high degradation efficiencies (6-day degradation rate > 95%, half-life period of tetracycline ≈ 24 h). In addition, multiple TRGs, mobile genetic elements (MGEs) and even gene cassettes were found in each tetracycline-degrading isolate. The findings suggested that some risks such as the pathogenicity of isolates and the spread of ARGs should be considered when the biodegradation method is used to treat wastewater polluted with high concentrations of tetracycline. | 2019 | 30660087 |
| 7397 | 18 | 0.9998 | Persistence of naturally occurring antibiotic resistance genes in the bacteria and bacteriophage fractions of wastewater. The emergence and prevalence of antibiotic resistance genes (ARGs) in the environment is a serious global health concern. ARGs from bacteria can be mobilized by mobile genetic elements, and recent studies indicate that phages and phage-derived particles, among others, could play a role in the spread of ARGs through the environment. ARGs are abundant in the bacterial and bacteriophage fractions of water bodies and for successful transfer of the ARGs, their persistence in these environments is crucial. In this study, three ARGs (blaTEM, blaCTX-M and sul1) that naturally occur in the bacterial and phage fractions of raw wastewater were used to evaluate the persistence of ARGs at different temperatures (4 °C, 22 °C and 37 °C) and pH values (3, 7 and 9), as well as after various disinfection treatments (thermal treatment, chlorination and UV) and natural inactivation in a mesocosm. Gene copies (GC) were quantified by qPCR; then the logarithmic reduction and significance of the differences between their numbers were evaluated. The ARGs persisted for a long time with minimal reductions after all the treatments. In general, they showed greater persistence in the bacteriophage fraction than in the bacterial fraction. Comparisons showed that the ARGs persisted under conditions that reduced culturable Escherichia coli and infectious coliphages below the limit of detection. The prevalence of ARGs, particularly in the bacteriophage fraction, poses the threat of the spread of ARGs and their incorporation into a new bacterial background that could lead to the emergence of new resistant clones. | 2016 | 26978717 |
| 3859 | 19 | 0.9998 | Co-selection of antibiotic resistance via copper shock loading on bacteria from a drinking water bio-filter. Heavy metal contamination of source water frequently occurred in developing countries as a result of accidents. To address the problems, most of the previous studies have focused on engineering countermeasures. In this study, we investigated the effects of heavy metals, particularly copper, on the development of antibiotic resistance by establishing a copper shock loading test. Results revealed that co-selection occurred rapidly within 6 h. Copper, at the levels of 10 and 100 mg/L, significantly increased bacterial resistance to the antibiotics tested, including rifampin, erythromycin, kanamycin, and a few others. A total of 117 antimicrobial-resistance genes were detected from 12 types of genes, and the relative abundance of most genes (particularly mobile genetic elements intⅠand transposons) was markedly enriched by at least one fold. Furthermore, the copper shock loading altered the bacterial community. Numerous heavy metal and antibiotic resistant strains were screened out and enriched. These strains are expected to enhance the overall level of resistance. More noticeably, the majority of the co-selected antibiotic resistance could sustain for at least 20 h in the absence of copper and antimicrobial drugs. Resistance to vancomycin, erythromycin and lincomycin even could remain for 7 days. The prominent selection pressure by the copper shock loading implies that a real accident most likely poses similar impacts on the water environment. An accidental release of heavy metals would not only cause harm to the ecological environment, but also contribute to the development of bacterial antibiotic resistance. Broader concerns should be raised about the biological risks caused by sudden releases of pollutants by accidents. | 2018 | 29059628 |