Research progress on distribution, migration, transformation of antibiotics and antibiotic resistance genes (ARGs) in aquatic environment

Spatio-temporal distribution and dynamics of antibiotic resistance genes in a water-diversion lake, China

The distribution and dynamics of antibiotic resistance genes (ARGs) in water-diversion lakes are poorly understood. In this study, two comparative in situ investigations of ARG profiles targeting water diversion (DP) and non-diversion periods (NDP) were conducted in Luoma Lake, a vital transfer node for the eastern route of the South-to-North Water Diversion Project in China. The results demonstrated significant spatiotemporal variations in ARG contamination and notable differences in the co-occurrence patterns of ARGs and bacterial communities between DP and NDP. Correlations among ARGs with the 16 S rRNA, and mobile genetic elements indicate that horizontal gene transfer (HGT) and vertical gene transfer (VGT) in NDP, but only HGT in DP, were the primary mechanisms of ARG proliferation and spread, implying that water diversion could be an essential control of the transfer pattern of ARGs in a lake environment. The null model analysis indicated that stochastic processes, with predominant driver of ecological drift in the lake mainly drove the assembly of ARGs. Partial least squares structural equation modeling was developed to analyze the causal effects of the factors in shaping ARG dynamics and identify the major driving forces in the DP and NDP.

Comparative resistome analysis of Aeromonas species in aquaculture reveals antibiotic resistance patterns and phylogeographic distribution

The overuse of antibiotics in aquaculture drives the emergence of multi-drug-resistant bacteria, and antibiotic-resistant genes (ARGs) can be disseminated to other bacteria through vertical- and horizontal gene transfer (VGT and HGT) under selective pressure. Profiling the antibiotic resistome and understanding the global distribution of ARGs constitutes the first step in developing a control strategy. Hence, this study utilized extensive genomic data from hundreds of Aeromonas strains in aquaculture to profile resistome patterns and explores their association with isolation year, country, and species characteristics. Overall, ∼400 Aeromonas genomes were used to predict the ARGs from A. salmonicida, A. hydrophila, A. veronii, A. media, and A. sobria. ARGs such as sul1, tet(A), and tet(D), which display a similar proportion of positive strains among species, were subjected to phylodynamic and phylogeographic analyses. More than a hundred ARGs were identified, some of which exhibited either species-specific or non-species-specific patterns. A. salmonicida and A. media were found to have a higher proportion of species-specific ARGs than other strains, which might lead to more distinct patterns of ARG acquisition. Overall, ∼25% of strains have either sul1, tet(A), or tet(D) gene(s), but no significant difference was observed in the proportion of positive strains by species. Phylogeographic analysis revealed that the abundant numbers of sul1, tet(A), and/or tet(D) introduced in a few East Asian and North American countries could spread to both adjacent and faraway countries. In recent years, the proportions of these ARGs have dramatically increased, particularly in strains sourced from aquatic environments, suggesting control is required of the overuse of antibiotics in aquaculture. The findings of this research offer significant insights into the global dissemination of ARGs.

Unveiling the Microbiome Landscape: A Metagenomic Study of Bacterial Diversity, Antibiotic Resistance, and Virulence Factors in the Sediments of the River Ganga, India

The global rise in antibiotic resistance, fueled by indiscriminate antibiotic usage in medicine, aquaculture, agriculture, and the food industry, presents a significant public health challenge. Urban wastewater and sewage treatment plants have become key sources of antibiotic resistance proliferation. The present study focuses on the river Ganges in India, which is heavily impacted by human activities and serves as a potential hotspot for the spread of antibiotic resistance. We conducted a metagenomic analysis of sediment samples from six distinct locations along the river to assess the prevalence and diversity of antibiotic resistance genes (ARGs) within the microbial ecosystem. The metagenomic analysis revealed the predominance of Proteobacteria across regions of the river Ganges. The antimicrobial resistance (AMR) genes and virulence factors were determined by various databases. In addition to this, KEGG and COG analysis revealed important pathways related to AMR. The outcomes highlight noticeable regional differences in the prevalence of AMR genes. The findings suggest that enhancing health and sanitation infrastructure could play a crucial role in mitigating the global impact of AMR. This research contributes vital insights into the environmental aspects of antibiotic resistance, highlighting the importance of targeted public health interventions in the fight against AMR.

Deciphering the Role of WWTPs in Cold Environments as Hotspots for the Dissemination of Antibiotic Resistance Genes

Cold environments are the most widespread extreme habitats in the world. However, the role of wastewater treatment plants (WWTPs) in the cryosphere as hotspots in antibiotic resistance dissemination has not been well established. Hence, a snapshot of the resistomes of WWTPs in cold environments, below 5 °C, was provided to elucidate their role in disseminating antibiotic resistance genes (ARGs) to the receiving waterbodies. The resistomes of two natural environments from the cold biosphere were also determined. Quantitative PCR analysis of the aadA, aadB, ampC, blaSHV, blaTEM, dfrA1, ermB, fosA, mecA, qnrS, and tetA(A) genes indicated strong prevalences of these genetic determinants in the selected environments, except for the mecA gene, which was not found in any of the samples. Notably, high abundances of the aadA, ermB, and tetA(A) genes were found in the influents and activated sludge, highlighting that WWTPs of the cryosphere are critical hotspots for disseminating ARGs, potentially worsening the resistance of bacteria to some of the most commonly prescribed antibiotics. Besides, the samples from non-disturbed cold environments had large quantities of ARGs, although their ARG profiles were highly dissimilar. Hence, the high prevalences of ARGs lend support to the fact that antibiotic resistance is a common issue worldwide, including environmentally fragile cold ecosystems.

Potential Causes of Spread of Antimicrobial Resistance and Preventive Measures in One Health Perspective-A Review

Antimicrobial resistance, referring to microorganisms' capability to subsist and proliferate even when there are antimicrobials is a foremost threat to public health globally. The appearance of antimicrobial resistance can be ascribed to anthropological, animal, and environmental factors. Human-related causes include antimicrobial overuse and misuse in medicine, antibiotic-containing cosmetics and biocides utilization, and inadequate sanitation and hygiene in public settings. Prophylactic and therapeutic antimicrobial misuse and overuse, using antimicrobials as feed additives, microbes resistant to antibiotics and resistance genes in animal excreta, and antimicrobial residue found in animal-origin food and excreta are animals related contributive factors for the antibiotic resistance emergence and spread. Environmental factors including naturally existing resistance genes, improper disposal of unused antimicrobials, contamination from waste in public settings, animal farms, and pharmaceutical industries, and the use of agricultural and sanitation chemicals facilitatet its emergence and spread. Wildlife has a plausible role in the antimicrobial resistance spread. Adopting a one-health approach involving using antimicrobials properly in animals and humans, improving sanitation in public spaces and farms, and implementing coordinated governmental regulations is crucial for combating antimicrobial resistance. Collaborative and cooperative involvement of stakeholders in public, veterinary and ecological health sectors is foremost to circumvent the problem effectively.

