Removal Of Antibiotic-resistant Bacteria Research Articles

Modified activated carbon material-assisted electrochemical disinfection effectively inactivate antibiotic-resistant bacteria

ABSTRACT The production and widespread transmission of antibiotic-resistant bacteria (ARB) pose an emerging threat to global public health. Electrochemical disinfection (ED) is an environmentally friendly disinfection technology widely utilized to inactivate ARB. This study explored the effect of modified activated carbon material (MACM) assisted ED on multi-ARB inactivation and the regeneration ability. The established ED technique was proven to be effective in inactivating multi-resistant ARB. Specifically, a 5-log ARB removal was achieved within 30 min treatment of MACM-assisted ED at 2.5 V. Additionally, no ARB regrowth was observed, indicating a permanent inactivation of ARB. The high level of reactive chlorine induced by MACM electrolysis was stressful to the ARB. Reactive chlorine led to overproduction of reactive oxygen species and damage of cell membranes in cells, accelerating the inactivation of ARB. Conclusively, the MACM-assisted ED method demonstrated efficient performance for ARB inactivation, implying this method is a promising alternative to traditional disinfection methods in countering ARB transmission.

Narrow spectrum nano-antibiotic for selective removal of ARB from contaminated water: New insights into stimuli response based on cellular attachment, lysis, and excretion

Narrow spectrum nano-antibiotics are supposedly the future trouble-shooters to improve the efficacy of conventional antimicrobials for treatment of severe bacterial infections, remove contamination from water and diminish the development of antibiotic resistance. In this study, antimicrobial peptide functionalized boron-carbon-nitride nanosheets ((Ant)pep@BCN NSs) are developed that are a promising wastewater disinfector and antibiotic resistant bactericide agent. These nanosheets are developed for selective removal and effective inactivation of antibiotic resistant bacteria (ARB) from water in presence of two virulent bacteria. The (Ant)pep@BCN NSs provide reactive surface receptors specific to the ARB. They mimic muralytic enzymes to damage the cell membrane of ARB. These NSs demonstrate 3-fold higher antimicrobial efficiency against the targeted ARB compared to pristine BCN even at lower concentrations. To the best of our knowledge, this is the first time that functionalized BCN has been developed to remove ARB selectively from wastewater. Furthermore, the (Ant)pep@BCN selectively reduced the microbiological load and led to morphological changes in Gram negative ARB in a mixed bacterial inoculum. These ARBs excreted outer–inner membrane vesicles (OIMVs) of triangular shape as a stimuli response to (Ant)pep@BCN NSs. These novel antimicrobial peptide-NSs have potential to improve treatment efficacy against ARB infections and water contamination.

Removal of antibiotic resistant bacteria by the coupled system of ferrous ion activated peroxymonosulfate (PMS) and sodium percarbonate (SPC): Performance and mechanisms

Antibiotic resistance has turned into a focus of universal public health concern. Wastewater treatment plants are considered as reservoirs of antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs), which can be transmitted to the environment. In this research, an effective method for inactivating Escherichia coli DH5α (E. coli DH5α) carrying resistance genes was developed utilizing dual oxidant system of peroxymonosulfate (PMS) and sodium percarbonate (SPC) in the presence of ferrous ions (Fe(II)). The results indicated that E. coli DH5α could be inactivated 6.36 log under the conditions of 0.50 mM PMS, 0.50 mM SPC and 0.50 mM Fe(II) after 30 min. Besides, the removal of different types of ARB and pollutants could also be achieved by Fe(II)/PMS/SPC system. The quenching experiment and EPR analysis demonstrated that reactive species (•OH, SO4•−, O2•−, 1O2 and CO3•−) involved in the inactivation of E. coli DH5α. Bacterial damage mechanisms were systematically studied in terms of cell structure and morphology, enzyme activity, malondialdehyde and intracellular reactive oxygen species levels. The inactivation of E. coli DH5α in complex water matrix (including coexisting of anions and natural organic matter) and real wastewater was inhibited. The abundance of intracellular ARGs decreased by 1.15 log, whereas extracellular ARGs increased by 0.32 log. This research supplied a prospective approach for inhibiting the dissemination of antibiotic resistance.

