Mechanism of antibiotic resistance spread during sub-lethal ozonation of antibiotic-resistant bacteria with different resistance targets. - Related Documents




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676001.0000Mechanism of antibiotic resistance spread during sub-lethal ozonation of antibiotic-resistant bacteria with different resistance targets. The increase and spread of antibiotic-resistant bacteria (ARB) in aquatic environments and the dissemination of antibiotic resistance genes (ARGs) greatly impact environmental and human health. It is necessary to understand the mechanism of action of ARB and ARGs to formulate measures to solve this problem. This study aimed to determine the mechanism of antibiotic resistance spread during sub-lethal ozonation of ARB with different antibiotic resistance targets, including proteins, cell walls, and cell membranes. ARB conjugation and transformation frequencies increased after exposure to 0-1.0 mg/L ozone for 10 min. During sub-lethal ozonation, compared with control groups not stimulated by ozone, the conjugative transfer frequencies of E. coli DH5α (CTX), E. coli DH5α (MCR), and E. coli DH5α (GEN) increased by 1.35-2.02, 1.13-1.58, and 1.32-2.12 times, respectively; the transformation frequencies of E. coli DH5α (MCR) and E. coli DH5α (GEN) increased by 1.49-3.02 and 1.45-1.92 times, respectively. When target inhibitors were added, the conjugative transfer frequencies of antibiotics targeting cell wall and membrane synthesis decreased 0.59-0.75 and 0.43-0.76 times, respectively, while that for those targeting protein synthesis increased by 1-1.38 times. After inhibitor addition, the transformation frequencies of bacteria resistant to antibiotics targeting the cell membrane and proteins decreased by 0.76-0.89 and 0.69-0.78 times, respectively. Cell morphology, cell membrane permeability, reactive oxygen species, and antioxidant enzymes changed with different ozone concentrations. Expression of most genes related to regulating different antibiotic resistance targets was up-regulated when bacteria were exposed to sub-lethal ozonation, further confirming the target genes playing a crucial role in the inactivation of different target bacteria. These results will help guide the careful utilization of ozonation for bacterial inactivation, providing more detailed reference information for ozonation oxidation treatment of ARB and ARGs in aquatic environments.202438810347
676210.9999Impacts of particle size and surface charge of ZnO on horizontal transformation of antibiotic resistance genes. The ever-growing antibiotic resistance in bacteria poses an enormous threat to public health and the environment. The horizontal transfer of antibiotic resistance genes (ARGs) is a major pathway for disseminating antibiotic resistance. As an inexpensive, nontoxic, and biocompatible material, ZnO with diverse sizes and surface properties have been prepared for widespread use. However, the effects and mechanisms of ZnO particles with different structural properties on the horizontal transfer of ARGs are not comprehensively understood. In this study, two groups of ZnO particles, one with the same size (93 nm) and different charge types (-9.5 and + 17.4 mV), and the other homogeneously positively charged but of different sizes (93, 215, and 2381 nm), were prepared. Their impacts on the horizontal transformation of ARGs mediated by plasmid pUC19 into E coli DH5α were investigated. In the positively charged group, the smallest ZnO nanoparticles at concentrations of 0.1-100 μg/mL induced 1.04-1.35 and 1.37-1.71-fold increases in transformation frequency when compared with that of the medium-sized and largest particles, respectively. In the similar-sized groups, positive ZnO promoted 1.06-1.32-fold increases than negative ZnO. Further investigation suggested that smaller and positive ZnO adsorbed more plasmids and correspondingly increased the uptake by recipient bacteria than that of larger and/or negative ZnO. In addition, the enhanced bacterial membrane permeability, ATP synthesis, and DNA replication were also accounted for the increased transformation. These results suggest that smaller-sized and positive ZnO poses a high environmental risk of spreading antibiotic resistance.202540527433