Surface water in Lower Saxony: A reservoir for multidrug-resistant Enterobacterales

The emergence of extended-spectrum β-lactamase and carbapenemase-producing Enterobacterales (ESBL-E and CPE, respectively) is a threat to modern medicine, as infections become increasingly difficult to treat. These bacteria have been detected in aquatic environments, which raises concerns about the potential spread of antibiotic resistance through water. Therefore, we investigated the occurrence of ESBL-E and CPE in surface water in Lower Saxony, Germany, using phenotypic and genotypic methods. Water samples were collected from two rivers, five water canals near farms, and 18 swimming lakes. ESBL-E and CPE were isolated from these samples using filters and selective agars. All isolates were analyzed by whole genome sequencing. Multidrug-resistant Enterobacterales were detected in 4/25 (16%) water bodies, including 1/2 rivers, 2/5 water canals and 1/18 lakes. Among all samples, isolates belonging to five different species/species complexes were detected: Escherichia coli (n = 10), Enterobacter cloacae complex (n = 4), Citrobacter freundii (n = 3), Citrobacter braakii (n = 2), and Klebsiella pneumoniae (n = 2). Of the 21 isolates, 13 (62%) were resistant at least to 3rd generation cephalosporins and eight (38%) additionally to carbapenems. CPE isolates harbored blaKPC-2 (n = 5), blaKPC-2 and blaVIM-1 (n = 2), or blaOXA-181 (n = 1); additionally, mcr-9 was detected in one isolate. Two out of eight CPE isolates were resistant to cefiderocol and two to colistin. Resistance to 3rd generation cephalosporins was mediated by ESBL (n = 10) or AmpC (n = 3). The presence of AmpC-producing Enterobacterales, ESBL-E and CPE in northern German surface water samples is alarming and highlights the importance of aquatic environments as a potential source of MDR bacteria.

Ecotoxicological effects of antibiotic adsorption behavior of microplastics and its management measures

Microplastics adsorb heavy metals and organic pollutants to produce combined pollution. Recently, the adsorption behavior of antibiotics on microplastics has received increasing attention. Exploring the sorption behavior of pollutants on microplastics is an important reference in understanding their ecological and environmental risk studies. In this paper, by reviewing the academic literature in recent years, we clarified the current status of research on the adsorption behavior of antibiotics on microplastics, discussed its potential hazards to ecological environment and human health, and summarized the influence of factors on the adsorption mechanisms. The results show that the adsorption behavior of antibiotics on microplastics is controlled by the physical and chemical properties of antibiotics, microplastics, and water environment. Antibiotics are adsorbed on microplastics through physical and chemical interactions, which include hydrophobic interaction, partitioning, electrostatic interaction, and other non-covalent interactions. Intensity of adsorption between them is mainly determined by their physicochemical properties. The basic physicochemical properties of the aqueous environment (e.g., pH, salinity, ionic strength, soluble organic matter content, and temperature) will affect the physicochemical properties of microplastics and antibiotics (e.g., particle size, state of dispersibility, and morphology), leading to differences in the type and strength of their interactions. This paper work is expected to provide a meaningful perspective for better understanding the potential impacts of antibiotic adsorption behavior of microplastics on aquatic ecology and human health. In the meantime, some indications for future related research are provided.

Synthesis and Properties of Cefixime Core-Shell Magnetic Nano-Molecularly Imprinted Materials

Novel core-shell magnetic molecularly imprinted polymers (MMIPs) were synthesized using the sol-gel method for the adsorption of cefixime (CFX). Fe3O4@SiO2 is the core, and molecularly imprinted polymers (MIPs) are the shell, which can selectively interact with CFX. The preparation conditions, adsorption kinetics, adsorption isotherms, selective adsorption ability, and reutilization performance of the MMIPs were investigated. The adsorption capacity of MMIPs for CFX was 111.38 mg/g, which was about 3.5 times that of MNIPs. The adsorption equilibrium time was 180 min. The dynamic adsorption experiments showed that the adsorption process of MMIPs to CFX conformed to the pseudo-second-order model. Through static adsorption study, the Scatchard analysis showed that MMIPs had two types of binding sites-the high-affinity binding sites and the low-affinity binding sites-while the Langmuir model fit the adsorption isotherms well (R2 = 0.9962). Cefepime and ceftiofur were selected as the structural analogs of CFX for selective adsorption studies; the adsorption of CFX by MMIPs was higher than that of other structural analogs; and the imprinting factors of CFX, cefepime, and ceftiofur were 3.5, 1.7, and 1.4, respectively. Furthermore, the MMIPs also showed excellent reusable performance.

The Role of Stakeholders' Understandings in Emerging Antimicrobial Resistance: A One Health Approach

The increasing misuse of antibiotics in human and veterinary medicine and in agroecosystems and the consequent selective pressure of resistant strains lead to multidrug resistance (AMR), an expanding global phenomenon. Indeed, this phenomenon represents a major public health target with significant clinical implications related to increased morbidity and mortality and prolonged hospital stays. The current presence of microorganisms multi-resistant to antibiotics isolated in patients is a problem because of the additional burden of disease it places on the most fragile patients and the difficulty of finding effective therapies. In recent decades, international organizations like the World Health Organization (WHO) and the European Centre for Disease Prevention and Control (ECDC) have played significant roles in addressing the issue of AMR. The ECDC estimates that in the European Union alone, antibiotic resistance causes 33,000 deaths and approximately 880,000 cases of disability each year. The epidemiological impact of AMR inevitably also has direct economic consequences related not only to the loss of life but also to a reduction in the number of days worked, increased use of healthcare resources for diagnostic procedures and the use of second-line antibiotics when available. In 2015, the WHO, recognising AMR as a complex problem that can only be addressed by coordinated multi-sectoral interventions, promoted the One Health approach that considers human, animal, and environmental health in an integrated manner. In this review, the authors try to address why a collaboration of all stakeholders involved in AMR growth and management is necessary in order to achieve optimal health for people, animals, plants, and the environment, highlighting that AMR is a growing threat to human and animal health, food safety and security, economic prosperity, and ecosystems worldwide.