Application of UV LEDs to inactivate antibiotic resistant bacteria: Kinetics, efficiencies, and reactivations

Unregulated antibiotic use has led to the proliferation of antibiotic-resistant bacteria (ARB) in aquatic environments. Ultraviolet light-emitting diodes (UV LEDs) have evolved as an innovative technology for inactivating microorganisms offering several advantages over traditional mercury lamps. This research concentrated on utilizing UV LEDs with three distinct wavelengths (265 nm, 275 nm, and 285 nm) to inactivate E. coli DH10β encoding the ampicillin-resistant blaTEM-1 gene in its plasmid. Non-linear models, such as Geeraerd's and Weibull, provided more accurate characterization of the inactivation profiles than the traditional log-linear model due to the incorporation of both biological mechanisms and a deterministic approach within non-linear models. The inactivation rates of ARB were higher than antibiotic-sensitive bacteria (ASB) when subjected to UV LEDs. The highest inactivation rates were observed when all microorganisms were exposed to 265 nm. Photoreactivation emerged as the primary mechanism responsible for repairing DNA damage induced by UV LEDs. 285 nm showed the highest reactivation efficiencies for ARB under different fluences. At higher fluences, both 265 and 275 nm displayed similar effectiveness in suppressing reactivation, while at lower fluences, 275 nm exhibited better efficacies in controlling the reactivation. Therefore, the inhibition of reactivation was influenced by the extent of damage incurred by both DNA and enzymes. In nutrient-poor media (0.9 % NaCl), ASB did not exhibit any reactivation potential. However, the addition of Luria-Bertani (LB) broth promoted the reactivation of ASB. Lower fluence rate was more beneficial at 265 nm whereas higher fluence rates were more effective for longer wavelengths. The inactivation of ARB was enhanced by dissolved organic carbon (DOC) at low fluences. However, the removal of ARB was reduced due to the presence of DOC at higher fluences. The highest energy demand for ARB inactivation was reported at 285 nm. Environmental implicationThe excessive and unregulated utilization of antibiotics has emerged as a significant issue for public health. This paper presents a comprehensive analysis of the effectiveness of UV LEDs, an emerging technology, in the inactivation of antibiotic-resistant bacteria (ARB). This research paper explores the kinetics of UV LEDs with different wavelengths to inactivate ARB along with the reactivation efficiencies. This research work also explores the impact and relevant mechanisms of the impact of dissolved organic carbon (DOC) on the inactivation of ARB by UV LEDs.

Mechanisms for more efficient antibiotics and antibiotic resistance genes removal during industrialized treatment of over 200 tons of tylosin and spectinomycin mycelial dregs by integrated meta-omics

To mitigate the environmental risks posed by the accumulation of antibiotic mycelial dregs (AMDs), this study first attempted over 200 tons of mass production fermentation (MP) using tylosin and spectinomycin mycelial dregs alongside pilot-scale fermentation (PS) for comparison, utilizing the integrated-omics and qPCR approaches. Co-fermentation results showed that both antibiotics were effectively removed in all treatments, with an average removal rate of 92%. Antibiotic resistance gene (ARG)-related metabolic pathways showed that rapid degradation of antibiotics was associated with enzymes that inactivate macrolides and aminoglycosides (e.g., K06979, K07027, K05593). Interestingly, MP fermentations with optimized conditions had more efficient ARGs removal because homogenization permitted faster microbial succession, with more stable removal of antibiotic resistant bacteria and mobile genetic elements. Moreover, Bacillus reached 75% and secreted antioxidant enzymes that might inhibit horizontal gene transfer of ARGs. The findings confirmed the advantages of MP fermentation and provided a scientific basis for other AMDs.

Evaluating the Impact of Cl2•- Generation on Antibiotic-Resistance Contamination Removal via UV/Peroxydisulfate.

