Antiepileptic drug carbamazepine promotes horizontal transfer of plasmid-borne multi-antibiotic resistance genes within and across bacterial genera

How micro-/nano-plastics influence the horizontal transfer of antibiotic resistance genes - A review

Plastic debris such as microplastics (MPs) and nanoplastics (NPTs), along with antibiotic resistance genes (ARGs), are pervasive in the environment and are recognized as significant global health and ecological concerns. Micro-/nano-plastics (MNPs) have been demonstrated to favor the spread of ARGs by enhancing the frequency of horizontal gene transfer (HGT) through various pathways. This paper comprehensively and systematically reviews the current study with focus on the influence of plastics on the HGT of ARGs. The critical role of MNPs in the HGT of ARGs has been well illustrated in sewage sludge, livestock farms, constructed wetlands and landfill leachate. A summary of the performed HGT assay and the underlying mechanism of plastic-mediated transfer of ARGs is presented in the paper. MNPs could facilitate or inhibit HGT of ARGs, and their effects depend on the type, size, and concentration. This review provides a comprehensive insight into the effects of MNPs on the HGT of ARGs, and offers suggestions for further study. Further research should attempt to develop a standard HGT assay and focus on investigating the impact of different plastics, including the oligomers they released, under real environmental conditions on the HGT of ARGs.

The effects of methylparaben exposure on biofilm tolerance to chlorine disinfection

Parabens are emerging contaminants that have been detected in drinking water. Their presence in DW distribution systems (DWDS) can alter bacterial behaviour, characteristics, and structure, which may compromise DW disinfection. This work provides insights into the impact of methylparaben (MP) on the tolerance to chlorine disinfection and antibiotics from dual-species biofilms formed by Acinetobacter calcoaceticus and Stenotrophomonas maltophilia isolated from DW and grown on high-density polyethylene (HDPE) and polypropylene (PPL). Results showed that dual-species biofilms grown on PPL were more tolerant to chlorine disinfection, expressing a decrease of over 50 % in logarithmic reduction values of culturable cells in relation to non-exposed biofilms. However, bacterial tolerance to antibiotics was not affected by MP presence. Although MP-exposed dual-species biofilms grown on HDPE and PPL were metabolically more active than non-exposed counterparts, HDPE seems to be the material with lower impact on DW risk management and disinfection, if MP is present. Overall, results suggest that MP presence in DW may compromise chlorine disinfection, and consequently affect DW quality and stability, raising potential public health issues.

The mechanism differences between sulfadiazine degradation and antibiotic resistant bacteria inactivation by iron-based graphitic biochar and peroxydisulfate system

In this study, the activation of peroxydisulfate (PS) by K2FeO4-activation biochar (KFeB) and acid-picking K2FeO4-activation biochar (AKFeB) was investigated to reveal the mechanism differences between iron site and graphitic structure in sulfadiazine (SDZ) degradation and ARB inactivation, respectively. KFeB/PS and AKFeB/PS systems had similar degradation property towards SDZ, but only KFeB/PS system showed excellent bactericidal property. The mechanism study demonstrated that dissolved SDZ was degraded through electron transfer pathway mediated by graphitic structure, while suspended ARB was inactivated through free radicals generated by iron-activated PS, accompanied by excellent removal on antibiotic resistance genes (ARGs). The significant decrease in conjugative transfer frequency indicated the reduced horizontal gene transfer risk of ARGs after treatment with KFeB/PS system. Transcriptome data suggested that membrane protein channel disruption and adenosine triphosphate synthesis inhibition were key reasons for conjugative transfer frequency reduction. Continuous flow reactor of KFeB/PS system can efficiently remove antibiotics and ARB, implying the potential application in practical wastewater purification. In conclusion, this study provides novel insights for classified and collaborative control of antibiotics and ARB by carbon-based catalysts driven persulfate advanced oxidation technology.

Dissemination and persistence of antimicrobial resistance (AMR) along the wastewater-river continuum

Antimicrobial resistance (AMR) is a global health hazard. Although clinical and agricultural environments are well-established contributors to the evolution and dissemination of AMR, research on wastewater treatment works (WwTWs) has highlighted their potential role as disseminators of AMR in freshwater environments. Using metagenomic sequencing and analysis, we investigated the changes in resistomes and associated mobile genetic elements within untreated wastewater influents and treated effluents of five WwTWs, and sediments collected from corresponding river environments in Oxfordshire, UK, across three seasonal periods within a year. Our analysis demonstrated a high diversity and abundance of antimicrobial resistance genes (ARGs) in untreated wastewater influents, reflecting the varied anthropogenic and environmental origins of wastewater. WwTWs effectively reduced AMR in the final effluent, with an average 87 % reduction in normalised ARG abundance and an average 63 % reduction in richness. However, wastewater effluents significantly impacted the antimicrobial resistome of the receiving rivers, with an average 543 % increase in ARG abundance and a 164 % increase in richness from upstream sediments to downstream sediments. The normalised abundance of the human gut-associated bacteriophage crAssphage was highly associated with both ARG abundance and richness. We observed seasonal variation in the resistome of raw influent which was not found in the effluent-receiving sediments. We illustrate the potential of WwTWs as focal points for disseminating ARGs and resistance-selecting chemicals, contributing to the elevation of environmental AMR. Our study emphasises the need for a comprehensive understanding of the anthropogenic impacts on AMR evolution and dissemination in wastewater and river environments, informing efforts to mitigate this growing public health crisis.

Beta-blocker drives the conjugative transfer of multidrug resistance genes in pure and complex biological systems

Drug resistance poses a high risk to human health. Extensive use of non-antibiotic drugs contributes to antibiotic resistance genes (ARGs) transfer. However, how they affect the spread of broad-host plasmids in complex biological systems remains unknown. This study investigated the effect of metoprolol on the transfer frequency and host range of ARGs in both intrageneric and intergeneric pure culture systems, as well as in anammox microbiome. The results showed that environmental concentrations of metoprolol significantly promoted the intrageneric and intergeneric conjugative transfer. Initially, metoprolol induced excessive oxidative stress, resulting in high cell membrane permeability and bacterial SOS response. Meanwhile, more pili formation increased the adhesion and contact between bacteria, and the abundance of conjugation-related genes also increased significantly. Activation of the electron transport chain provided more ATP for this energy-consuming process. The underlying mechanism was further verified in the complex anammox conjugative system. Metoprolol induced the enrichment of ARGs and mobile genetic elements. The enhanced bacterial interaction and energy generation facilitated the high conjugative transfer frequency of ARGs. In addition, plasmid-borne ARGs tended to transfer to opportunistic pathogens. This work raises public concerns about the health and ecological risks of non-antibiotic drugs.

Impact of chlorine disinfection on intracellular and extracellular antimicrobial resistance genes in wastewater treatment and water reclamation

Wastewater treatment plants and water reclamation facilities are reservoirs of antimicrobial resistance genes (ARGs). These ARGs are not limited solely to intracellular DNA (inARGs) but include extracellular DNA (exARGs) present in wastewater. The release of exARGs from cells can be exacerbated by treatment processes, including chlorine disinfection, which disrupts bacterial cells. Given the potential for exARGs to drive horizontal gene transfer and contribute to the proliferation of antimicrobial resistance, it is imperative to recognize these fractions as emerging environmental pollutants. In this study, we conducted a comprehensive year-long assessment of both inARGs and exARGs, further differentiating between dissolved exARGs (Dis_exARGs) and exARGs adsorbed onto particulate matter (Ads_exARGs), within a full-scale wastewater treatment and water reclamation facility. The results revealed that Ads_exARGs comprised up to 30 % of the total ARGs in raw sewage with high biomass content. Generally, treatments at low and high doses of chlorine increased the abundance of Dis_exARGs and Ads_exARGs. The fate of ARG levels that varied depending on the type of ARGs suggested variations in the susceptibility of the host bacteria to chlorination. Moreover, co-occurrence of several potential opportunistic pathogenic bacteria and ARGs were observed. Therefore, we propose higher doses of chlorination as a prerequisite for the effective removal of inARGs and exARGs.