Spatial and temporal distribution of endotoxins, antibiotic resistance genes and mobile genetic elements in the air of a dairy farm in Germany

Antimicrobial resistance (AMR) is a serious issue that is continuously growing and spreading, leading to a dwindling number of effective treatments for infections that were easily treatable with antibiotics in the past. Animal farms are a major hotspot for AMR, where antimicrobials are often overused, misused, and abused, in addition to overcrowding of animals. In this study, we investigated the risk of AMR transmission from a farm to nearby residential areas by examining the overall occurrence of endotoxins, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in the air of a cattle farm. We assessed various factors, including the season and year, day and nighttime, and different locations within the farm building and its vicinity. The most abundant ARGs detected were tetW, aadA1, and sul2, genes that encode for resistances towards antibiotics commonly used in veterinary medicine. While there was a clear concentration gradient for endotoxin from the middle of the farm building to the outside areas, the abundance of ARGs and MGEs was relatively uniform among all locations within the farm and its vicinity. This suggests that endotoxins preferentially accumulated in the coarse particle fraction, which deposited quickly, as opposed to the ARGs and MGEs, which might concentrate in the fine particle fraction and remain longer in the aerosol phase. The occurrence of the same genes found in the air samples and in the manure indicated that ARGs and MGEs in the air mostly originated from the cows, continuously being released from the manure to the air. Although our atmospheric dispersion model indicated a relatively low risk for nearby residential areas, farm workers might be at greater risk of getting infected with resistant bacteria and experiencing overall respiratory tract issues due to continuous exposure to elevated concentrations of endotoxins, ARGs and MGEs in the air of the farm.

Degradation of veterinary antibiotics by Fenton process: Products identification and toxicity assessment

The aim of the work was primarily to determine the relationship between the doses of Fenton's reagents and the effectiveness of the ecotoxicity removal of aqueous solutions containing selected antibiotics. The degradation process of ampicillin, doxycycline, and tylosin in an acidic environment in the presence of H2O2 and FeSO4 was studied. The effect of reagent doses on the degree of degradation and identification of antibiotic transformation products was measured by the UPLC qTOF method. The degree of mineralisation was determined based on changes in the concentration of total organic carbon. The ecotoxicity of products was determined with commercial MARA® and MICROTOX® bioassays, as well as against unselected microorganisms from polluted rivers and wastewater treatment plant effluent. It was found that the complete degradation of antibiotics and the simultaneous elimination of the toxicity of the Fenton process products required the use of a precisely defined amount of reagents. When an insufficient dose of reactants was used, the post-reaction solutions contained antibiotic derivatives showing antimicrobial activity. On the other hand, the toxicity of the post-reaction solution against to microbiocenoses was observed when too high doses of H2O2 were used in the process. This effect resulted from the presence of unreacted reagent or other unidentified peroxides.

Prevalence of antimicrobial resistance in a full-scale drinking water treatment plant

Antibiotic resistance in drinking water has received increasing attention in recent years. In this study, the occurrence and abundance of antibiotic resistance genes (ARGs) in a drinking water treatment plant (DWTP) was comprehensively investigated using metagenomics. Bioinformatics analysis showed that 381 ARG subtypes belonging to 15 ARG types were detected, and bacitracin had the highest abundance (from 0.26 × 10-2 to 0.86 copies/cell), followed by multidrug (from 0.57 × 10-1 to 0.47 copies/cell) and sulfonamide (from 0.83 × 10-2 to 0.35 copies/cell). Additionally, 933 ARG-carrying contigs (ACCs) were obtained from the metagenomic data, among which 153 contigs were annotated as pathogens. The most abundant putative ARG host was Staphylococcus (7.9%), which most frequently carried multidrug ARGs (43.2%). Additionally, 38 high-quality metagenome-assembled genomes (MAGs) were recovered, one of which was identified as Staphylococcus aureus (Bin.624) and harboured the largest number of ARGs (n = 16). Using the cultivation technique, 60 isolates were obtained from DWTP samples, and Staphylococcus spp. (n = 11) were found to be dominant in all isolates, followed by Bacillus spp. (n = 17). Antimicrobial susceptibility testing showed that most Staphylococcus spp. were multidrug resistant (MDR). These results deepen our understanding of the distribution profiles of ARGs and antibiotic resistant bacteria (ARB) in DWTPs for potential health risk evaluation. Our study also highlights the need for new and efficient water purification technologies that can be introduced and applied in DWTPs.

Regulating mechanism of denitrifier Comamonas sp. YSF15 in response to carbon deficiency: Based on carbon/nitrogen functions and bioaggregation

There is an urgent demand to investigate mechanisms for the improvement of denitrification in carbon-deficient environment, which will effectively reduce the eutrophication in water bodies polluted by nitrate. In this study, denitrifying bacterium Comamonas sp. YSF15 was used to explore the differences in different carbon source concentrations, with the complete genome, metabolomics, and other detecting methods. Results showed that strain YSF15 was able to achieve efficient denitrification, with complete pathways for denitrification and central carbon metabolism. The carbon deficiency prompted the bacteria to use extracellular amino acid-like metabolites initially, to alleviate inhibition and maintain bioactivity, which also facilitated glycogen storage. The biogenic inhibitors (tautomycin, navitoclax, and glufosinate) at extremely low level potentially favored the competitiveness and intraspecific utilization of extracellular polysaccharides (PS). Optimal solutions for bioaggregation in carbon-deficient condition are achieved by regulating the hydrophobicity, and hydrogen bond in extracellular metabolites. The strategy contributes to the maintenance of bioactivity and adaptation to carbon deficiency. Overall, this study provides a new perspective on understanding the denitrification strategies in carbon-deficient environment, and helps to improve the nitrate removal in low-carbon wastewater treatment.

Effects of ammonia and roxithromycin exposure on skin mucus microbiota composition and immune response of juvenile yellow catfish Pelteobagrus fulvidraco

As an inevitable factor in aquaculture, ammonia plays a critical role in macrolide antibiotic resistance, leading to accumulating of antibiotic-resistant bacteria in fish skin mucus. In this study, four experimental groups were implemented to test the effects of ammonia alone or in combination with roxithromycin for 28 days on skin mucus microbial composition and the immune response of yellow catfish: CON (control), AN (50.00 mg L-1 total ammonia nitrogen, TA-N), ROX (100 μg L-1 roxithromycin), and HR (50.00 mg L-1 TA-N, 100 μg L-1 ROX). This study demonstrated that ammonia or roxithromycin exposure resulted in increased plasma ammonia content and decreased total antioxidant capacity. Compared with AN group, the combined exposure of ammonia and roxithromycin inhibited the skin mucus immune response. Microbial composition analysis showed that combined exposure of ammonia and roxithromycin had no significant effect on skin mucus α-diversity as compared with CON group. The abundance of Cetobacterium, Rhizobiales_Incertae_Sedis_uncultured and Acinetobacter was increased significantly with the combined effect of ammonia and roxithromycin, these bacteria may be potentially antibiotic-resistant. As compared with CON group, the combined exposure of ammonia and roxithromycin did not affect skin goblet cell counts. This study suggests that combined exposure to ammonia and ROX increases the risk of the emergence of antibiotic-resistant bacteria.