The removal of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) using sulfate anion radical (SO4•-)-based advanced oxidation processes has gained considerable attention recently. However, immense uncertainties persist in technology transfer. Particularly, the impact of dichlorine radical (Cl2•-) generation during SO4•--mediated disinfection on ARB/ARGs removal remains unclear, despite the Cl2•- concentration reaching levels notably higher than those of SO4•- in certain SO4•--based procedures applied to secondary effluents, hospital wastewaters, and marine waters. The experimental results of this study reveal a detrimental effect on the disinfection efficiency of tetracycline-resistant Escherichia coli (Tc-ARB) during SO4•--mediated treatment owing to Cl2•- generation. Through a comparative investigation of the distinct inactivation mechanisms of Tc-ARB in the Cl2•-- and SO4•--mediated disinfection processes, encompassing various perspectives, we confirm that Cl2•- is less effective in inducing cellular structural damage, perturbing cellular metabolic activity, disrupting antioxidant enzyme system, damaging genetic material, and inducing the viable but nonculturable state. Consequently, this diminishes the disinfection efficiency of SO4•--mediated treatment owing to Cl2•- generation. Importantly, the results indicate that Cl2•- generation increases the potential risk associated with the dark reactivation of Tc-ARB and the vertical gene transfer process of tetracycline-resistant genes following SO4•--mediated disinfection. This study underscores the undesired role of Cl2•- for ARB/ARGs removal during the SO4•--mediated disinfection process.

Efficient peroxymonosulfate activation by iron-cobalt bimetallic biochar for rapid removal of antibiotic resistant bacteria, antibiotic resistance genes, and ampicillin: The coexisting of free-radical and non-radical pathways

As a typical “One Health” issue, antibiotic resistance has been considered as a worldwide threat to public health. And its spread can be restricted by antibiotics degradation, inactivation of antibiotic resistant bacteria (ARB), and removal of antibiotic resistance genes (ARGs). In this study, iron-cobalt bimetallic biochar (Fe-Co@BC) activated peroxymonosulfate (PMS) system was applied to degrade ampicillin (AMP), inactivate ARB (E. coli DH5α), and remove ARGs (plasmid-encoded blaTEM-1). AMP was degraded efficiently (about 99 %) in the Fe-Co@BC/PMS system within 40 min, and the catalyst still showed good stability after four cycles. Similarly, the Fe-Co@BC/PMS system achieved complete inactivation of ARB (about 107 CFU/mL) within 5 min, and the oxidative damages of ARB were further verified in terms of cell viability, cell membrane integrity, and enzyme activity. The removal efficiency of blaTEM-1 was 3.47 log within 60 min, and the catalyst dose, PMS concentration, initial ARB concentration, pH, and inorganic anions had significant effects on blaTEM-1 removal. The coexistence of non-radical (1O2, electron transfer) and free-radical (SO4−, O2−, and OH) pathways in the Fe-Co@BC/PMS system was demonstrated by electron paramagnetic resonance techniques and free radical quenching experiments, with SO4− and 1O2 being the main reactive species. XPS results showed that redox cycles between Co (III)/Co (II) and Fe (III)/Fe (II) were important to the efficient catalytic performance of Fe-Co@BC. Moreover, possible degradation pathway of AMP was proposed according to LC-MS results and density functional theory analysis. The results obtained in this study provide a novel sight on preventing the propagation of antibiotic resistance in aquatic settings.

Removal of antibiotic resistant bacteria in wastewater treatment plants

Antibiotic Resistant Bacteria (ARB) emergence is an increasing threat to public health globally. Wastewater Treatment Plants (WWTPs) play a crucial role in the dissemination of ARB in the environment due to limitations in ARB removal. This study investigated the presence and characteristics of ARB, specifically Extended-Spectrum Beta-Lactamase producing Escherichia coli (ESBL-Ec) and Vancomycin Resistant Enterococci (VRE) , in two WWTPs treating wastewater from hospital and domestic source. The study employed phenotypic and genotypic tests to confirm the presence of ESBL-Ec and VRE, and evaluated their resistance to antibiotics. The results indicated the presence of ESBL-Ec and VRE in both WWTP influent up to (6.0 ± 0.25) x 105 and (1.38 ± 0.25) × 104 CFU/100 mL, respectively, suggesting the potential dissemination of ARB to environment. Although the WWTPs demonstrated relatively high removal efficiencies for ESBL-Ec and VRE up to 4.1 and 5.0 log reduction, respectively, the presence of resistant genes suggested the need for further optimization of treatment processes to mitigate the spread of ARB. The findings highlighted the significance of improved disinfection methods, monitoring antibiotic usage, and implementing robust antimicrobial resistance surveillance systems in WWTPs to minimize the environmental impact associated with ARB dissemination.