Mechanisms of conjugative transfer of antibiotic resistance genes induced by extracellular polymeric substances: Insights into molecular diversities and electron transfer properties

Dissemination of antibiotic resistance genes (ARGs) has become a critical threat to public health. Activated sludge, rich in extracellular polymeric substances (EPS), is an important pool of ARGs. In this study, mechanisms of conjugation transfer of ARGs induced by EPS, including tightly bound EPS (TBEPS), soluble EPS (SEPS), and loosely bound EPS (LBEPS), were explored in terms of molecular diversities and electron transfer properties of EPS. Conjugation transfer frequency was increased by 9.98-folds (SEPS), 4.21-folds (LBEPS), and 15.75-folds (TBEPS) versus the control, respectively. Conjugation-related core genes involving SOS responses (9 genes), membrane permeability (18 genes), intercellular contact (17 genes), and energy metabolism pathways (13 genes) were all upregulated, especially in the presence of TBEPS. Carbohydrates and aliphatic substances in SEPS and LBEPS were contributors to ARG transfer, via influencing reactive oxygen species (ROS) formation (SEPS) and ROS and adenosine triphosphate (ATP) production (LBEPS). TBEPS had the highest redox potential and greatest lability and facilitated electron transfer and alternated respiration between cells, thus promoting ARG transfer by producing ATP. Generally, the chemical molecular characteristics and redox properties of EPS facilitated ARG transfer mainly by influencing lipid peroxidation and ATP, respectively.

Pheromone cCF10 inhibits the antibiotic persistence of Enterococcus faecalis by modulating energy metabolism

Introduction

Bacterial resistance presents a major challenge to both the ecological environment and human well-being, with persistence playing a key role. Multiple studies were recently undertaken to examine the factors influencing the formation of persisters and the underlying process, with a primary focus on Gram-negative bacteria and Staphylococcus aureus (Gram-positive bacteria). Enterococcus faecalis (E. faecalis) is capable of causing a variety of infectious diseases, but there have been few studies of E. faecalis persisters. Previous studies have shown that the sex pheromone cCF10 secreted by E. faecalis induces conjugative plasmid transfer. However, whether the pheromone cCF10 regulates the persistence of E. faecalis has not been investigated.

Methods

As a result, we investigated the effect and potential molecular mechanism of pheromone cCF10 in regulating the formation of persisters in E. faecalis OG1RF using a persistent bacteria model.

Results and discussion

The metabolically active E. faecalis OG1RF reached a persistence state and temporarily tolerated lethal antibiotic concentrations after 8  h of levofloxacin hydrochloride (20 mg/mL) exposure, exhibiting a persistence rate of 0.109 %. During the growth of E. faecalis OG1RF, biofilm formation was a critical factor contributing to antibiotic persistence, whereas 10 ng/mL cCF10 blocked persister cell formation. Notably, cCF10 mediated the antibiotic persistence of E. faecalis OG1RF via regulating metabolic activity rather than suppressing biofilm formation. The addition of cCF10 stimulated the Opp system and entered bacterial cells, inhibiting (p)ppGpp accumulation, thus maintaining the metabolically active state of bacteria and reducing persister cell generation. These findings offer valuable insights into the formation, as well as the control mechanism of E. faecalis persisters.

Critical insights into the Hormesis of antibiotic resistome in saline soil: Implications from salinity regulation

Soil is recognized as an important reservoir of antibiotic resistance genes (ARGs). However, the effect of salinity on the antibiotic resistome in saline soils remains largely misunderstood. In this study, high-throughput qPCR was used to investigate the impact of low-variable salinity levels on the occurrence, health risks, driving factors, and assembly processes of the antibiotic resistome. The results revealed 206 subtype ARGs across 10 categories, with medium-salinity soil exhibiting the highest abundance and number of ARGs. Among them, high-risk ARGs were enriched in medium-salinity soil. Further exploration showed that bacterial interaction favored the proliferation of ARGs. Meanwhile, functional genes related to reactive oxygen species production, membrane permeability, and adenosine triphosphate synthesis were upregulated by 6.9%, 2.9%, and 18.0%, respectively, at medium salinity compared to those at low salinity. With increasing salinity, the driver of ARGs in saline soils shifts from bacterial community to mobile gene elements, and energy supply contributed 28.2% to the ARGs at extreme salinity. As indicated by the neutral community model, stochastic processes shaped the assembly of ARGs communities in saline soils. This work emphasizes the importance of salinity on antibiotic resistome, and provides advanced insights into the fate and dissemination of ARGs in saline soils.

Occurrence and dissemination of antibiotics and antibiotic resistance in aquatic environment and its ecological implications: a review

The occurrence of antibiotics and antibiotic-resistant bacteria (ARBs), genes (ARGs), and mobile genetic elements (MGEs) in aquatic systems is growing global public health concern. These emerging micropollutants, stemming from improper wastewater treatment and disposal, highlight the complex and evolving nature of environmental pollution. Current literature reveals potential biases, such as a geographical focus on specific regions, leading to an insufficient understanding of the global distribution and dynamics of antibiotic resistance in aquatic systems. There is methodological inconsistency across studies, making it challenging to compare findings. Potential biases include sample collection inconsistencies, detection sensitivity variances, and data interpretation variability. Gaps in understanding include the need for comprehensive, standardized long-term monitoring programs, elucidating the environmental fate and transformation of antibiotics and resistance genes. This review summarizes current knowledge on the occurrence and dissemination of emerging micropollutants, their ecological impacts, and the global health implications of antimicrobial resistance. It highlights the need for interdisciplinary collaborations among researchers, policymakers, and stakeholders to address the challenges posed by antibiotic resistance in aquatic resistance in aquatic systems effectively. This review highlights widespread antibiotic and antibiotic resistance in aquatic environment, driven by human and agricultural activities. It underscores the ecological consequences, including disrupted microbial communities and altered ecosystem functions. The findings call for urgent measures to mitigate antibiotics pollution and manage antibiotic resistance spread in water bodies.

Characterization of Escherichia coli pathogenicity and drug resistance in yolk peritonitis

Yolk Peritonitis can lead to a rapid decline in egg production, which seriously affects the health of laying hens and the profitability of chicken farms. Escherichia coli (E. coli) is the most common cause of yolk peritonitis in laying hens. In this study, bacterial samples were collected from the ovaries and fallopian tubes of laying hens with suspected yolk peritonitis from a laying farm in Jiangsu Province, and their pathogenicity and drug resistance were investigated. Initially, morphological and biochemical detection methods were employed to isolate and identify the pathogenic bacteria. The results showed that a total of 16 strains of E. coli were isolated from laying hens with yolk peritonitis. Subsequently, the drug resistance and pathogenicity of a randomly selected E. coli strain were analyzed and predicted by genome sequencing technology, and the drug resistance of E. coli was verified by drug sensitivity test and PCR. Finally, the virulence was verified by infection experiment in mice. The study revealed that the egg-yolk peritonitis in laying hens was caused by E. coli infection, and the genome sequencing analysis revealed that the bacteria had multidrug resistance and high virulence. The drug susceptibility testing indicates that E. coli exhibited resistance to aminoglycosides, β-lactam, macrolides, fluoroquinolones, and sulfonamides. In this study, resistance genes including KdpE, aadA5, APH(3 ")-ID, APH(6)-ID, and TEM-1 were identified, and their expression levels varied across different stages of bacterial growth. The results of virulence analysis indicated a mortality rate of 50% in mice infected with E. coli at a concentration of 2.985 × 107 CFU/mL. E. coli infection resulted in damage to various tissues and organs in mice, with the intestinal tissue structure being the most severely affected. This study provides a reference for the study of drug resistance mechanisms in E. coli and provides valuable insights into the selection of drugs for the treatment of vitelline peritonitis.

Emerging contaminants: A One Health perspective

Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary health. Despite global efforts to mitigate legacy pollutants, the continuous introduction of new substances remains a major threat to both people and the planet. In response, global initiatives are focusing on risk assessment and regulation of emerging contaminants, as demonstrated by the ongoing efforts to establish the UN's Intergovernmental Science-Policy Panel on Chemicals, Waste, and Pollution Prevention. This review identifies the sources and impacts of emerging contaminants on planetary health, emphasizing the importance of adopting a One Health approach. Strategies for monitoring and addressing these pollutants are discussed, underscoring the need for robust and socially equitable environmental policies at both regional and international levels. Urgent actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.