Photocatalytic degradation of a typical macrolide antibiotic roxithromycin using polypropylene fibre sheet supported N-TiO2/graphene oxide composite materials

The post-treatment of recycling the fine photocatalyst nanoparticles restricts their application. In this study, a new photocatalytic material was synthesized by immobilizing the N-doped TiO2 and graphene oxide (GO) composite on polypropylene (PP) (N-TiO2/GO/PP) fibre sheet, and characterized based on X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Scanning Electron Microscope (SEM). The photocatalytic activity was evaluated using roxithromycin (ROX) as a typical antibiotic pollutant. XRD, Raman spectra and SEM images proved that N-TiO2/GO/PP fibre sheet was successfully synthesized. The photocatalytic degradation of 10 mg L-1 ROX can reach up to 90% and the degradation rate constant was 0.2299 h-1 in surface water with the application amount of TiO2/GO/PP fibre sheet of 24.6 cm × 2.7 cm and reaction time of 9 h under the irradiation of simulated sunlight. The application amount of TiO2/GO/PP fibre sheet, initial concentration of ROX and water matrix significantly affect the degradation of ROX. A low concentration of natural organic matter (NOM) slightly promoted the degradation of ROX, while a high concentration of NOM significantly inhibited the degradation of ROX. Alkaline condition (pH 8-9) is favourable for the photocatalytic degradation of ROX by TiO2/GO/PP fibre sheet. The photocatalytic reactivity of the TiO2/GO/PP fibre sheet showed no significant decrease after three runs. Two primary degradation products of ROX were identified and they showed lower ecotoxicity than ROX. The results demonstrate that the new synthesized TiO2/GO/PP fibre sheet shows promising application prospects in the treatment of antibiotics in wastewater and surface waters.

Occurrence, distribution and their correlation with different parameters of antibiotics and antibiotic resistance genes in lakes of China: A review

The exposure of antibiotics and antibiotic resistance genes (ARGs) as potential threats to the environment has raised global concern. This study provides discussion on the emergence and distribution of antibiotics and ARGs in lakes. The correlation of critical water quality parameters with antibiotics and ARGs are evaluated along with their integrative potential ecological risk. Sulfonamides (∼67.18 ng/L) and quinolones (∼77.62 ng/L) were the dominant antibiotics distributed in the aqueous phase, while the quinolones and tetracyclines were the primary contamination factors in the sediment phase. The temporal and spatial distribution revealed that the antibiotic concentrations were significantly lower in summer than other seasons and the lakes in Hebei and Jiangsu provinces exhibited the highest antibiotic pollution. The detection frequency and relative abundance of sul1 gene have been the highest among all detected ARGs. Moreover, ARGs in lakes were driven by several factors, with bacterial communities and mobile genetic elements that prevailed the positive distribution of ARGs. Antibiotics have been identified as critical factors in inducing the propagation of ARGs, which could be further enhanced by chemical contaminants (e.g., heavy metals and nutrients). Involving the risk assessment strategies, research attention should be paid on three antibiotics (ofloxacin, sulfamethoxazole and erythromycin) to strengthen the policy and management of Baiyangdian Lake and East Dongting Lake. This review analysis will provide in-depth understanding to the researchers and policy-makers in formulation of strategies for remediation of antibiotic contamination in the lakes.

Effects of antibiotics on the endophyte and phyllosphere bacterial communities of lotus from above and below surface water in a typical shallow lake

Antibiotics are ubiquitous pollutants that are widely found in aquatic ecosystems, where the bacterial community of aquatic plants is influenced by antibiotics. However, differences between endophyte and phyllosphere bacteria of Lotus from above and below surface water remains unclear. Lotus samples from above and below the surface water were collected to investigate the differences in endophyte and phyllosphere bacteria and dominant environmental factors in regions with low (L-) and high (H-) total antibiotic levels. There were significant differences in Shannon diversity between endophyte and phyllosphere bacteria except between the below-surface water phyllosphere bacteria and below-surface water endophytes in both L-antibiotic and H-antibiotic regions, with higher values for phyllosphere bacteria. The dominant phylum in all phyllosphere samples was Proteobacteria (76.1%-92.5%), while Cyanobacteria (47.8%-81.1%) was dominant in all endophyte samples. The dominant source of above-surface water endophytes was below-surface water endophytes (83.68-91.25%), below-surface water phyllosphere bacteria (48.43-55.91%) for above-surface water phyllosphere bacteria, and above-surface water endophytes (53.83-61.80%) for below-surface water endophytes, while the dominant contributor to the below-surface water phyllosphere bacteria was also below-surface water endophytes (52.96-61.00%) in two regions, indicating that antibiotic stress changed the sink‒source relationship between endophytes and phyllosphere bacteria. The physical-chemical properties of surface water and sediments could be responsible for the variations in the above- and below-surface water endophytes and phyllosphere bacteria in both regions. It is suggested that antibiotics may have a substantial effect on endophyte and phyllosphere bacterial community.