Investigating antimicrobial resistance determinants and micropollutants in urban sewage treatment plants of India: Occurrence, removal and ecotoxicological risk

Environmental contamination caused by emerging pollutants (EPs) and their associated ecological risk have received limited attention in India. Thus, this study aims to address this gap by investigating the occurrence and removal of antibiotic resistant bacteria (ARB), antibiotic resistance genes (ARGs) and pharmaceutical and personal care products (PPCPs) in two sewage treatment plants (STPs) in New Delhi. The study also assessed the ecological risk associated with PPCPs in aquatic environments. Among the targeted ARB and ARGs, erythromycin resistant bacteria and ermB gene, respectively were the most ubiquitous pollutants in the influent of both STPs. In the final effluent, there was a reduction ranging from 0.8 log to 2.8 log units for most ARB, while removal of the majority of ARGs was less than 1 log unit. The secondary treatment demonstrated better removal of total ARG concentrations compared to the tertiary treatment methods employed in both STPs. Regarding PPCPs, metformin was quantified in both influent and effluent samples at a concentration exceeding 19,000 ng/L, indicating its persistence in wastewater. High concentrations of ARB, ARGs, and PPCPs were observed in undigested biosolids, while low to moderate removal of these pollutants was observed after anaerobic digestion. To assess the ecological risk, a risk quotient (RQ) assessment was conducted. The results revealed that compounds such as erythromycin, terbinafine, 17-α ethinylestradiol (EE2), 17-β estradiol (E2), diclofenac, triclosan, carbamazepine, and mefenamic acid exhibited high risks in the effluent. Additionally, EE2 and E2 showed higher risk levels in the digested biosolids, indicating potential risks to the aquatic ecosystem.

Removal of antibiotic-resistant bacteria and genes by Solar-activated Ferrate/ Peroxymonosulfate: Efficiency in aquaculture wastewater and mechanism

Removal of antibiotic-resistant bacteria and genes by Solar-activated Ferrate/ Peroxymonosulfate: Efficiency in aquaculture wastewater and mechanism

The removal of antibiotic resistant bacteria and antibiotic resistance genes by sulfidated nanoscale zero-valent iron activating periodate: Efficacy and mechanism

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) have drawn much more attention due to their high risk on human health and ecosystem. In this study, the performance of sulfidated nanoscale zero-valent iron (S-nZVI)/periodate (PI) system toward ARB inactivation and ARGs removal was systematically investigated. The S-nZVI/PI system could realize the complete inactivation of 1 × 108 CFU/mL kanamycin, ampicillin, and tetracycline-resistant E. coli HB101 within 40 min, meanwhile, possessed the ability to remove the intracellular ARGs (iARGs) (including aphA, tetA, and tnpA) carried by E. coli HB101. Specifically, the removal of aphA, tetA, and tnpA by S-nZVI/PI system after 40 min reaction was 0.31, 0.47, and 0.39 log10copies/mL, respectively. The reactive species attributed to the E. coli HB101 inactivation were HO• and O2•−, which could cause the destruction of E. coli HB101 morphology and enzyme system (such as superoxide dismutase and catalase), the loss of intracellular substances, and the damage of iARGs. Moreover, the influence of the dosage of PI and S-nZVI, the initial concentration of E. coli HB101, as well as the co-existing substance (such as HCO3−, NO3−, and humic acid (HA)) on the inactivation of E. coli HB101 and its corresponding iARGs removal was also conducted. It was found that the high dosage of PI and S-nZVI and the low concentration of E. coli HB101 could enhance the disinfection performance of S-nZVI/PI system. The presence of HCO3−, NO3−, and HA in S-nZVI/PI system showed inhibiting role on the inactivation of E. coli HB101 and its corresponding iARGs removal. Overall, this study demonstrates the superiority of S-nZVI/PI system toward ARB inactivation and ARGs removal.