780020.9998Effects of ultraviolet disinfection on antibiotic-resistant Escherichia coli from wastewater: inactivation, antibiotic resistance profiles and antibiotic resistance genes. AIMS: To evaluate the effect of ultraviolet (UV) disinfection on antibiotic-resistant Escherichia coli. METHODS AND RESULTS: Antibiotic-resistant E. coli strains were isolated from a wastewater treatment plant and subjected to UV disinfection. The effect of UV disinfection on the antibiotic resistance profiles and the antibiotic resistance genes (ARGs) of antibiotic-resistant E. coli was evaluated by a combination of antibiotic susceptibility analysis and molecular methods. Results indicated that multiple-antibiotic-resistant (MAR) E. coli were more resistant at low UV doses and required a higher UV dose (20 mJ cm(-2) ) to enter the tailing phase compared with those of antibiotic-sensitive E. coli (8 mJ cm(-2) ). UV disinfection caused a selective change in the inhibition zone diameters of surviving antibiotic-resistant E. coli and a slight damage to ARGs. The inhibition zone diameters of the strains resistant to antibiotics were more difficult to alter than those susceptible to antibiotics because of the existence and persistence of corresponding ARGs. CONCLUSIONS: The resistance of MAR bacteria to UV disinfection at low UV doses and the changes in inhibition zone diameters could potentially contribute to the selection of antibiotic-resistant bacteria in wastewater treatment after UV disinfection. The risk of spread of antibiotic resistance still exists owing to the persistence of ARGs. SIGNIFICANCE AND IMPACT OF THE STUDY: Our study highlights the acquisition of other methods to control the spread of ARGs.201728459506
676130.9998Exposure to Al(2)O(3) nanoparticles facilitates conjugative transfer of antibiotic resistance genes from Escherichia coli to Streptomyces. The spread of antibiotic resistance genes (ARGs) has become a global environmental issue; it has been found that nanoparticles (NPs) can promote the transfer of ARGs between bacteria. However, it remains unclear whether NPs can affect this kind of conjugation in Streptomyces, which mainly conjugate with other bacteria via spores. In the present study, we demonstrated that Al(2)O(3) NPs significantly promote the conjugative transfer of ARGs from Escherichia coli (E. coli) ET12567 to Streptomyces coelicolor (S. coelicolor) M145 without the use of heat shock method. The number of transconjugants induced by Al(2)O(3) particles was associated with the size and concentration of Al(2)O(3) particles, exposure time, and the ratio of E. coli and spores. When nanoparticle size was 30 nm at a concentration of 10 mg/L, the conjugation efficiency reached a peak value of 182 cfu/10(8) spores, which was more than 60-fold higher than that of the control. Compared with nanomaterials, bulk particles exhibited no significant effect on conjugation efficiency. We also explored the mechanisms by which NPs promote conjugative transfer. After the addition of NPs, the intracellular ROS content increased and the expression of the classical porin gene ompC was stimulated. In addition, ROS enhanced the mRNA expression levels of conjugative genes by inhibiting global regulation genes. Meanwhile, expression of the conjugation-related gene intA was also stimulated, ultimately increasing the number of transconjugants. Our results indicated that Al(2)O(3) NPs significantly promoted the conjugative transfer of ARGs from bacteria to spores and aggravated the diffusion of resistance genes in the environment.201931561730
384740.9998The impact and mechanism of quaternary ammonium compounds on the transmission of antibiotic resistance genes. The emergence of antibiotic resistance genes (ARGs) in microbes can be largely attributed to the abuse and misuse of antibiotics and biocides. Quaternary ammonium compounds (QACs) have been used worldwide as common disinfectants and detergents; however, their potential impact on the spread and diffusion of ARGs is still unknown. In this study, we detected the QAC resistance gene (qacEΔ1), the 1 integron gene (intI1), and 12 ARGs (sul1, sul2, cfr, cml, fexA, tetA, tetG, tetQ, tetX, ermB, bla(TEM,) and dfrA1) in 48 water samples from three watersheds by quantitative PCR (qPCR). We investigated the evolution of bacterial antibiotic resistance under QAC and antibiotic environmental pressures by long-term continuous culture. In addition, five QACs were selected to investigate the effect of QAC on the efficiency of conjugation transfer. The changes in bacterial cell membrane and production of reactive oxygen species (ROS) were detected by flow cytometry, revealing the mechanism by which QAC affects the spread of antibiotic resistance. Our results showed that the QAC resistance gene was ubiquitous in watersheds and it had significant correlation with intI1 and seven ARGs (r = 0.999, p < 0.01). QACs could increase the resistance of bacteria to multiple antibiotics. Furthermore, all five QACs promoted the conjugation transfer of the RP4 plasmid; the optimal concentration of QACs was about 10(-1)-10(-2) mg/L and their transfer efficiencies were between 1.33 × 10(-6) and 8.87 × 10(-5). QACs enhanced membrane permeability of bacterial cells and stimulated bacteria to produce ROS, which potentially promoted the transfer of plasmids between bacteria. In conclusion, this study demonstrated that QACs may facilitate the evolution and gene transfer of antibiotic resistance gene among microbiome.201931372954