Surveillance of multidrug-resistant tuberculosis in sub-Saharan Africa through wastewater-based epidemiology

The spread of multidrug-resistant tuberculosis (MDR-TB) is a serious public health issue, particularly in developing nations. The current methods of monitoring drug-resistant TB (DR-TB) using clinical diagnoses and hospital records are insufficient due to limited healthcare access and underreporting. This study proposes using Wastewater-Based Epidemiology (WBE) to monitor DR-TB in six African countries (Ghana, Nigeria, Kenya, Uganda, Cameroon, and South Africa) and examines the impact of treated wastewater on the spread of TB drug-resistant genes in the environment. Using droplet-digital polymerase chain reaction (ddPCR), the study evaluated untreated and treated wastewater samples in selected African countries for TB surveillance. There was a statistically significant difference in concentrations of genes conferring resistance to TB drugs in wastewater samples from the selected countries (p-value<0.05); South African samples exhibited the highest concentrations of 4.3(±2,77), 4.8(±2.96), 4.4(±3,10) and 4.7(±3,39) log copies/ml for genes conferring resistance to first-line TB drugs (katG, rpoB, embB and pncA respectively) in untreated wastewater. This may be attributed to the higher prevalence of TB/MDR-TB in SA compared to other African countries. Interestingly, genes conferring resistance to second-line TB drugs such as delamanid (ddn gene) and bedaquiline (atpE gene) were detected in relatively high concentrations (4.8(±3,67 and 3.2(±2,31 log copies/ml for ddn and atpE respectively) in countries, such as Cameroon, where these drugs are not part of the MDR-TB treatment regimens, perhaps due to migration or the unapproved use of these drugs in the country. The gene encoding resistance to streptomycin (rrs gene) was abundant in all countries, perhaps due to the common use of this antibiotic for infections other than TB. These results highlight the need for additional surveillance and monitoring, such as WBE, to gather data at a community level. Combining WBE with the One Health strategy and current TB surveillance systems can help prevent the spread of DR-TB in populations.

Genomic Characterization of Aeromonas veronii Provides Insights into Taxonomic Assignment and Reveals Widespread Virulence and Resistance Genes throughout the World

Aeromonas veronii is a Gram-negative bacterial species that causes disease in fish and is nowadays increasingly recurrent in enteric infections of humans. This study was performed to characterize newly sequenced isolates by comparing them with complete genomes deposited at the NCBI (National Center for Biotechnology Information). Nine isolates from fish, environments, and humans from the São Francisco Valley (Petrolina, Pernambuco, Brazil) were sequenced and compared with complete genomes available in public databases to gain insight into taxonomic assignment and to better understand virulence and resistance profiles of this species within the One Health context. One local genome and four NCBI genomes were misidentified as A. veronii. A total of 239 virulence genes were identified in the local genomes, with most encoding adhesion, motility, and secretion systems. In total, 60 genes involved with resistance to 22 classes of antibiotics were identified in the genomes, including mcr-7 and cphA. The results suggest that the use of methods such as ANI is essential to avoid misclassification of the genomes. The virulence content of A. veronii from local isolates is similar to those complete genomes deposited at the NCBI. Genes encoding colistin resistance are widespread in the species, requiring greater attention for surveillance systems.

BON domain-containing protein-mediated co-selection of antibiotic and heavy metal resistance in bacteria

The widespread antibiotic resistance of bacteria has become one of the most severe threats to public health. However, the mechanisms that allow microbial acquisition of resistance are still poorly understood. In the present study, a novel BON domain-containing protein was heterologously expressed in Escherichia coli. It functions as an efflux pump-like to confer resistance to various antibiotics, especially for ceftazidime, with a >32-fold increase in minimum inhibitory concentration (MIC). The fluorescence spectroscopy experiment indicated that BON protein could interact with several metal ions, such as copper and silver, which has been associated with the induced co-regulation of antibiotic and heavy metal resistance in bacteria. Furthermore, the BON protein was demonstrated to spontaneously self-assemble into a trimer and generate a central pore-like architecture for antibiotic transporting. A WXG motif as a molecular switch is essential for forming the transmembrane oligomeric pores and controls the interaction between BON protein and cell membrane. Based on these findings, a mechanism termed "one-in, one-out", was proposed for the first time. The present study provides new insights into the structure and function of BON protein and a previously unidentified antibiotic resistance mechanism, filling the knowledge gap in understanding BON protein-mediated intrinsic antibiotic resistance.

High prevalence and genomic characteristics of carbapenem-resistant Enterobacteriaceae and colistin-resistant Enterobacteriaceae from large-scale rivers in China

The widespread presence of carbapenem-resistant Enterobacteriaceae (CRE) and mcr-positive Escherichia coli (MCREC) poses a huge threat to both animal and human health. River water environments are vital reservoirs of antibiotic resistance genes, however, the prevalence and characteristics of CRE and MCREC from large-scale rivers in China have not been reported. In the current study, we sampled 86 rivers from four cities in Shandong Province, China in 2021 and analyzed the prevalence of CRE and MCREC. The bla_NDM/bla_KPC-2/mcr-positive isolates were characterized with methods including PCR, antimicrobial susceptibility testing, conjugation, replicon typing, whole-genome sequencing and phylogenetic analysis. We found that the prevalence of CRE and MCREC in 86 rivers was 16.3% (14/86) and 27.9% (24/86), respectively and eight rivers carried both mcr-1 and bla_NDM/bla_KPC-2. A total of 48 Enterobacteriaceae isolates (10 ST11 Klebsiella pneumoniae with bla_KPC-2, 12 bla_NDM-positive E. coli and 26 MCREC carrying only mcr-1) were obtained in this study and 47 displayed multidrug resistance (MDR). Notably, 10 of the 12 bla_NDM-positive E. coli isolates also harbored the mcr-1 gene. The bla_KPC-2 gene was located within mobile element ISKpn27-bla_KPC-2-ISKpn6 on novel F33:A-:B- non-conjugative MDR plasmids in ST11 K. pneumoniae. The dissemination of bla_NDM was mediated by transferable MDR IncB/O plasmids or IncX3 plasmids while mcr-1 was primarily disseminated by highly similar IncI2 plasmids. Notably, these waterborne IncB/O, IncX3 and IncI2 plasmids were all highly similar to previously identified plasmids from animal and human isolates. A phylogenomic analysis revealed that the CRE and MCREC isolates from water environments might be derived from animals and trigger infections in humans. The high prevalence of CRE and MCREC in large-scale environmental rivers is alarming and needs sustained surveillance due to the potential risk for transmission to humans via the food chain (irrigation) or direct contact.

The dynamics and transmission of antibiotic resistance associated with plant microbiomes

Antibiotic resistance genes (ARGs) have been widely found and studied in soil and water environments. However, the propagation of ARGs in plant microbiomes has attracted insufficient attention. Plant microbiomes, especially the rhizosphere microorganisms, are closely connected with water, soil, and air, which allows ARGs to spread widely in ecosystems and pose a threat to human health after entering the human body with bacteria. Therefore, it is necessary to deeply understand and explore the dynamics and the transmission of ARGs in rhizosphere microorganisms and endophytes of plants. In this review, the transmission and influencing factors of ARGs in the microorganisms associated with plants, especially the influence of root exudates on plant microbiomes, are analyzed. Notably, the role of intrinsic genes of plants in determining root exudates and their potential effects on ARGs are proposed and analyzed. The important role of phyllosphere microorganisms and endophytes in the transmission of ARGs and co-resistance of antibiotics and other substances are also emphasized. The proliferation and transmission of ARGs associated with plant microbiomes addressed in this review is conducive to revealing the fate of ARGs in plant microorganisms and alleviating ARG pollution.