Quaternary ammonium biocides promote conjugative transfer of antibiotic resistance gene in structure- and species-dependent manner

The linkage between biocides and antibiotic resistance has been widely suggested in laboratories and various environments. However, the action mechanism of biocides on antibiotic resistance genes (ARGs) spread is still unclear. Thus, 6 quaternary ammonium biocides (QACs) with different bonded substituents or alkyl chain lengths were selected to assess their effects on the conjugation transfer of ARGs in this study. Two conjugation models with the same donor (E. coli DH5α (RP4)) into two receptors, E. coli MG1655 and pathogenic S. sonnei SE6-1, were constructed. All QACs were found to significantly promote intra- and inter-genus conjugative transfer of ARGs, and the frequency was highly impacted by their structure and receptors. At the same environmental exposure level (4 × 10-1 mg/L), didecyl dimethyl ammonium chloride (DDAC (C10)) promoted the most frequency of conjugative transfer, while benzathine chloride (BEC) promoted the least. With the same donor, the enhanced frequency of QACs of intra-transfer is higher than inter-transfer. Then, the acquisition mechanisms of two receptors were further determined using biochemical combined with transcriptome analysis. For the recipient E. coli, the promotion of the intragenus conjugative transfer may be associated with increased cell membrane permeability, reactive oxygen species (ROS) production and proton motive force (PMF)-induced enhancement of flagellar motility. Whereas, the increase of cell membrane permeability and decreased flagellar motility due to PMF disruption but encouraged biofilm formation, maybe the main reasons for promoting intergenus conjugative transfer in the recipient S. sonnei. As one pathogenic bacterium, S. sonnei was first found to acquire ARGs by biocide exposure.

Influence of selected non-antibiotic pharmaceuticals on antibiotic resistance gene transfer in Escherichia coli

BACKGROUND

Antibiotic resistance genes (ARGs) transfer rapidly among bacterial species all over the world contributing to the aggravation of antibiotic resistance crisis. Antibiotics at sub-inhibitory concentration induce horizontal gene transfer (HRT) between bacteria, especially through conjugation. The role of common non-antibiotic pharmaceuticals in the market in disseminating antibiotic resistance is not well studied.

OBJECTIVES

In this work, we indicated the effect of some commonly used non-antibiotic pharmaceuticals including antiemetic (metoclopramide HCl) and antispasmodics (hyoscine butyl bromide and tiemonium methyl sulfate) on the plasmid-mediated conjugal transfer of antibiotic resistance genes between pathogenic E. coli in the gastric intestinal tract (GIT).

METHODS

Broth microdilution assay was used to test the antibacterial activity of the tested non-antibiotic pharmaceuticals. A conjugation mating system was applied in presence of the studied non-antibiotic pharmaceuticals to test their effect on conjugal transfer frequency. Plasmid extraction and PCR were performed to confirm the conjugation process. Transmission electron microscopy (TEM) was used for imaging the effect of non-antibiotic pharmaceuticals on bacterial cells.

RESULTS

No antibacterial activity was reported for the used non-antibiotic pharmaceuticals. Plasmid-mediated conjugal transfer between isolates was induced by metoclopramide HCl but suppressed by hyoscine butyl bromide. Tiemonium methylsulfate slightly promoted conjugal transfer. Aggregation between cells and periplasmic bridges was clear in the case of metoclopramide HCl while in presence of hyoscine butyl bromide little affinity was observed.

CONCLUSION

This study indicates the contribution of non-antibiotic pharmaceuticals to the dissemination and evolution of antibiotic resistance at the community level. Metoclopramide HCl showed an important role in the spread of antibiotic resistance.

Non-Canonical Aspects of Antibiotics and Antibiotic Resistance

The understanding of antibiotic resistance, one of the major health threats of our time, is mostly based on dated and incomplete notions, especially in clinical contexts. The "canonical" mechanisms of action and pharmacodynamics of antibiotics, as well as the methods used to assess their activity upon bacteria, have not changed in decades; the same applies to the definition, acquisition, selective pressures, and drivers of resistance. As a consequence, the strategies to improve antibiotic usage and overcome resistance have ultimately failed. This review gathers most of the "non-canonical" notions on antibiotics and resistance: from the alternative mechanisms of action of antibiotics and the limitations of susceptibility testing to the wide variety of selective pressures, lateral gene transfer mechanisms, ubiquity, and societal factors maintaining resistance. Only by having a "big picture" view of the problem can adequate strategies to harness resistance be devised. These strategies must be global, addressing the many aspects that drive the increasing prevalence of resistant bacteria aside from the clinical use of antibiotics.

EDTA enables to alleviate impacts of metal ions on conjugative transfer of antibiotic resistance genes

Various heavy metals are reported to be able to accelerate horizontal transfer of antibiotic resistance genes (ARGs). In real water environmental settings, ubiquitous complexing agents would affect the environmental behaviors of heavy metal ions due to the formation of metal-organic complexes. However, little is known whether the presence of complexing agents would change horizontal gene transfer due to heavy metal exposure. This study aimed to fill this gap by investigating the impacts of a typical complexing agent ethylenediaminetetraacetic acid (EDTA) on the conjugative transfer of plasmid-mediated ARGs induced by a range of heavy metal ions. At the environmentally relevant concentration (0.64 mg L-1) of metal ions, all the tested metal ions (Mg2+, Ca2+, Co2+, Pb2+, Ni2+, Cu2+, and Fe3+) promoted conjugative transfer of ARGs, while an inhibitory effect was observed at a relatively higher concentration (3.20 mg L-1). In contrast, EDTA (0.64 mg L-1) alleviated the effects of metal ions on ARGs conjugation transfer, evidenced by 11 %-66 % reduction in the conjugate transfer frequency. Molecular docking and dynamics simulations disclosed that this is attributed to the stronger binding of metal ions with the lipids in cell membranes. Under metal-EDTA exposure, gene expressions related to oxidative stress response, cell membrane permeability, intercellular contact, energy driving force, mobilization, and channels of plasmid transfer were suppressed compared with the metal ions exposure. This study offers insights into the alleviation mechanisms of complexing agents on ARGs transfer induced by free metal ions.

Biosafety assessment of laying hens fed different treatments of black soldier flies (Hermetia illucens) under doxycycline stress

The black soldier fly (BSF, Hermetia illucens) is a resource insect that can utilize livestock and poultry feces. However, BSFs may also increase the risk of transmission of antibiotic resistance genes (AGRs) that are widespread in livestock and poultry farm environments. Therefore, we aimed to evaluate the biosecurity risks of different BSF treatments in the laying chicken food chain using the "chicken manure-BSF-laying hens" model. Our results indicated that different BSF treatments significantly affected antibiotic residue, ARGs, MGEs, bacterial antibiotic resistance, and bacterial microbial community composition in the food chain of laying hens fed BSFs. These risks can be effectively reduced through starvation treatment and high-temperature grinding treatment. Comprehensive risk assessment analysis revealed that starvation combined with high-temperature milling (Group H) had the greatest effect.

Chlorite and bromate alter the conjugative transfer of antibiotic resistance genes: Co-regulation of oxidative stress and energy supply

The widespread use of disinfectants during the global response to the 2019 coronavirus pandemic has increased the co-occurrence of disinfection byproducts (DBPs) and antibiotic resistance genes (ARGs). Although DBPs pose major threats to public health globally, there is limited knowledge regarding their biological effects on ARGs. This study aimed to investigate the effects of two inorganic DBPs (chlorite and bromate) on the conjugative transfer of RP4 plasmid among Escherichia coli strains at environmentally relevant concentrations. Interestingly, the frequency of conjugative transfer was initially inhibited when the exposure time to chlorite or bromate was less than 24 h. However, this inhibition transformed into promotion when the exposure time was extended to 36 h. Short exposures to chlorite or bromate were shown to impede the electron transport chain, resulting in an ATP shortage and subsequently inhibiting conjugative transfer. Consequently, this stimulates the overproduction of reactive oxygen species (ROS) and activation of the SOS response. Upon prolonged exposure, the resurgent energy supply promoted conjugative transfer. These findings offer novel and valuable insights into the effects of environmentally relevant concentrations of inorganic DBPs on the conjugative transfer of ARGs, thereby providing a theoretical basis for the management of DBPs.

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.