784550.9998Mechanism and potential risk of antibiotic resistant bacteria carrying last resort antibiotic resistance genes under electrochemical treatment. The significant rise in the number of antibiotic resistance genes (ARGs) that resulted from our abuse of antibiotics could do severe harm to public health as well as to the environment. We investigated removal efficiency and removal mechanism of electrochemical (EC) treatment based on 6 different bacteria isolated from hospital wastewater carrying 3 last resort ARGs including NDM-1, mcr-1 and tetX respectively. We found that the removal efficiency of ARGs increased with the increase of both voltage and electrolysis time while the maximum removal efficiency can reach 90%. The optimal treatment voltage and treatment time were 3 V and 120 min, respectively. Temperature, pH and other factors had little influence on the EC treatment process. The mechanism of EC treatment was explored from the macroscopic and microscopic levels by scanning electron microscopy (SEM) and flow cytometry. Our results showed that EC treatment significantly changed the permeability of cell membrane and caused cells successively experience early cell apoptosis, late cell apoptosis and cell necrosis. Moreover, compared with traditional disinfection methods, EC treatment had less potential risks. The conjugative transfer frequencies of cells were significantly reduced after treatment. Less than 1% of bacteria entered the viable but nonculturable (VBNC) state and less than 5% of intracellular ARGs (iARGs) turned into extracellular ARGs (eARGs). Our findings provide new insights into as well as important reference for future electrochemical treatment in removing ARB from hospital wastewater.202235085630
780160.9998Disinfection of swine wastewater using chlorine, ultraviolet light and ozone. Veterinary antibiotics are widely used at concentrated animal feeding operations (CAFOs) to prevent disease and promote growth of livestock. However, the majority of antibiotics are excreted from animals in urine, feces, and manure. Consequently, the lagoons used to store these wastes can act as reservoirs of antibiotics and antibiotic-resistant bacteria. There is currently no regulation or control of these systems to prevent the spread of these bacteria and their genes for antibiotic resistance into other environments. This study was conducted to determine the disinfection potential of chlorine, ultraviolet light and ozone against swine lagoon bacteria. Results indicate that a chlorine dose of 30 mg/L could achieve a 2.2-3.4 log bacteria reduction in lagoon samples. However, increasing the dose of chlorine did not significantly enhance the disinfection activity due to the presence of chlorine-resistant bacteria. The chlorine resistant bacteria were identified to be closely related to Bacillus subtilis and Bacillus licheniformis. A significant percentage of lagoon bacteria were not susceptible to the four selected antibiotics: chlortetracycline, lincomycin, sulfamethazine and tetracycline (TET). However, the presence of both chlorine and TET could inactivate all bacteria in one lagoon sample. The disinfection potential of UV irradiation and ozone was also examined. Ultraviolet light was an effective bacterial disinfectant, but was unlikely to be economically viable due to its high energy requirements. At an ozone dose of 100 mg/L, the bacteria inactivation efficiency could reach 3.3-3.9 log.200616678233
384870.9998Effect 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.202438830804