Distribution and transmission of β-lactamase resistance genes in meal-to-milk chain on dairy farm

Antibiotics have been widely used in animal husbandry, which leads to high risk of food-borne transfer of antibiotic resistance genes (ARGs). The present study investigated the distribution of β-lactamase resistance genes (β-RGs) on dairy farm in the Songnen Plain of western Heilongjiang Province, China, to provide mechanistic insights into food-borne transmission of β-RGs through "meal-to-milk" chain under practically relevant circumstances. The results demonstrated that the abundance of β-RGs (91%) was much higher than that of other ARGs in the livestock farms. The blaTEM exhibited the content as high as 94.55% among all ARGs, and higher than 98% blaTEM was detected in meal, water and milk sample. The metagenomic taxonomy analysis indicated that the blaTEM should be carried by tnpA-04 (7.04%) and tnpA-03 (1.48%) hosted in Pseudomonas genus (15.36%) and Pantoea (29.02%) genus. Both tnpA-04 and tnpA-03 in the milk sample were identified to be the key mobile genetic elements (MGEs) responsible for transferring blaTEM along the "meal-manure-soil-surface water-milk" chain. The ARGs transfer across ecological boundaries underscored the need to evaluate potential dissemination of high-risk Proteobacteria and Bacteroidetes carried by humans and animals. They were capable of producing expanded-spectrum β-lactamases (ESBLs) and destroying commonly used antibiotics, leading to possible risk of food-borne horizontal transmission of ARGs. This study not only has important environmental implications for identifying the pathway for ARGs transfer, but also highlights the demand for appropriate policy toward safe regulation of dairy farm and husbandry products.

Influence of manure application method on veterinary medicine losses to water

Veterinary medicines are routinely used within modern animal husbandry, which results in frequent detections within animal manures and slurries. The application of manures to land as a form of organic fertiliser presents a pathway by which these bioactive chemicals can enter the environment. However, to date, there is limited understanding regarding the influence of commonly used manure application methods on veterinary medicine fate in soil systems. To bridge this knowledge gap, a semi-field study was conducted to assess the influence of commonly used application methods such as, broadcast, chisel sweep, and incorporation on veterinary medicine losses to waters. A range of veterinary medicines were selected and applied as a mixture; these were enrofloxacin, florfenicol, lincomycin, meloxicam, oxytetracycline, sulfadiazine, trimethoprim and tylosin. All the assessed veterinary medicines were detected within surface runoff and leachates, and the concentrations generally decreased throughout the irrigation period. The surface runoff concentrations ranged from 0.49 to 183.47 μg/L and 2.26-236.83 μg/L for the bare soil and grass assessments respectively. The leachate concentrations ranged from 0.04 to 309.66 μg/L and 0.33-37.79 μg/L for the bare soil and grass assessments respectively. More advanced application methods (chisel sweep) were found to significantly reduce the mass loads of veterinary medicines transported to surface runoff and leachate by 13-56% and 49-88% over that of broadcast. Incorporating pig slurries reduced the losses further with surface runoff and leachate losses being 13-56% and 49-88% lower than broadcast. Our results show that manure application techniques have a significant effect on veterinary medicine fate in the environment and as such these effects should be considered in the decision-making processes for the management of manures as well as from a risk mitigation perspective for aquatic compartments.

The role of pretreatments in handling antibiotic resistance genes in anaerobic sludge digestion - A review

Sludge is among the most important reservoirs of antibiotic resistance genes (ARGs), which would cause potential environmental risks with the sludge utilization. Currently, anaerobic digestion (AD) is effective to simultaneously realize the resource recovery and pollutants removal, including antibiotic resistance genes (ARGs), and various pretreatments are used to enhance the performance. Recently, plentiful publications have focused on the effects of pretreatment on ARGs removal, but the contradictory results are often obtained, and a comprehensive understanding of the research progress and mechanisms is essential. This study summarizes various pretreatment techniques for improving AD efficiency and ARGs reduction, investigates promising performance in ARGs removal when pretreatments combined with AD, and analyzes the potential mechanisms accounting for ARGs fates. The results showed that although thermal hydrolysis pretreatment showed the best performance in ARGs reduction during the pretreatment process, the significant rebound of ARGs would occur in the subsequent AD process. Conversely, ozone pretreatment and alkali pretreatment had no significant effect on ARGs abundance in the pretreatment stage, but could enhance ARGs removal by 15.6-24.3 % in the subsequent AD. Considering the efficiency and economic effectiveness, free nitrous acid pretreatment would be a promising and feasible option, which could enhance methane yield and ARGs removal by up to 27 % and 74.5 %, respectively. Currently, the factors determining ARGs fates during pretreatment and AD processes included the shift of microbial community, mobile genetic elements (MGEs), and environmental factors. A comprehensive understanding of the relationship between the fate of ARGs and pretreatment technologies could be helpful for systematically evaluating various pretreatments and facilitating the development of emerging and effective pretreatment techniques. Moreover, given the effectiveness, economic efficiency and environmental safety, we called for the applications of modern analysis approaches such as metagenomic and machine learning on the optimization of pretreatment conditions and revealing underlying mechanisms.

How do freshwater microalgae and cyanobacteria respond to antibiotics?

Antibiotic pollution is an emerging environmental challenge. Residual antibiotics from various sources, including municipal and industrial wastewater, sewage discharges, and agricultural runoff, are continuously released into freshwater environments, turning them into reservoirs that contribute to the development and spread of antibiotic resistance. Thus, it is essential to understand the impacts of antibiotic residues on aquatic organisms, especially microalgae and cyanobacteria, due to their crucial roles as primary producers in the ecosystem. This review summarizes the effects of antibiotics on major biological processes in freshwater microalgae and cyanobacteria, including photosynthesis, oxidative stress, and the metabolism of macromolecules. Their adaptive mechanisms to antibiotics exposure, such as biodegradation, bioadsorption, and bioaccumulation, are also discussed. Moreover, this review highlights the important factors affecting the antibiotic removal pathways by these organisms, which will promote the use of microalgae-based technology for the removal of antibiotics. Finally, we offer some perspectives on the opportunities for further studies and applications.