Expanding the focus of the One Health concept: links between the Earth-system processes of the planetary boundaries framework and antibiotic resistance

The scientific community warns that our impact on planet Earth is so acute that we are crossing several of the planetary boundaries that demarcate the safe operating space for humankind. Besides, there is mounting evidence of serious effects on people's health derived from the ongoing environmental degradation. Regarding human health, the spread of antibiotic resistant bacteria is one of the most critical public health issues worldwide. Relevantly, antibiotic resistance has been claimed to be the quintessential One Health issue. The One Health concept links human, animal, and environmental health, but it is frequently only focused on the risk of zoonotic pathogens to public health or, to a lesser extent, the impact of contaminants on human health, i.e., adverse effects on human health coming from the other two One Health "compartments". It is recurrently claimed that antibiotic resistance must be approached from a One Health perspective, but such statement often only refers to the connection between the use of antibiotics in veterinary practice and the antibiotic resistance crisis, or the impact of contaminants (antibiotics, heavy metals, disinfectants, etc.) on antibiotic resistance. Nonetheless, the nine Earth-system processes considered in the planetary boundaries framework can be directly or indirectly linked to antibiotic resistance. Here, some of the main links between those processes and the dissemination of antibiotic resistance are described. The ultimate goal is to expand the focus of the One Health concept by pointing out the links between critical Earth-system processes and the One Health quintessential issue, i.e., antibiotic resistance.

Understanding Stimulation of Conjugal Gene Transfer by Nonantibiotic Compounds: How Far Are We?

A myriad of nonantibiotic compounds is released into the environment, some of which may contribute to the dissemination of antimicrobial resistance by stimulating conjugation. Here, we analyzed a collection of studies to (i) identify patterns of transfer stimulation across groups and concentrations of chemicals, (ii) evaluate the strength of evidence for the proposed mechanisms behind conjugal stimulation, and (iii) examine the plausibility of alternative mechanisms. We show that stimulatory nonantibiotic compounds act at concentrations from 1/1000 to 1/10 of the minimal inhibitory concentration for the donor strain but that stimulation is always modest (less than 8-fold). The main proposed mechanisms for stimulation via the reactive oxygen species/SOS cascade and/or an increase in cell membrane permeability are not unequivocally supported by the literature. However, we identify the reactive oxygen species/SOS cascade as the most likely mechanism. This remains to be confirmed by firm molecular evidence. Such evidence and more standardized and high-throughput conjugation assays are needed to create technologies and solutions to limit the stimulation of conjugal gene transfer and contribute to mitigating global antibiotic resistance.

Carbonaceous particulate matter promotes the horizontal transfer of antibiotic resistance genes

There is growing concern about the transfer of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) in airborne particulate matter. In this study, we investigated the effects of various types of carbonaceous particulate matter (CPM) on the transfer of ARGs in vitro. The results showed that CPM promoted the transfer of ARGs, which was related to the concentration and particle size. Compared with the control group, the transfer frequency was 95.5, 74.7, 65.4, 14.7, and 3.8 times higher in G (graphene), CB (carbon black), NGP (nanographite powder), GP1.6 (graphite powder 1.6 micron), and GP45 (graphite powder 45 micron) groups, respectively. Moreover, the transfer frequency gradually increased with the increase in CPM concentration, while there was a negative relationship between the CPM particle size and conjugative transfer frequency. In addition, the results showed that CPM could promote the transfer of ARGs by increasing ROS, as well as activating the SOS response and expression of conjugative transfer-related genes (trbBp, trfAp, korA, kroB, and trbA). These findings are indicative of the potential risk of CPM for the transfer of ARGs in the environment, enriching our understanding of environmental pollution and further raising awareness of environmental protection.

Understanding associations between antimicrobial agents usage and antimicrobial resistance genes prevalence at the community level using wastewater-based epidemiology: A Spanish pilot study

Understanding the development and spread of antimicrobial resistance (AMR) is important for combating this global threat for public health. Wastewater-based epidemiology (WBE) is a complementary approach to current surveillance programs that minimizes some of the existing limitations. The aim of the present study is to explore WBE for monitoring antibiotics and antibiotic resistance genes (ARGs) in wastewater samples collected during 2021/2022 from the city of Castellon (Spain). Eighteen commonly prescribed antibiotics have been selected and measured by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), with triple quadrupole mass analysers. Moreover, qPCR for specific ARGs has been performed to obtain information of these genes in co-presence with antibiotics. All selected ARGs, along with a total of 11 antibiotics, were identified. The highest population-normalized daily loads were observed for the macrolide azithromycin, followed by the quinolones ciprofloxacin and levofloxacin. Subsequently, daily consumption estimates based on wastewater data were compared with prescription data of antibiotics. Statistical analyses were conducted to explore if there is correlation between antibiotics and ARGs. While no correlations were found between antibiotics and their corresponding ARGs, certain correlations (p < 0.05) were identified among non-corresponding ARGs. In addition, a strong positive correlation was found between the sum of all antibiotics and the intl1 gene. Moreover, population-normalized ARG loads significantly correlate with the 16S rRNA-normalized ARG loads, serving as an indicator for population size. Results provide a baseline for future work and a proof-of-concept emphasising the need for future work and long-term surveillance, and highlight the need of similar programs at a regional and global levels worldwide.

Landscape of plasmids encoding β-lactamases in disinfection residual Enterobacteriaceae from wastewater treatment plants

Conventional disinfection processes, such as chlorination and UV radiation, are ineffective in controling antibiotic-resistant bacteria, especially disinfection residual Enterobacteriaceae (DRE) encoding β-lactamases, some of which have been classified as "critical priority pathogens" by the World Health Organization. However, few studies have focused on the transferability, phenotype, and genetic characteristics of DRE-derived plasmids encoding β-lactamases, especially extended-spectrum β-lactamases and carbapenemases. In this study, we isolated 10 typical DRE harboring plasmid-mediated blaNDM, blaCTX-M, or blaTEM in post-disinfection effluent from two wastewater treatment plants (WWTPs), with transfer frequency ranging from 1.69 × 10-6 to 3.02 × 10-5. According to genomic maps of plasmids, all blaNDM and blaTEM were cascaded with IS26, and blaCTX-M was adjacent to ISEcp1 or IS26, indicating the important role of these elements in the movement of β-lactamase-encoding genes. The presence of intact class 1 integrons on pWTPN-01 and pWTPC-03 suggested the ability of these DRE-derived plasmids to integrate other exogenous antibiotic resistance genes (ARGs). The coexistence of antibiotic, disinfectant, and heavy metal resistance genes on the same plasmid (e.g., pWTPT-03) implied the facilitating role of disinfectants and heavy metals in the transmission of DRE-derived ARGs. Notably, two plasmid transconjugants exhibited no discernible competitive fitness cost, suggesting a heightened environmental persistence. Furthermore, enhanced virulence induced by β-lactamase-encoding plasmids in their hosts was confirmed using Galleria mellonella infection models, which might be attributed to plasmid-mediated virulence genes. Overall, this study describes the landscape of β-lactamase-encoding plasmids in DRE, and highlights the urgent need for advanced control of DRE to keep environmental and ecological security.

Cylindrospermopsin enhances the conjugative transfer of plasmid-mediated multi-antibiotic resistance genes through glutathione biosynthesis inhibition

Cylindrospermopsin (CYN), a cyanobacterial toxin, has been detected in the global water environment. However, information concerning the potential environmental risk of CYN is limited, since the majority of previous studies have mainly focused on the adverse health effects of CYN through contaminated drinking water. The present study reported that CYN at environmentally relevant levels (0.1-100 μg/L) can significantly enhance the conjugative transfer of RP4 plasmid in Escherichia coli genera, wherein application of 10 μg/L of CYN led to maximum fold change of ∼6.5- fold at 16 h of exposure. Meanwhile, evaluation of underlying mechanisms revealed that environmental concentration of CYN exposure could increase oxidative stress in the bacterial cells, resulting in ROS overproduction. In turn, this led to an upregulation of antioxidant enzyme-related genes to avoid ROS attack. Further, inhibition of the synthesis of glutathione (GSH) was also detected, which led to the rapid depletion of GSH in cells and thus triggered the SOS response and promoted the conjugative transfer process. Increase in cell membrane permeability, upregulation of expression of genes related to pilus generation, ATP synthesis, and RP4 gene expression were also observed. These results highlight the potential impact on the spread of antimicrobial resistance in water environments.