779980.9998Combating Staphylococcus aureus and its methicillin resistance gene (mecA) with cold plasma. The increase in antibiotic resistance has become a global challenge to public health. In this study, an atmospheric cold plasma (ACP) system was applied for combating methicillin-resistant Staphylococcus aureus (MRSA) and its methicillin resistance gene (mecA) during food wastewater treatment. The plate count and flow cytometry methods were employed to estimate the damage in MRSA induced by plasma treatment. A quantitative real-time PCR (qPCR) method was used to assess the plasma-induced degradation of the mecA genes. The inactivation of MRSA and degradation of extracellular (e-) and intracellular (i-)mecA genes were investigated in phosphate buffered solution as a function of plasma exposure. A relatively low plasma influence of 0.12 kJ/cm(2) accounted for 5-log MRSA and 1.4-log e-mecA genes reduction, while only around 0.19-log degradation for i-mecA genes. As the plasma intensity was accumulated to 0.35 kJ/cm(2), the reduction of e- and i-mecA genes was increased to 2.6 and 0.8 logs, respectively. The degradation of i-mecA genes was much slower than that of e-mecA genes due to the protective effects of the outer envelopes or intracellular components against plasma. The matrix effect of wastewater effluents shielded both antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) from plasma disinfection, which led to a lower degradation efficacy. Our results could support the development and optimization of plasma-based wastewater treatment.201830248853
784790.9998Inactivation and change of tetracycline-resistant Escherichia coli in secondary effluent by visible light-driven photocatalytic process using Ag/AgBr/g-C(3)N(4). Control of antibiotic-resistant bacteria (ARB) and their related genes in secondary effluents has become a serious issue because of increased awareness of their health risks. A considerable number of techniques have been developed in recent years, particularly in relation to advanced oxidation. However, limited information is known about cellular behavior and resistance characteristic change during photocatalytic treatment. In this study, the inactivation of tetracycline (TC)-resistant Escherichia coli (TC-E. coli), removal of TC-resistant genes (TC-RGs), and antibiotic susceptibility were evaluated by employing photocatalytic treatment using Ag/AgBr/g-C(3)N(4) with visible light irradiation. The effects of light intensity, photocatalyst dosage, and reaction ambient temperature on photocatalysis were modelled and investigated. The rate of TC-E. coli removal was also optimized. Results demonstrated that the optimal conditions for TC-E. coli removal included light intensity of 96.0 mW/cm(2), photocatalyst dosage of 211.0 mg/L, and reaction ambient temperature of 23.7 °C. Under such conditions, the ARB removal rate was 6.1 log after 90 min and the related TC-RG removal rates were 49%, 86%, 69%, and 86% for tetA, tetM, tetQ, and intl1, respectively. The minimum inhibitory concentration test after photocatalysis shows that the antibiotic resistance of TC-E. coli was enhanced, which may be mainly due to the changes in the membrane potential and resulted in difficulty in destroying the bacteria through antibiotic contact. Hence, photocatalytic treatment could be an ideal method for ARB and antibiotic-resistant gene (ARG) control in wastewater, but the health risks of the remaining ARB and ARG should be investigated further.202031841919
6749100.9998The influence of ZnO nanoparticles on horizontal transfer of resistance genes in lab and soil conditions. Antibiotic resistance is a severe problem that threatens the achievements of modern medicine. Metallic nanoparticles may promote the horizontal transfer of resistance genes due to their toxicity to bacterial cells and metal-induced co-selection mechanisms. In this study, we investigated the toxicity of ZnO nanoparticles to E. coli DH5α laboratory strain and the abundance of soil microbial community. Moreover, the influence of ZnO nanoparticles on resistance gene transfer in laboratory and soil conditions was evaluated. ZnO nanoparticles at concentrations up to 10 mg L(-1) reduced the survival of E. coli cells by 14.6% and increased the transformation frequency by almost 1.8 fold. In soil, ZnO nanoparticles at a concentration of 1000 mg kg(-1) affected the total abundance of bacteria, causing a decrease in the 16S rRNA gene copy number. We did not detect the presence of 11 target antibiotic resistance genes (sul1, sul2, imp2, imp5, bla(CTX-M), ermB, mefA, strB, aadA1, tetA1, tetB), which confer resistance to five classes of antibiotics in soil treated with ZnO nanoparticles. No elevated conjugation frequency was observed in soil microbial communities treated with ZnO nanoparticles. However, the increase in czcA gene copies indicates the spread of genetic elements harbouring metal resistance. The data shows that metallic nanoparticles promote the spread of antibiotic and metal resistance genes. The broad implication of the present research is that the inevitable nanoparticles environmental pollution may lead to the further dissemination of antibiotic resistance and profoundly influence public health.202336764431