Dual modification based on electrostatic repulsion of bentonite and SPR effect of Bi facilitate charge transfer of Bi2WO6 for antibiotics degradation

Development of efficient photocatalysts is vital for light-driven removal of refractory antibiotics. Herein, Bi₂WO₆ microspheres were successfully anchored on the surface of bentonite, and metallic Bi was reduced in-situ by a one-step solvothermal method. Notably, the Bi/Bi₂WO₆/BT with a mass ratio of 0.15:1:0.1 exhibited the best photocatalytic activity toward degradation of tetracycline (TC) and ciprofloxacin (CIP) after 120 min of visible light irradiation, and their reaction rate constants were 8.0 and 5.5 folds higher than that of pristine Bi₂WO₆, respectively. The boosted photocatalytic activity over Bi/Bi₂WO₆/BT was ascribed to the establishment of electrostatic repulsion and SPR effect, which synergistically promoted charges transfer, thus achieving more h⁺ and ·O₂^- radical generation. Moreover, possible TC and CIP degradation pathways over Bi/Bi₂WO₆/BT were proposed based on the identified intermediates, and most of the intermediates were less toxic than TC and CIP. The study provides options to develop high-efficiency photocatalytic composites for contaminants elimination using semiconductors and readily available bentonite.

Direct Z-scheme P-TiO2/g-C3N4 heterojunction for the photocatalytic degradation of sulfa antibiotics

The construction of direct Z-scheme heterojunctions with high photocatalytic degradation ability is important for wastewater treatment, but there are still many unsolved challenges. In this article, we report the fabrication of a Z-scheme P-TiO₂/g-C₃N₄ (CNPT-X) heterostructure by the calcination method. Under simulated sunlight, CNPT-X composites are found to show excellent degradation performance against sulfonamide antibiotics sulfadiazine (SD), sulfamethazine (SM2), sulfamonomethoxine (SMM), and sulfamethoxazole (SMZ). CNPT-3 (400 mg L^-1) can be used to degrade four sulfa antibiotics within 90 min, with a degradation rate as high as 99%, which is higher than that for P-TiO₂ and g-C₃N₄ alone. The internal electron transfer paths and mechanisms for the composites are revealed by ESR radical detection experiments, XPS energy spectrum shifts, valence band positions and active material quenching experiments. Furthermore, the degradation products are analyzed by GC-MS, and four possible degradation pathways for sulfonamide pollutants are proposed. This photocatalyst provides new insights into the fundamental aspects of the photocatalytic degradation mechanism for composite pollutants, as well as new ideas for practical environmental applications.

Enrofloxacin-induced transfer of multiple-antibiotic resistance genes and emergence of novel resistant bacteria in red swamp crayfish guts and pond sediments

Antibiotic resistance genes (ARGs) can be transferred from environmental microbes to human pathogens, thus leading to bacterial infection treatment failures. The aquaculture polluted by over-used antibiotics is considered as a notorious reservoir of ARGs. However, the origin, diachronic changes, and mobility of ARGs under antibiotic exposure in aquaculture systems remain elusive. Our findings showed that enrofloxacin application also increased the relative abundance of various ARGs in addition to quinolone-resistance genes and induced ARG dissemination in crayfish gut and sediment bacteria. Further investigation indicated that the transposase-mediated recombination was the major driver of horizontal gene transfer (HGT) of ARGs under antibiotic stress. Notably, enrofloxacin application also induced the generation of some metagenome-assembled genomes (MAGs) carrying multiple ARGs, which were identified as novel species. Additionally, Enterobacteriaceae constituted a mobile ARG pool in aquaculture. Therefore, aquaculture provides potential wide environmental pathways for generation and spread of antibiotic resistance. Our findings of ARG temporal variations and dissemination pattern in aquaculture with artificial use of antibiotics are critical to the management of antibiotic resistance, which is of great ecosystem and health implications.

Occurrence, bioaccumulation and ecological risks of antibiotics in the water-plant-sediment systems in different functional areas of the largest shallow lake in North China: Impacts of river input and historical agricultural activities

Antibiotics are widely used and ubiquitous in the environment, which in turn poses potential threat to human health. However, the effects of agricultural activities and river input on the fate and ecological risks of antibiotics in shallow lake are still poorly understood. Surface water, overlying water and pore water, sediments and aquatic plant samples in the historical planting subarea (PA), historical aquaculture subarea (AU), inflow subarea (IW), discharge subarea (DC), and conservation subarea (CK) of Baiyangdian Lake were collected and analyzed. Our results revealed that the total antibiotic concentrations ranged from 85.33 ng/L to 1631.47 ng/L in waters and from 66.90 ng/g to 177.03 ng/g in sediments. Generally, the total antibiotic concentrations introduced by planting activity in surface water, overlying water and sediments were higher and the levels of total antibiotics in pore water were more affected by river input. In addition, three quinolones (QNs) and two tetracyclines (TCs) were dominant antibiotics in almost five subareas. The pseudo-partitioning coefficient k_d(pw) and bioaccumulation factor (BAF) of antibiotics varied according to the effects of river input and historical agricultural activities. The ecological risk (RQ) of antibiotics from agricultural activities was higher than that from river input. The norfloxacin (NOR) in pore water showed high RQ, which contributed to a large proportion (>50 %) of the combined ecological risks (∑RQs) except for surface water. Therefore, NOR should be used as the primary ecological risk control index for antibiotic contamination management in the BYD. ∑RQs showed high risk in water in the five subareas. This study can act as a reference for governments to formulate effective management strategies for protecting the ecological health of lakes.

Distribution and influencing factors of antibiotic resistance genes of crayfish (Procambarus clarkii) intestine in main crayfish breeding provinces in China

The propagation of antibiotic resistance genes (ARGs) has become a global public health concern. However, the distribution and influencing factors of ARGs, especially high-risk ARGs, in the gut of aquaculture animals remain unclear. Here, we employed 16S rRNA gene sequencing and high-throughput quantitative PCR techniques to determine crayfish gut microbiota and ARGs collected from 40 culture ponds in major crayfish farming provinces of China. We detected 74 ARGs in crayfish gut. Among them, the beta-lactamase and tetracycline resistance genes were dominant. The total ARG abundance was the highest in Hubei Province. High-risk ARGs were also found in crayfish gut, and ermB had the highest abundance and distributed in Anhui, Hubei, Henan and Jiangxi Province. In addition, opportunistic pathogens (Streptococcus, Aeromonas and Acinetobacter) might be potential hosts for ARGs, including high-risk ARGs. Finally, habitat, environmental factors (NO₃-N, pH and temperature), microbial alpha diversity and mobile genetic elements (MGEs) showed significant influence on ARGs profiles. Generally, our results illustrate that ARGs are prevalent in crayfish gut and may pose potential risk to human health, which will help develop targeted strategies for the risk management and assessment of ARGs in the aquaculture.