The Fate and Occurrence of Antibiotic-Resistant Bacteria and Antibiotic Resistance Genes during Advanced Wastewater Treatment and Disinfection: A Review

Antimicrobial resistance (AMR) is a serious problem for modern society, not only associated with clinical environments, but also the natural environment. Conventional wastewater treatment plants (WWTPs) are important nodes for the dissemination of antibiotic resistance to the aquatic environment since they are reservoirs of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and antibiotic residues. WWTPs are not designed to remove these antibiotic resistance determinants from wastewater, and as a result, they are present in treated effluent, leading to environmental and public health concerns regarding wastewater disposal and reuse. Additional treatments combined with conventional WWTPs can be barriers to the spread of AMR to the environment. In order to understand the effect of wastewater treatment methods on the removal of ARB and ARGs, an extensive bibliographic study was conducted. This review summarizes the efficiency of conventional disinfection methods, tertiary wastewater treatment, and advanced oxidation processes (AOPs) to remove ARB and ARGs from wastewater. In the context of the revised Urban Wastewater Treatment Directive 91/271/EEC, further studies are needed on the removal potential of AOPs on a full-scale, as they offer great potential for the removal of ARB and ARGs with a low formation of toxic by-products compared to conventional disinfection methods.

Microbiome and Resistome Profiles along a Sewage-Effluent-Reservoir Trajectory Underline the Role of Natural Attenuation in Wastewater Stabilization Reservoirs.

Antibiotic-resistant bacteria and antibiotic resistance gene (ARGs) loads dissipate through sewage treatment plants to receiving aquatic environments, but the mechanisms that mitigate the spread of these ARGs are not well understood due to the complexity of full-scale systems and the difficulty of source tracking in downstream environments. To overcome this problem, we targeted a controlled experimental system comprising a semicommercial membrane-aerated bioreactor (MABR), whose effluents fed a 4,500-L polypropylene basin that mimicked effluent stabilization reservoirs and receiving aquatic ecosystems. We analyzed a large set of physicochemical measurements, concomitant with the cultivation of total and cefotaxime-resistant Escherichia coli, microbial community analyses, and quantitative PCR (qPCR)/digital droplet PCR (ddPCR) quantification of selected ARGs and mobile genetic elements (MGEs). The MABR removed most of the sewage-derived organic carbon and nitrogen, and simultaneously, E. coli, ARG, and MGE levels dropped by approximately 1.5- and 1.0-log unit mL-1, respectively. Similar levels of E. coli, ARGs, and MGEs were removed in the reservoir, but interestingly, unlike in the MABR, the relative abundance (normalized to 16S rRNA gene-inferred total bacterial abundance) of these genes also decreased. Microbial community analyses revealed the substantial shifts in bacterial and eukaryotic community composition in the reservoir relative to the MABR. Collectively, our observations lead us to conclude that the removal of ARGs in the MABR is mainly a consequence of treatment-facilitated biomass removal, whereas in the stabilization reservoir, mitigation is linked to natural attenuation associated with ecosystem functioning, which includes abiotic parameters, and the development of native microbiomes that prevent the establishment of wastewater-derived bacteria and associated ARGs. IMPORTANCE Wastewater treatment plants are sources of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), which can contaminate receiving aquatic environments and contribute to antibiotic resistance. We focused on a controlled experimental system comprising a semicommercial membrane-aerated bioreactor (MABR) that treated raw sewage, whose effluents fed a 4,500-L polypropylene basin that mimicked effluent stabilization reservoirs. We evaluated ARB and ARG dynamics across the raw-sewage-MABR-effluent trajectory, concomitant with evaluation of microbial community composition and physicochemical parameters, in an attempt to identify mechanisms associated with ARB and ARG dissipation. We found that removal of ARB and ARGs in the MABR was primarily associated with bacterial death or sludge removal, whereas in the reservoir it was attributed to the inability of ARBs and associated ARGs to colonize the reservoir due to a dynamic and persistent microbial community. The study demonstrates the importance of ecosystem functioning in removing microbial contaminants from wastewater.