Molybdenum disulfide nanosheets promote the plasmid-mediated conjugative transfer of antibiotic resistance genes

The environmental safety of nanoscale molybdenum disulfide (MoS2) has attracted considerable attention, but its influence on the horizontal migration of antibiotic resistance genes and the ecological risks entailed have not been reported. This study addressed the influence of exposure to MoS2 at different concentrations up to 100 mg/L on the conjugative transfer of antibiotic resistance genes carried by RP4 plasmids with two strains of Escherichia coli. As a result, MoS2 facilitated RP4 plasmid-mediated conjugative transfer in a dose-dependent manner. The conjugation of RP4 plasmids was enhanced as much as 7-fold. The promoting effect is mainly attributable to increased membrane permeability, oxidative stress induced by reactive oxygen species, changes in extracellular polymer secretion and differential expression of the genes involved in horizontal gene transfer. The data highlight the distinct dose dependence of the conjugative transfer of antibiotic resistance genes and the need to improve awareness of the ecological and health risks of nanoscale transition metal dichalcogenides.

Host defense peptides mitigate the spread of antibiotic resistance in physiologically relevant condition

Antibiotic resistance represents a significant challenge to public health and human safety. The primary driver behind the dissemination of antibiotic resistance is the horizontal transfer of plasmids. Current conjugative transfer assay is generally performed in a standardized manner, ignoring the effect of the host environment. Host defense peptides (HDPs) possess a wide range of biological targets and play an essential role in the innate immune system. Herein, we reveal that sub-minimum inhibitory concentrations of HDPs facilitate the conjugative transfer of RP4-7 plasmid in the Luria Broth medium, and this observation is reversed in the RPMI medium, designed to simulate the host environment. Out of these HDPs, indolicidin (Ind), a cationic tridecapeptide from bovine neutrophils, significantly inhibits the conjugation of multidrug resistance plasmids in a dose-dependent manner, including blaNDM- and tet(X4)-bearing plasmids. We demonstrate that the addition of Ind to RPMI medium as the incubation substrate downregulates the expression of conjugation-related genes. In addition, Ind weakens the tricarboxylic acid cycle, impedes the electron transport chain, and disrupts the proton motive force, consequently diminishing the synthesis of adenosine triphosphate and limiting the energy supply. Our findings highlight the importance of the host-like environments for the development of horizontal transfer inhibitors and demonstrate the potential of HDPs in preventing the spread of resistance plasmids.

Machine learning reveals the selection pressure exerted by nonantibiotic pharmaceuticals at environmentally relevant concentrations on antibiotic resistance genotypes

The emergence and increasing prevalence of antibiotic resistance pose a global public risk for human health, and nonantimicrobial pharmaceuticals play an important role in this process. Herein, five nonantimicrobial pharmaceuticals, including acetaminophen (ACT), clofibric acid (CA), carbamazepine (CBZ), caffeine (CF) and nicotine (NCT), tetracycline-resistant strains, five ARGs (sul1, sul2, tetG, tetM and tetW) and one integrase gene (intI1), were detected in 101 wastewater samples during two typical sewage treatment processes including anaerobic-oxic (A/O) and biological aerated filter (BAF) in Harbin, China. The impact of nonantibiotic pharmaceuticals at environmentally relevant concentrations on both the resistance genotypes and resistance phenotypes were explored. The results showed that a significant impact of nonantibiotic pharmaceuticals at environmentally relevant concentrations on tetracycline resistance genes encoding ribosomal protection proteins (RPPs) was found, while no changes in antibiotic phenotypes, such as minimal inhibitory concentrations (MICs), were observed. Machine learning was applied to further sort out the contribution of nonantibiotic pharmaceuticals at environmentally relevant concentrations to different ARG subtypes. The highest contribution and correlation were found at concentrations of 1400-1800 ng/L for NCT, 900-1500 ng/L for ACT and 7000-10,000 ng/L for CF for tetracycline resistance genes encoding RPPs, while no significant correlation was found between the target compounds and ARGs when their concentrations were lower than 500 ng/L for NCT, 100 ng/L for ACT and 1000 ng/L for CF, which were higher than the concentrations detected in effluent samples. Therefore, the removal of nonantibiotic pharmaceuticals in WWTPs can reduce their selection pressure for resistance genes in wastewater.

Metagenomic insights into the toxicity of carbamazepine to functional microorganisms in sludge anaerobic digestion

Contaminants of emerging concern (CECs) contained in sludge, such as carbamazepine, may be toxic to microorganisms and affect the biogenesis of methane during anaerobic digestion. In this study, different scales of anaerobic digesters were constructed to investigate the inhibitory effect of carbamazepine. Results showed that carbamazepine reduced methane production by 11.3 % and 62.1 % at concentrations of 0.4 and 2 mg/g TS, respectively. Carbamazepine hindered the dissolution of organic matter and the degradation of protein. Carbamazepine inhibited some fermentative bacteria, especially uncultured Aminicenantales, whose abundance decreased by 9.5-93.4 % under carbamazepine stress. It is worth noting that most prior studies investigated the effects of CECs only based on well-known microorganisms, ignoring the metabolisms of uncultured microorganisms. Genome-predicted metabolic potential suggested that 54 uncultured metagenome-assembled genomes (MAGs) associated with acidogenesis or acetogenesis. Therein, uncultured Aminicenantales related MAGs were proved to be acetogenic fermenters, their significant reduction may be an important reason for the decrease of methane production under carbamazepine stress. The toxicity of carbamazepine to microorganisms was mainly related to the overproduction of reactive oxygen species. This study elucidates the inhibition mechanism of carbamazepine and emphasizes the indispensable role of uncultured microorganisms in anaerobic digestion.

Regulation of quorum sensing for the manipulation of conjugative transfer of antibiotic resistance genes in wastewater treatment system

The emergence and transmission of antibiotic resistance genes (ARGs) through plasmid-mediated conjugation has become a significant worldwide public health threat. Biofilms are widely recognized as the primary reservoirs for ARGs, providing favorable conditions for horizontal gene transfer. Quorum sensing (QS) plays a critical role in bacterial biofilm formation, which further influences the spread of bacterial resistance. In this study, we examined the effects of vanillin, a QS inhibitor (QSI), at subinhibitory concentrations (sub-MICs) ranging from 0 - 0.1 g/L, on the transfer of ARGs between Escherichia coli and Pseudomonas aeruginosa. Our findings indicated that vanillin at sub-MICs inhibited the conjugative transfer frequency of the RP4 plasmid. This inhibition was supported by the downregulation of plasmid transfer genes. The suppression of conjugation can mainly be attributed to the inhibition of biofilm formation, the synthesis of extracellular polymeric substances (EPS), and the secretion of virulence factors, all of which are regulated by the bacterial QS system. On the other hand, the levels of ROS and cell membrane permeability were not primary explanations for this phenomenon. Furthermore, vanillin also reduced the conjugative transfer frequency of ARGs in wastewater effluent, providing a potential approach to alleviate bacterial resistance in water environments. These findings underscore the regulatory role of QSI in controlling ARGs transfer and have significant implications for manipulating the dissemination of bacterial resistance in the environment.

Oxygen mediated mobilization and co-occurrence of antibiotic resistance in lab-scale bioreactor using metagenomic binning

Sub-lethal levels of antibiotic stimulate bacteria to generate reactive oxygen species (ROS) that promotes emergence and spread of antibiotic resistance mediated by mobile genetic elements (MGEs). Nevertheless, the influence of dissolved oxygen (DO) levels on mobility of antibiotic resistance genes (ARGs) in response to ROS-induced stress remains elusive. Thus, the study employs metagenomic assembly and binning approaches to decipher mobility potential and co-occurrence frequency of ARGs and MGEs under hyperoxic (5.5-7 mgL- 1), normoxic (2.5-4 mgL- 1), and hypoxic (0.5-1 mgL- 1) conditions in lab-scale bioreactor for 6 months. Among 163 high-quality metagenome-assembled genomes (MAGs) recovered from 13 metagenomes, 42 MAGs harboured multiple ARGs and were assigned to priority pathogen group. Total ARG count increased by 4.3 and 2.5% in hyperoxic and normoxic, but decreased by 0.53% in hypoxic conditions after 150 days. On contrary, MGE count increased by 7.3-1.3% in all the DO levels, with only two ARGs showed positive correlation with MGEs in hypoxic compared to 20 ARGs under hyperoxic conditions. Opportunistic pathogens (Escherichia, Klebsiella, Clostridium, and Proteus) were detected as potential hosts of ARGs wherein co-localisation of critical ARG gene cassette (sul1, dfr1,adeF, and qacC) were identified in class 1 integron/Tn1 family transposons. Thus, enhanced co-occurrence frequency of ARGs with MGEs in pathogens suggested promotion of ARGs mobility under oxidative stress. The study offers valuable insights into ARG dissemination and hosts dynamics that is essential for controlling oxygen-related stress for mitigating MGEs and ARGs in the environment.