7784110.9998No evidential correlation between veterinary antibiotic degradation ability and resistance genes in microorganisms during the biodegradation of doxycycline. Biodegradation of antibiotic residues in the environment by microorganisms may lead to the generation of antibiotic resistance genes (ARGs), which are of great concern to human health. The aim of this study was to determine whether there is a relationship between the ability to degrade antibiotic doxycycline (DOX) and the development of resistance genes in microorganisms. We isolated and identified ten bacterial strains from a vegetable field that had received long-term manure application as fertilizer and were capable of surviving in a series of DOX concentrations (25, 50, 80, and 100mg/L). Our results showed no evidential correlation between DOX degradation ability and the development of resistance genes among the isolated microorganisms that had high DOX degradation capability (P > 0.05). This was based on the fact that Escherichia sp. and Candida sp. were the most efficient bacterial strains to degrade DOX (92.52% and 91.63%, respectively), but their tetracycline resistance genes showed a relatively low risk of antibiotic resistance in a 7-day experiment. Moreover, the tetM of the ribosomal protection protein genes carried by these two preponderant bacteria was five-fold higher than that carried by other isolates (P < 0.05). Pearson correlations between the C(t)/C(0) of DOX and tet resistance genes of three isolates, except for Escherichia sp. and Candida sp., showed remarkable negative correlations (P < 0.05), mainly because tetG markedly increased during the DOX degradation process. Our results concluded that the biodegradation of antibiotic residues may not necessarily lead to the development of ARGs in the environment. In addition, the two bacteria that we isolated, namely, Escherichia sp. and Candida sp., are potential candidates for the engineering of environmentally friendly bacteria.201828942279
8500120.9998Plasma induced efficient removal of antibiotic-resistant Escherichia coli and antibiotic resistance genes, and inhibition of gene transfer by conjugation. Antibiotic-resistant bacteria (ARB) and their resistance genes (ARGs) are emerging environmental pollutants that pose great threats to human health. In this study, a novel strategy using plasma was developed to simultaneously remove antibiotic-resistant Escherichia coli (AR bio-56954 E. coli) and its ARGs, aiming to inhibit gene transfer by conjugation. Approximately 6.6 log AR bio-56954 E. coli was inactivated within 10 min plasma treatment, and the antibiotic resistance to tested antibiotics (tetracycline, gentamicin, and amoxicillin) significantly decreased. Reactive oxygen and nitrogen species (RONS) including •OH, (1)O(2), O(2)•(-), NO(2)(-), and NO(3)(-) contributed to ARB and ARGs elimination; their attacks led to destruction of cell membrane, accumulation of excessive intracellular reactive oxygen substances, deterioration of conformational structures of proteins, and destroy of nucleotide bases of DNA. As a result, the ARGs (tet(C), tet(W), blaTEM-1, aac(3)-II), and integron gene intI1), and conjugative transfer frequency of ARGs significantly decreased after plasma treatment. The results demonstrated that plasma has great prospective application in removing ARB and ARGs in water, inhibiting gene transfer by conjugation.202134214852
7629130.9998Graphene oxide in the water environment could affect tetracycline-antibiotic resistance. In recent years, the influence of new materials like nanoparticles in the water environment on biological substances has been widely studied. Antibiotic resistance genes (ARGs) represent a new type of pollutant in the environment. Graphene oxide (GO), as a nano material, because of its unique structure, may have an impact on antibiotic resistance bacteria (ARB) and ARGs; however the research in this area is rarely reported. Therefore, this study mainly investigated the effects of GO on bacterial antibiotic resistance. The results showed that GO had a limited effect on ARB inactivation. A high concentration of GO (>10 mg/L) can damage resistant plasmids to reduce bacterial resistance to antibiotics, but low concentrations of GO (<1 mg/L) led to almost no damage to the plasmid. However, all tested concentrations of GO promoted the conjugative transfer from 1to over 3 folds, with low concentrations and high concentration (1-10 and 100 mg/L) of GO samples the least promoted. The overall effect of GO on antibiotic resistance needs further investigation.201728549325