Efficient photo-Fenton reaction for tetracycline and antibiotic resistant bacteria removal using hollow Fe-doped In2O3 nanotubes: From theoretical research to practical application

The low exposure of active sites and the slow electron transfer rate still restrict the wide application of the photo-Fenton system of Fe-based photocatalyst in practical water treatment. Herein, we prepared a hollow Fe-doped In2O3 nanotube (h-Fe-In2O3) catalyst for activating hydrogen peroxide (H2O2) to remove tetracycline (TC) and antibiotic resistant bacteria (ARB). Incorporation of Fe could shorten the band gap and increase the absorption capacity of visible light. Meanwhile, the increase of electron density at the Fermi level promotes the interfacial electron transport. The large specific surface area of the tubular structure exposes more Fe active site and the Fe-O-In site reduces the energy barrier of H2O2 activation, resulting in more and faster formation of hydroxyl radicals (•OH). After continuous operation for 600 min, the h-Fe-In2O3 reactor still can remove 85% TC and about 3.5 log ARB in secondary effluent, showing good stability and durability for practical wastewater treatment.

Multiple Antibiotic-Resistant Bacteria Resistant to Electrochemical Disinfection with Variation of Key Antibiotic Resistance Genes

Electrochemical disinfection (ED) is effective in removal of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) during wastewater treatment. However, the inner relationship of antibiotic-resistant phenotypes with their genotypes of ARB is still unclear in the ED process. This study explored the disinfection mechanism at the microcosmic level using four Escherichia coli (E. coli) strains with different antibiotic-resistant phenotypes. Results showed that bacteria with multiple antibiotic resistance tended to have stronger viability in disinfection compared with those resistant to fewer antibiotics. Interestingly, antibiotic-resistant phenotypes changed little in the disinfection process, while genotypes closely responded to bacterial resistance of different E. coli. In detail, beta-lactamase resistance genes played a leading role in the cross-resistance between antibiotics and electrochemical oxidation. They were proved to reduce oxidative destruction by increasing the strength of the cell wall and membrane. In addition, diaminopyrimidine and macrolide-lincosamide-streptogramin B resistance genes are also closely related to the bacterial resistance to ED. Combined with the quantitative determination of ARGs, the abundance of IntI1 and aminoglycoside resistance genes can be regarded as indicators for the risk of cross-resistance to antibiotics and electrochemical oxidation. This study provided important references for in depth understanding and accurate control of antibiotic resistance with advanced oxidation processes.

Removal of antibiotic resistant bacteria in wastewater by aggregation-induced emission photosensitizer

The spread of antibiotic resistant bacteria from wastewater to the environment will pose serious threats to human health. It is a potential solution to prepare photosensitizers with broad-spectrum antibacterial activity for use in the photo-oxidation process to supplement the wastewater treatment system. Here, an aggregation-induced emission photosensitizer with D-π-A structure (TBTPy) has been reasonably designed and successfully developed. TBTPy can generate singlet oxygen with extraordinarily high efficiency under white-light irradiation owing to the small singlet–triplet energy gap. TBTPy has a rapid and efficient photo-oxidative killing effect on bacteria and fungi (such as MRSA, S. aureus, E. coli and C. albicans). TBTPy kills bacteria by binding to bacterial surface and releasing singlet oxygen to destroy cell membrane, leading to leakage of bacterial genetic material. This successful case can provide practical guidance for the subsequent development of AIE photosensitizers.

Removal of antibiotic resistant bacteria and genes by nanoscale zero-valent iron activated persulfate: Implication for the contribution of pH decrease

The mechanism of removing antibiotic resistant bacteria (ARB) and antibiotic resistant genes (ARGs) by persulfate was attributed to the generation of reactive oxygen species (ROS). However, the potential contribution of decreased pH in persulfate system to ARB and ARGs removal has rarely been reported. Here, the efficiency and mechanism of removing ARB and ARGs by nanoscale zero-valent iron activated persulfate (nZVI/PS) were investigated. Results showed that the ARB (2 × 108 CFU/mL) could be completely inactivated within 5 min, and the removal efficiencies of sul1 and intI1 were 98.95% and 99.64% by nZVI/20 mM PS, respectively. Investigation of mechanism revealed that hydroxyl radicals was the dominant ROS of nZVI/PS in removing ARB and ARGs. Importantly, the pH of nZVI/PS system was greatly decreased, even to 2.9 in nZVI/20 mM PS system. Impressively, when the pH of the bacterial suspension was adjusted to 2.9, the removal efficiency of ARB, sul1 and intI1 were 60.33%, 73.76% and 71.51% within 30 min, respectively. Further excitation-emission-matrix analysis confirmed that decreased pH contributed to ARB damage. The above results on the effect of pH indicated that the decreased pH of nZVI/PS system also made an important contribution for the removal of ARB and ARGs.