Does Environmental Exposure to Pharmaceutical and Personal Care Product Residues Result in the Selection of Antimicrobial-Resistant Microorganisms, and is this Important in Terms of Human Health Outcomes?

The environment plays a critical role in the development, dissemination, and transmission of antimicrobial resistance (AMR). Pharmaceuticals and personal care products (PPCPs) enter the environment through direct application to the environment and through anthropogenic pollution. Although there is a growing body of evidence defining minimal selective concentrations (MSCs) of antibiotics and the role antibiotics play in horizontal gene transfer (HGT), there is limited evidence on the role of non-antibiotic PPCPs. Existing data show associations with the development of resistance or effects on bacterial growth rather than calculating selective endpoints. Research has focused on laboratory-based systems rather than in situ experiments, although PPCP concentrations found throughout wastewater, natural water, and soil environments are often within the range of laboratory-derived MSCs and at concentrations shown to promote HGT. Increased selection and HGT of AMR by PPCPs will result in an increase in total AMR abundance in the environment, increasing the risk of exposure and potential transmission of environmental AMR to humans. There is some evidence to suggest that humans can acquire resistance from environmental settings, with water environments being the most frequently studied. However, because this is currently limited, we recommend that more evidence be gathered to understand the risk the environment plays in regard to human health. In addition, we recommend that future research efforts focus on MSC-based experiments for non-antibiotic PPCPS, particularly in situ, and investigate the effect of PPCP mixtures on AMR. Environ Toxicol Chem 2024;43:623-636. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The Complex Interplay Between Antibiotic Resistance and Pharmaceutical and Personal Care Products in the Environment

Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are important environmental contaminants. Nonetheless, what drives the evolution, spread, and transmission of antibiotic resistance dissemination is still poorly understood. The abundance of ARB and ARGs is often elevated in human-impacted areas, especially in environments receiving fecal wastes, or in the presence of complex mixtures of chemical contaminants, such as pharmaceuticals and personal care products. Self-replication, mutation, horizontal gene transfer, and adaptation to different environmental conditions contribute to the persistence and proliferation of ARB in habitats under strong anthropogenic influence. Our review discusses the interplay between chemical contaminants and ARB and their respective genes, specifically in reference to co-occurrence, potential biostimulation, and selective pressure effects, and gives an overview of mitigation by existing man-made and natural barriers. Evidence and strategies to improve the assessment of human health risks due to environmental antibiotic resistance are also discussed. Environ Toxicol Chem 2024;43:637-652. © 2022 SETAC.

Co-selection mechanism for bacterial resistance to major chemical pollutants in the environment

Bacterial resistance is an emerging global public health problem, posing a significant threat to animal and human health. Chemical pollutants present in the environment exert selective pressure on bacteria, which acquire resistance through co-resistance, cross-resistance, co-regulation, and biofilm resistance. Resistance genes are horizontally transmitted in the environment through four mechanisms including conjugation transfer, bacterial transformation, bacteriophage transduction, and membrane vesicle transport, and even enter human bodies through the food chain, endangering human health. Although the co-selection effects of bacterial resistance to chemical pollutants has attracted widespread attention, the co-screening mechanism and co-transmission mechanisms remain unclear. Therefore, this article summarises the current research status of the co-selection effects and mechanism of environmental pollutants resistance, emphasising the necessity of studying the co-selection mechanism of bacteria against major chemical pollutants, and lays a solid theoretical foundation for conducting risk assessment of bacterial resistance.

Confounder or Confederate? The Interactions Between Drugs and the Gut Microbiome in Psychiatric and Neurological Diseases

The gut microbiome is emerging as an important factor in signaling along the gut-brain axis. The intimate physiological connection between the gut and the brain allows perturbations in the microbiome to be directly transmitted to the central nervous system and thereby contribute to psychiatric and neurological diseases. Common microbiome perturbations result from the ingestion of xenobiotic compounds including pharmaceuticals such as psychotropic drugs. In recent years, a variety of interactions between these drug classes and the gut microbiome have been reported, ranging from direct inhibitory effects on gut bacteria to microbiome-mediated drug degradation or sequestration. Consequently, the microbiome may play a critical role in influencing the intensity, duration, and onset of therapeutic effects, as well as in influencing the side effects that patients may experience. Furthermore, because the composition of the microbiome varies from person to person, the microbiome may contribute to the frequently observed interpersonal differences in the response to these drugs. In this review, we first summarize the known interactions between xenobiotics and the gut microbiome. Then, for psychopharmaceuticals, we address the question of whether these interactions with gut bacteria are irrelevant for the host (i.e., merely confounding factors in metagenomic analyses) or whether they may even have therapeutic or adverse effects.

Mechanisms Underlying the Overlooked Chiral Fungicide-Driven Enantioselective Proliferation of Antibiotic Resistance in Earthworm Intestinal Microbiome

From a "One Health" perspective, the global threat of antibiotic resistance genes (ARGs) is associated with modern agriculture practices including agrochemicals application. Chiral fungicides account for a considerable proportion of wildly used agrochemicals; however, whether and how their enantiomers lead to differential proliferation of antibiotic resistance in agricultural environments remain overlooked. Focused on the soil-earthworm ecosystem, we for the first time deciphered the mechanisms underlying the enantioselective proliferation of antibiotic resistance driven by the enantiomers of a typical chiral fungicide mandipropamid (i.e., R-MDP and S-MDP) utilizing a multiomic approach. Time-series metagenomic analysis revealed that R-MDP led to a significant enhancement of ARGs with potential mobility (particularly the plasmid-borne ARGs) in the earthworm intestinal microbiome. We further demonstrated that R-MDP induced a concentration-dependent facilitation of plasmid-mediated ARG transfer among microbes. In addition, transcriptomic analysis with verification identified the key aspects involved, where R-MDP enhanced cell membrane permeability, transfer ability, biofilm formation and quorum sensing, rebalanced energy production, and decreased cell mobility versus S-MDP. Overall, the findings provide novel insights into the enantioselective disruption of microbiome and resistome in earthworm gut by chiral fungicides and offer significant contributions to the comprehensive risk assessment of chiral agrochemicals in agroecosystems.

Promoted micropollutant degradation and structural evolution of natural organic matter by a novel S(IV)-based water treatment strategy

The ubiquity of various organic micropollutants in global water and wastewater has raised considerable concern about their cost-efficient elimination. This study reported that the novel UV365/FeTiOX/S(IV) system could accomplish superior abatement of different micropollutants (e.g., carbamazepine, CMZ) in 30-45 min with excellent reusability and stability of FeTiOX. In addition, this system functioned effectively to remove roxarsone and As(III)/As(V) by catalytic oxidation and adsorption, respectively. Mechanistic investigations suggested the dual roles of S(IV) in enhancing pollutant oxidation, i.e., promoted Fe(II)/Fe(III) cycle and photocatalysis. These processes facilitated the continuous generation of multiple oxidizing intermediates (e.g., hydroxyl radicals, sulfate radicals, and singlet oxygen), in which the last one was first proposed as the main contributor in iron-mediated S(IV)-based oxidation processes. Based on the product identification, the transformation pathways of four different micropollutants were tentatively unraveled. The in silico prediction suggested the lower environmental risks of the final reaction products than the precursors. Particularly, the structural alteration of humic acid was analyzed, indicating an increased O/C ratio after oxidative treatment. Overall, this study has implications for developing an efficient oxidation technique for removing multiple micropollutants in water and facilitating the mechanistic reactivity modulation of the S(IV)-based oxidation strategies in water treatment.