7808140.9998Visible light-driven C/O-g-C(3)N(4) activating peroxydisulfate to effectively inactivate antibiotic resistant bacteria and inhibit the transformation of antibiotic resistance genes: Insights on the mechanism. Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) dissemination within water pose a serious threat to public health. Herein, C and O dual-doped g-C(3)N(4) (C/O-g-C(3)N(4)) photocatalyst, fabricated via calcination treatment, was utilized to activate peroxydisulfate (PDS) to investigate the disinfection effect on tetracycline-resistant Escherichia coli and the transformation frequency of ARGs. As a result, approximately 7.08 log E. coli were inactivated, and 72.36 % and 53.96 % of antibiotics resistance gene (tetB) and 16 S rRNA were degraded respectively within 80 min. Futhermore, the transformation frequency was reduced to 0.8. Characterization and theoretical results indicated that C and O doping in g-C(3)N(4) might lead to the electronic structure modulation and band gap energy reduction, resulting in the production of more free radicals. The mechanism analysis revealed that C/O-g-C(3)N(4) exhibited a lower adsorption energy and reaction energy barrier for PDS compared to g-C(3)N(4). This was beneficial for the homolysis of O-O bonds, forming SO(4)(•-) radicals. The attack of the generated active species led to oxidative stress in cells, resulting in damage to the electron transport chain and inhibition of ATP production. Our findings disclose a valuable insight for inactivating ARB, and provide a prospective strategy for ARGs dissemination in water contamination.202437976858
3845150.9998A 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.201829909325
7807160.9997Copper oxide/peroxydisulfate system for urban wastewater disinfection: Performances, reactive species, and antibiotic resistance genes removal. In this study, copper oxide (CuO) catalyzed peroxydisulfate (PDS) system was investigated for the inactivation of a broad range of pathogenic microorganisms from urban wastewater. Complete inactivation of Escherichia coli, Enterococcus, F-specific RNA bacteriophages from secondary treated wastewater was achieved after a short time (15-30 min) treatment with CuO (10 g/L)/PDS (1 mM) system, but spores of sulfite-reducing bacteria took 120 min. No bacterial regrowth occurred during storage after treatment. Significant reduction of the pathogens was explained by the generation of the highly selective Cu(III) oxidant, as the predominant reactive species, which could quickly oxidize guanine through a one-electron oxidation pathway. Additionally, the potential of the CuO (10 g/L)/PDS (1 mM) system to inactivate antibiotic-resistant bacteria and antibiotic resistance genes (ARB&Gs) was explored. Sulfamethoxazole-resistant E. coli was used as the model ARB and a 3.2 log of reduction was observed after 10 min of treatment. A considerable reduction (0.7-2.3 log) of selected ARGs including blaTEM, qnrS, emrB, sul1, and genes related to the dissemination of antibiotic resistance, including the Class 1 integron-integrase (intI1), and the insertion sequence (IS613) was achieved after 60 min treatment. All these findings indicated the promising applicability of the CuO/PDS system as a disinfection technology for wastewater reuse in agriculture.202234648831
3844170.9997Effects of Nutrient Level and Growth Rate on the Conjugation Process That Transfers Mobile Antibiotic Resistance Genes in Continuous Cultures. Bacteria in the effluent of wastewater treatment plants (WWTPs) can transfer antibiotic resistance genes (ARGs) to the bacteria in receiving water through conjugation; however, there is a lack of quantitative assessment of this phenomenon in continuous cultures. Our objective was to determine the effects of background nutrient levels in river water column and growth rates of bacteria on the conjugation frequency of ARGs from effluent bacteria to river bacteria, as well as on the resulting resistance level (i.e., MICs) of the river bacteria. Chemostats were employed to simulate the discharge points of WWTPs into rivers, where effluent bacteria (donor cells) meet river bacteria (recipient cells). Both donor and recipient cells were Escherichia coli cells, and the donor cells were constructed by filter mating with bacteria in the effluent of a local WWTP. Results showed that higher bacterial growth rate (0.45 h(-1) versus 0.15 h(-1)) led to higher conjugation frequencies (10(-4) versus 10(-6) transconjugant per recipient). The nutrient level also significantly affected the conjugation frequency, albeit to a lesser extent than the growth rate. The MIC against tetracycline increased from 2 mg/L in the recipient to 64 to 128 mg/L in transconjugants. In comparison, the MIC only increased to as high as 8 mg/L in mutants. Whole-genome sequencing showed that the tet-containing plasmid in both the donor and the transconjugant cells also occur in other fecal bacterial genera. The quantitative information obtained from this study can inform hazard identification related to the proliferation of wastewater-associated ARGs in surface water. IMPORTANCE WWTPs have been regarded as an important hot spot of ARGs. The discharge point of WWTP effluent, where ARGs may be horizontally transferred from bacteria of treated wastewater to bacteria of receiving water, is an important interface between the human-dominated ecosystem and the natural environment. The use of batch cultures in previous studies cannot adequately simulate the nutrient conditions and growth rates in receiving water. In this study, chemostats were employed to simulate the continuous growth of bacteria in receiving water. Furthermore, the experimental setup allowed for separate investigations on the effects of nutrient levels (i.e., simulating background nutrients in river water) and bacterial growth rates on conjugation frequencies and resulting resistance levels. The study generates statistically sound ecological data that can be used to estimate the risk of wastewater-originated ARGs as part of the One Health framework.202236094214
7193180.9997Plasmid-mediated transfer of antibiotic resistance genes and biofilm formation in a simulated drinking water distribution system under chlorine pressure. The effects of disinfectants and plasmid-based antibiotic resistance genes (ARGs) on the growth of microorganisms and the plasmid-mediated transfer of ARGs in the water and biofilm of the drinking water distribution system under simulated conditions were explored. The heterotrophic plate count of the water in reactors with 0.1 mg/L NaClO and NH(2)Cl was higher than in the control groups. There was no similar phenomenon in biofilm. In the water of reactors containing NaClO, the aphA and bla genes were lower than in the antibiotic resistant bacteria group, while both genes were higher in the water of reactors with NH(2)Cl than in the control group. Chloramine may promote the transfer of ARGs in the water phase. Both genes in the biofilm of the reactors containing chlorine were lower than the control group. Correlation analysis between ARGs and water quality parameters revealed that the copy numbers of the aphA gene were significantly positively correlated with the copy numbers of the bla gene in water and significantly negatively correlated in biofilm (p < 0.05). The results of the sequencing assay showed that bacteria in the biofilm, in the presence of disinfectant, were primarily Gram-negative. 1.0 mg/L chlorine decreased the diversity of the community in the biofilm. The relative abundance of some bacteria that may undergo transfer increased in the biofilm of the reactor containing 0.1 mg/L chlorine.202539617560
7785190.9997Fate of Extracellular DNA in the Production of Fertilizers from Source-Separated Urine. The practice of urine source-separation for fertilizer production necessitates an understanding of the presence and impact of extracellular DNA in the urine. This study examines the fate of plasmid DNA carrying ampicillin and tetracycline resistance genes in aged urine, including its ability to be taken up and expressed by competent bacteria. Plasmid DNA incubated in aged urine resulted in a >2 log loss of bacterial transformation efficiency in Acinetobacter baylyi within 24 h. The concentration of ampicillin and tetracycline resistance genes, as measured with quantitative polymerase chain reaction, did not correspond with the observed transformation loss. When the plasmid DNA was incubated in aged urine that had been filtered (0.22 μm) or heated (75 °C), the transformation efficiencies were more stable than when the plasmids were incubated in unfiltered and unheated aged urine. Gel electrophoresis results indicated that plasmid linearization by materials larger than 100 kDa in the aged urine caused the observed transformation efficiency decreases. The results of this study suggest that extracellular DNA released into aged urine poses a low potential for the spread of antibiotic resistance genes to bacteria once it is released to the environment.202031965791