Stormwater runoff treatment through electrocoagulation: antibiotic resistant bacteria removal and its transmission risks

ABSTRACT Recently, increasing attention has been paid to antibiotic resistant bacteria (ARB) in stormwater runoff. However, there were little data on ARB removal through electrocoagulation (EC) treatment. In this study, batch experiments were conducted to investigate key designs for ARB removal, role of SS, effects of water matrix, and potential risks after EC treatment under the pre-determined conditions. EC treatment with 5 mA/cm2 of current density and 4 cm of inter-electrode distance was optimal with the highest ARB removal (3.04 log reduction for 30 min). The presence of SS significantly improved ARB removal during EC treatment, where ARB removal increased with the increase of SS levels when SS less than 300 mg/L. Large ARB removal was found under particles with size lower than 150 μm with low contribution (less than 10%) of the settlement without EC treatment, implying that the enhancement of ARB adsorption onto small particles could be one of the reasonable approaches for ARB removal through EC treatment. ARB removal increased firstly and then decreased with the increase of pH, while had proportional relationship with conductivity. After the optimal condition, there were weak conjugation transfer but high transformation frequency (5.5 × 10−2 for bla TEM) for target antibiotic resistance genes (ARGs), indicating that there could be still a risk of antibiotic resistance transformation after EC treatment. These suggested that the combination of EC and other technologies (like electrochemical disinfection) should be potential ways to control antibiotic resistance transmission through stormwater runoff.

Removal of antibiotic resistant bacteria and genes by post-pyrolysis bio-hybridcarbon/peroxymonosulfate system: Gene-degrading intermediates of bioinformatic identification based on corrected-nanopore sequencing and preference mechanism

Antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) have been recognized as emerging pollutants. It is accessible to restrict disseminating antibiotic resistance by inactivating ARB and degrading its ARGs by oxidation treatment processes in aquatic environment, but until now the producing gene-degrading intermediates are not reported. In this study, a novel post-pyrolysis bio-hybridcarbon (Co@PS-BC) was prepared for peroxymonosulfate (PMS) activation to eliminate both E. coli DH5α-based ARB and its ARGs (blaTEM-1 and NPTII). Importantly, gene-degradation intermediates of ARGs were analyzed by Nanopore sequencing and Illumina sequencing. The results of bioinformatic analyses showed that the gene-degrading intermediates held the abundant GGC motifs, relatively high GC content and base preference of breakpoints toward guanine. Overall, our work develops a novel approach for effectively eliminating ARB and ARGs from water, and provides an insight into the composition and base preference of gene-degrading intermediates.

Removal of antibiotic resistant bacteria and plasmid-encoded antibiotic resistance genes in water by ozonation and electro-peroxone process

The electro-peroxone (EP) process is an electricity-based oxidation process enabled by electrochemically generating hydrogen peroxide (H2O2) from cathodic oxygen (O2) reduction during ozonation. In this study, the removal of antibiotic resistant bacteria (ARB) and plasmid-encoded antibiotic resistance genes (ARGs) during groundwater treatment by ozonation alone and the EP process was compared. Owing to the H2O2-promoted ozone (O3) conversion to hydroxyl radicals (•OH), higher •OH exposures, but lower O3 exposures were obtained during the EP process than ozonation alone. This opposite change of O3 and •OH exposures decreases the efficiency of ARB inactivation and ARG degradation moderately during the EP process compared with ozonation alone. These results suggest that regarding ARB inactivation and ARG degradation, the reduction of O3 exposures may not be fully counterbalanced by the rise of •OH exposures when changing ozonation to the EP process. However, due to the rise of •OH exposure, plasmid DNA was more effectively cleaved to shorter fragments during the EP process than ozonation alone, which may decrease the risks of natural transformation of ARGs. These findings highlight that the influence of the EP process on ARB and ARG inactivation needs to be considered when implementing this process in water treatment.