Effects of voltage and tetracycline on horizontal transfer of ARGs in microbial electrolysis cells

The abuse of antibiotics leads to the production of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Microbial electrolysis cells (MECs) have been widely applicated in the field of degrading antibiotics. ARGs were increased via horizontal transfer in single and two-chamber MECs. As one of the critical parameters in MECs, voltage has a particular impact on the ARGs transfer via horizontal transfer. However, there have been few studies of ARGs transfer under the exposure of antibiotics and voltage in MECs. In this study, five concentrations of tetracycline (0, 1, 5, 10, 20 mg/L) were selected to explore the conjugative transfer frequency of plasmid-encoded the ARGs from the donor (E. coli RP4) to receptor (E. coli HB101) in MECs, two voltages (1.5 and 2.0 V) were used to explore the conjugative transfer frequency of ARGs in MECs, then, the transfer of ARGs in MECs under the co-effect of tetracycline and voltage was explored. The results showed that the conjugative transfer frequency of ARGs was significantly increased with the increase of tetracycline concentration and voltage, respectively (p < 0.05). Under the pressure of tetracycline and voltage, the conjugative transfer frequency of ARGs is significantly enhanced with the co-effect of tetracycline and voltage (p < 0.05). The oxidative response induced by electrical stimulation promotes the overproduction of reactive oxygen species and the enhancement of cell membrane permeability of donor and recipient bacteria in MECs. These findings provide insights for studying the spread of ARGs in MECs.

Carbamazepine facilitated horizontal transfer of antibiotic resistance genes by enhancing microbial communication and aggregation

Antimicrobial resistance is a global health security issue of widespread concern. Recent studies have unveiled the potential contribution of non-antibiotics to the emergence of antimicrobial resistance. This study investigated the effect of carbamazepine, a non-antibiotic pharmaceutical, on the fate of antibiotic resistance genes (ARGs) during anaerobic digestion. The results, as revealed by both metagenomic sequencing and absolute quantification, demonstrated that carbamazepine induced the enrichment of ARGs and increased the abundance of ARGs hosts by 1.2-2.1 times. Carbamazepine facilitated microbial aggregation and intercellular communication by upregulating functional genes associated with two-component systems, quorum sensing and type IV secretion systems, thereby increasing the frequency of ARGs conjugation. Furthermore, carbamazepine induced the acquisition of ARGs by pathogens and elevated the overall pathogenic abundance. This study revealed the mechanisms of microbial self-regulation and ARGs transmission under carbamazepine stress, highlighting the potential health risks posed by non-antibiotic pharmaceuticals during the safe disposal of sludge.

Elucidating applied voltage on the fate of antibiotic resistance genes in microbial electrolysis cell: Focusing on its transmission between anolyte and biofilm microbes

Microbial electrolysis cell (MEC) system to treat wastewater containing antibiotics has been researched actively in past years. However, the fate of antibiotic resistant genes (ARGs) in MEC is not fully revealed. The effect of applied voltage on the migration of ARGs between anolyte and biofilm microbes via examining the microbial physiology and abundances of macrolide resistance genes (MRGs) and mobile genetic elements (MGEs) was elucidated in this research. Results showed that the abundance of MRGs and MGEs was decreased in the anolyte, but their abundances were increased on the electrode biofilm, indicating their transmission from anolyte to biofilm microbes. Increased applied voltage enhanced adenosine triphosphate (ATP), reactive oxygen species (ROS), and cell membrane permeability of electrode microorganisms. The structure of the electrode microbial community was shifted through applied voltage, and the abundance of electroactive microorganisms (Geobacter, Azospirillum and Dechlorobacter) was significantly improved. Network analysis revealed that Geobacter and Geothrix were potential hosts for MRGs. Therefore, the horizontal and vertical gene transfer of ARGs could be increased by the applied voltage, leading to the enriched ARGs at the electrode biofilm. This study provides evidence and insights into the transmission of ARGs between anolyte and biofilm microbes in MEC system. SYNOPSIS: This study revealed the effect of applied voltage on ARGs in MEC and the potential migration mechanism of ARGs.

Antibiotic perturbations to the gut microbiome

Antibiotic-mediated perturbation of the gut microbiome is associated with numerous infectious and autoimmune diseases of the gastrointestinal tract. Yet, as the gut microbiome is a complex ecological network of microorganisms, the effects of antibiotics can be highly variable. With the advent of multi-omic approaches for systems-level profiling of microbial communities, we are beginning to identify microbiome-intrinsic and microbiome-extrinsic factors that affect microbiome dynamics during antibiotic exposure and subsequent recovery. In this Review, we discuss factors that influence restructuring of the gut microbiome on antibiotic exposure. We present an overview of the currently complex picture of treatment-induced changes to the microbial community and highlight essential considerations for future investigations of antibiotic-specific outcomes. Finally, we provide a synopsis of available strategies to minimize antibiotic-induced damage or to restore the pretreatment architectures of the gut microbial community.

Comprehensive insights into antibiotic resistance gene migration in microalgal-bacterial consortia: Mechanisms, factors, and perspectives

With the overuse of antibiotics, antibiotic resistance gene (ARG) prevalence is gradually increasing. ARGs are considered emerging contaminants that are broadly concentrated and dispersed in most aquatic environments. Recently, interest in microalgal-bacterial biotreatment of antibiotics has increased, as eukaryotes are not the primary target of antimicrobial drugs. Moreover, research has shown that microalgal-bacterial consortia can minimize the transmission of antibiotic resistance in the environment. Unfortunately, reviews surrounding the ARG migration mechanism in microalgal-bacterial consortia have not yet been performed. This review briefly introduces the migration of ARGs in aquatic environments. Additionally, an in-depth summary of horizontal gene transfer (HGT) between cyanobacteria and bacteria and from bacteria to eukaryotic microalgae is presented. Factors influencing gene transfer in microalgal-bacterial consortia are discussed systematically, including bacteriophage abundance, environmental conditions (temperature, pH, and nutrient availability), and other selective pressure conditions including nanomaterials, heavy metals, and pharmaceuticals and personal care products. Furthermore, considering that quorum sensing could be involved in DNA transformation by affecting secondary metabolites, current knowledge surrounding quorum sensing regulation of HGT of ARGs is summarized. In summary, this review gives valuable information to promote the development of practical and innovative techniques for ARG removal by microalgal-bacterial consortia.

Impact of sertraline on biohydrogen production from alkaline anaerobic fermentation of waste activated sludge: Focusing on microbial community and metabolism

Nowadays, antidepressants are massively consumed worldwide, inevitably bringing about the concern for their latent hazard to the natural environment. This research focused on exploring the effect of sertraline (SET, a typical antidepressant) on hydrogen yields from alkaline anaerobic fermentation of waste activated sludge (WAS). The hydrogen accumulation reached the peak of 14.73 mL/g VSS (volatile suspended solids) at a SET dosage of 50 mg/kg TSS (total suspended solids), i.e., 1.90 times of that in the control fermenter. The data of Illumina high-throughput sequencing demonstrated that SET promoted the expression of genes regulating the membrane transport. Microbial community analysis suggested that some species that could degrade refractory substances were enriched after SET exposure. Finally, metabolic pathways of hydrogen production and consumption were found to be significantly affected with SET addition. This study would deepen the concept of typical antidepressants influencing energy recovery from WAS.

The honeybee gut resistome and its role in antibiotic resistance dissemination

There is now general concern about widespread antibiotic resistance, and growing evidence indicates that gut microbiota is critical in providing antibiotic resistance. Honeybee is an important pollinator; the incidence of antibiotic resistance genes in honeybee gut causes potential risks to not only its own health but also to public and animal health, for its potential disseminator role, thus receiving more attention from the public. Recent analysis results reveal that the gut of honeybee serves as a reservoir of antibiotic resistance genes, probably due to antibiotics application history in beekeeping and horizontal gene transfer from the highly polluted environment. These antibiotic resistance genes accumulate in the honeybee gut and could be transferred to the pathogen, even having the potential to spread during pollination, tending, social interactions, etc. Newly acquired resistance traits may cause fitness reduction in bacteria whereas facilitating adaptive evolution as well. This review outlines the current knowledge about the resistome in honeybee gut and emphasizes its role in antibiotic resistance dissemination.

Differential toxicity of various mineral nanoparticles to Synechocystis sp.: With and without ciprofloxacin

Mineral nanoparticles (M-NPs) are ubiquitous in aquatic environments, but their potential harms to primary producers and impacts on the toxicity of coexisting pollutants are largely unknown. Herein, the toxicity mechanisms of various M-NPs (i.e., SiO2, Fe2O3, Al2O3, and TiO2 NPs) to Synechocystis sp. in absence and presence of ciprofloxacin (CIP) were comprehensively investigated. The heteroaggregation of cells and M-NPs can hinder substrate transfer or light acquisition. The attraction between Synechocystis sp. and M-NPs increased in the order of SiO2 < Fe2O3 < Al2O3 ≈ TiO2 NPs. Therefore, SiO2 and Fe2O3 NPs exerted slight effects on physiology and proteome of Synechocystis sp.. Al2O3 NPs with the rod-like shape caused physical damage to cells. Differently, TiO2 NPs with photocatalytic activities provided photogenerated electrons for Synechocystis sp., promoting photosynthesis and the Calvin cycle for CO2 fixation. SiO2, Fe2O3, and Al2O3 NPs alleviated the toxicity of CIP in an adsorption-depended manner. Conversely, the combination of CIP and TiO2 NPs exerted more pronounced toxic effects compared to their individuals, and CIP disturbed the extracellular electron transfer from TiO2 NPs to cells. The findings highlight the different effects of TiO2 NPs from other M-NPs on cyanobacteria, either alone or in combination with CIP, and improve the understanding of toxic mechanisms of M-NPs.

Microplastics Enhance the Prevalence of Antibiotic Resistance Genes in Anaerobic Sludge Digestion by Enriching Antibiotic-Resistant Bacteria in Surface Biofilm and Facilitating the Vertical and Horizontal Gene Transfer

Antibiotic resistance genes (ARGs) and microplastics (MPs) are recognized as emerging contaminants and threats to global human health. Despite both of them being significantly detected in their "hotspots", i.e., waste activated sludge (WAS), rare studies on how MPs affect ARGs and antibiotic-resistant bacteria (ARB) in anaerobic sludge digestion are available. Herein, the fate of ARGs and ARB after exposure to MPs of three dosages (10, 30, and 80 particles/g-TS), three polymer types (LDPE, PET, and PS), and three branching extents (LDPE, LLDPE, and HDPE) in anaerobic sludge digestion was investigated. Metagenomic results indicated that all variants of MPs resulted in an increase of the relative abundance of ARGs in the digester compared to the control. The abundance of ARGs demonstrated a dosage-dependent relationship within the range from 10 to 80 particles/g-TS, resulting in an increase from 4.5 to 27.9% compared to the control. Branching structure and polymer type influence ARG level in the sludge digester as well. Mechanism studies revealed that LDPE selectively enriched potential ARB and ARGs in the surface biofilm, possibly creating a favorable environment for ARB proliferation and ARG exchange. Furthermore, vertical transfer of ARGs was facilitated by LDPE through increasing bacterial cell proliferation accompanied by the enhancement of relevant functional genes. The elevated abundance of mobile genetic elements (MGEs) and ARGs-carrying plasmids also demonstrated that MGE-mediated horizontal transfer was promoted by LDPE at 80 particles/g-TS. This effect was compounded by increased oxidative stress, cell membrane permeability, and cell cohesion, collectively facilitating horizontal ARG transfer. Consequently, both vertical and horizontal transfer of ARGs could be concurrently promoted by LDPE an in anaerobic sludge digester.

Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands

Constructed wetlands (CWs) have been identified as significant sources of micro(nano)plastics (MPs/NPs) and antibiotic resistance genes (ARGs) in aquatic environments. However, little is known about the impact of MPs/NPs exposure on horizontal gene transfer (HGT) of ARGs and shaping the corresponding ARG hosts' community. Herein, the contribution of polystyrene (PS) particles (control, 4 mm, 100 μm, and 100 nm) to ARG transfer was investigated by adding an engineered fluorescent Escherichia coli harboring RP4 plasmid-encoded ARGs into CWs. It was found MPs/NPs significantly promoted ARG transfer in a size-dependent manner in each CW medium (p < 0.05). The 100 μm-sized PS exhibited the most significant promotion of ARG transfer (p < 0.05), whereas 100 nm-sized PS induced limited promotion due to its inhibitory activity on microbes. The altered RP4-carrying bacterial communities suggested that MPs/NPs, especially 100 µm-PS, could recruit pathogenic and nitrifying bacteria to acquire ARGs. The increased sharing of RP4-carrying core bacteria in CW medium further suggested that ARGs can spread into CW microbiome using MPs/NPs as carriers. Overall, our results highlight the high risks of ARG dissemination induced by MPs/NPs exposure and emphasize the need for better control of plastic disposal to prevent the potential health threats.

Occurrence and risk assessment of pharmaceuticals in hospital wastewater in Costa Rica

This work aims to determine the occurrence, hazard and prioritization of pharmaceuticals from hospital wastewater in Costa Rica through the monitoring of 70 compounds and assessing their environmental risk through a hazard quotient approach (HQ). Moreover, the quantification of selected antibiotic resistance genes (ARGs) was conducted for the first time in this matrix in this geographical location. Thirty-four pharmaceuticals were detected, being caffeine, 1,7-dimethylxanthine, acetaminophen, ibuprofen, naproxen, ciprofloxacin and ketoprofen the most frequent (>50% of the samples). Eighteen pharmaceuticals exhibited high hazard (HQ ≥ 1), while five more showed medium hazard (1 > HQ ≥ 0.1). Prioritization, which also included frequency parameters, revealed caffeine, lovastatin, diphenhydramine, acetaminophen, ibuprofen, ciprofloxacin, and sildenafil as the compounds of major concern. Similarly, cumulative hazard per sample (ΣHQ) estimated high hazard towards aquatic organisms in every sample. All selected ARGs, except mcr-1 (polymyxin resistance), were detected. Among genes conferring resistance to beta-lactams, blaCTX-M and blaKPC were the most abundant, related to resistance to cephalosporins and carbapenems. Ecotoxicological evaluation showed mostly low toxicity towards Daphnia magna and Vibrio fischeri, contrary to the marked effect observed towards Lactuca sativa. These findings provide relevant and novel information on the risk posed by hospital wastewater and their pharmaceutical content in the Latin American environmental context.

Phylogenomics analysis of multidrug-resistant Elizabethkingia anophelis in industrial wastewater treatment plant

AIMS

This study investigated the phylogenetic relatedness of multidrug-resistant Elizabethkingia anophelis recovered from an industrial wastewater treatment plant (WWTPi).

METHODS AND RESULTS

The wastewater samples were plated in brain heart infusion agar (4 mg/L ceftazidime, 8 mg/L meropenem, and 2 mg/L polimixin). Four isolates recovered from four stages of WWTPi (influent, aeration, decantation, and treated effluent) were identified and evaluated of susceptibility profiles in the VITEK 2 system. These strains identified as E. meningoseptica were confirmed to be E. anophelis by whole genomic sequencing (Miseq-Illumina) and showed antimicrobial resistance genes of β-lactams, aminoglycosides, and tetracycline's classes. The ribosomal multilocus sequence typing showed that they belong to the rST 65620 together with clinical strains. The phylogenomic tree revealed the similarity of our strains to those belonging to sublineage 11 and the single nucleotide polymorphism analysis confirmed that they belong to a single clade.

CONCLUSIONS

To the best of our knowledge, this is the first study reporting the persistence of multidrug-resistant E. anophelis sublineage 11 along the wastewater treatment.

Graphene Quantum Dots Nonmonotonically Influence the Horizontal Transfer of Extracellular Antibiotic Resistance Genes via Bacterial Transformation

Graphene quantum dots (GQDs) coexist with antibiotic resistance genes (ARGs) in the environment. Whether GQDs influence ARG spread needs investigation, since the resulting development of multidrug-resistant pathogens would threaten human health. This study investigates the effect of GQDs on the horizontal transfer of extracellular ARGs (i.e., transformation, a pivotal way that ARGs spread) mediated by plasmids into competent Escherichia coli cells. GQDs enhance ARG transfer at lower concentrations, which are close to their environmental residual concentrations. However, with further increases in concentration (closer to working concentrations needed for wastewater remediation), the effects of enhancement weaken or even become inhibitory. At lower concentrations, GQDs promote the gene expression related to pore-forming outer membrane proteins and the generation of intracellular reactive oxygen species, thus inducing pore formation and enhancing membrane permeability. GQDs may also act as carriers to transport ARGs into cells. These factors result in enhanced ARG transfer. At higher concentrations, GQD aggregation occurs, and aggregates attach to the cell surface, reducing the effective contact area of recipients for external plasmids. GQDs also form large agglomerates with plasmids and thus hindering ARG entrance. This study could promote the understanding of the GQD-caused ecological risks and benefit their safe application.