Distribution of antibiotic resistance genes in the sediments of Erhai Lake, Yunnan-Kweichow Plateau, China: Their linear relations with nonpoint source pollution discharges from 26 tributaries

Erhai Lake, a typical plateau deep water lake, experienced long-term nonpoint source (NPS) pollution discharge from 26 tributaries, which significantly affected the abundance and spread of resistance genes. In this study, 25 antibiotic resistance genes (ARGs), classified into six types, and NPS pollution discharges were investigated throughout around the Erhai basin. FCA (mexF) and sulfonamide resistance genes (sul1, sul2 and sul3) were the most common. Although the absolute overall abundance of ARGs there was low so far, the individual gene like sulfonamide resistance gene was high. Regression analysis using an ordinary least squares model (OLS) showed that the discharge of NPS pollution into Erhai Lake would have an obvious effect on the distribution of ARGs. And the relations between them were linear. Concretely speaking, the total nitrogen (TN) pollution input from tributaries could significantly correlated with the increasing of ARG abundance, while the total phosphorus (TP) pollution input showed the opposite correlation, and ultimately affect the distribution of ARGs. Moreover, the effect of TP on ARG distribution was more significant than TN. This study provides a geographical profile of ARG distribution in a subtropical deep lake on Yunnan-Kweichow Plateau. The results are beneficial for predicting the distribution characteristics of ARGs and controlling their pollution in plateau lakes.

Reliable and Representative Estimation of Extrapolation Model Application in Deriving Water Quality Criteria for Antibiotics

Deriving water quality benchmarks based on the species sensitivity distribution (SSD) is crucial for assessing the ecological risks of antibiotics. The application of extrapolation methods such as interspecies correlation estimation (ICE) and acute-to-chronic ratios (ACRs) can effectively supplement insufficient toxicity data for these emerging contaminants. Acute-to-chronic ratios can predict chronic toxicity from acute toxicity, and ICE can extrapolate an acute toxicity value from one species to another species. The present study explored the impact of two extrapolation methods on the reliability of SSDs by analyzing different scenarios. The results show that, compared with the normal and Weibull distributions, the logistic model was the best-fitting model. For most antibiotics, SSDs derived by extrapolation have high reliability, with 82.9% of R² values being higher than 0.9, and combining ICE and ACR methods can bring a maximum increase of 10% in R² . Based on the results of Monte Carlo simulation, the statistical uncertainty brought by ICE in SSD is 10-40 times larger than that brought by ACR, and combining the two methods could reduce uncertainty. In addition, the sensitivity test showed that whether the toxicity data came from extrapolation or actual measurement, the lower the value of toxicity endpoints was, the greater the bias caused by the corresponding species in every scenario. Combining the two aforementioned extrapolation methods could effectively increase the stability of SSD, with their bias nearly equal to 1. Environ Toxicol Chem 2023;42:191-204. © 2022 SETAC.

Intestinal microbiota perturbations in the gastropod Trochus niloticus concurrently exposed to ocean acidification and environmentally relevant concentrations of sulfamethoxazole

Ocean acidification (OA) and antibiotic pollution pose severe threats to the fitness of keystone species in marine ecosystems. However, the combined effects of OA and antibiotic pollution on the intestinal microbiota of marine organisms are still not well known. In this study, we exposed the herbivorous gastropod Trochus niloticus, a keystone species to maintains the stability of coral reef ecosystems, to acidic seawater (pH 7.6) and/or sulfamethoxazole (SMX, 100 ng/L, 1000 ng/L) for 28 days and determined their impacts on (1) the accumulation of SMX in the intestine of T. niloticus; (2) the characteristics of the intestinal microbiota in T. niloticus; (3) the relative abundances of sulfonamide resistance genes (i.e., sul1 and sul2) and intI1 in the intestinal microbiota of T. niloticus. Our results show that OA exposure leads to dramatic microbiota dysbiosis in the intestine of T. niloticus, including changes in bacterial community diversity and structure, decreased abundances of dominant species, existences of characteristic taxa, and altered functional predictions. In addition, SMX exposure at environmentally relevant concentrations had little effect on the intestinal microbiota of T. niloticus, whether in isolation or in combination with OA. However, after exposure to the higher SMX concentration (1000 ng/L), the accumulation of SMX in the intestine of T. niloticus could induce an increase in the copies of sul2 in the intestinal microbiota. These results suggest that the intestinal health of T. niloticus might be affected by OA and SMX, which might lead to fitness loss of the keystone species in coral reef ecosystems.

Response of microbial antibiotic resistance to pesticides: An emerging health threat

The spread of microbial antibiotic resistance has seriously threatened public health globally. Non-antibiotic stressors have significantly contributed to the evolution of bacterial antibiotic resistance. Although numerous studies have been conducted on the potential risk of pesticide pollution for bacterial antibiotic resistance, a systematic review of these concerns is still lacking. In the present study, we elaborate the mechanism underlying the effects of pesticides on bacterial antibiotic resistance acquisition as well as the propagation of antimicrobial resistance. Pesticide stress enhanced the acquisition of antibiotic resistance in bacteria via various mechanisms, including the activation of efflux pumps, inhibition of outer membrane pores for resistance to antibiotics, and gene mutation induction. Horizontal gene transfer is a major mechanism whereby pesticides influence the transmission of antibiotic resistance genes (ARGs) in bacteria. Pesticides promoted the conjugation transfer of ARGs by increasing cell membrane permeability and increased the proportion of bacterial mobile gene elements, which facilitate the spread of ARGs. This review can improve our understanding regarding the pesticide-induced generation and spread of ARGs and antibiotic resistant bacteria. Moreover, it can be applied to reduce the ecological risks of ARGs in the future.

Household Pharmaceutical Waste Disposal as a Global Problem-A Review

The negative effect of the pharmaceuticals presence (persistence?) in various components of the environment is a global problem today. These compounds are released into the environment as a result of, inter alia, their use and improper disposal. Therefore, it is important to reduce excessive drug consumption and to develop a system for the collection of unused/expired pharmaceuticals. The effectiveness of actions in this area is inextricably linked with the need to educate society on how to deal properly with unwanted medications. The aim of the study was to show that the inappropriate handling of unused/expired drugs by society is an important problem in waste management systems, and it impacts the state of the environment. Forty-eight scientific articles published between 2012 and 2021 were taken into account that discussed the systems in various countries for the collection of unused/expired pharmaceuticals. This literature review shows that the main method of disposing of unused/expired medications, according to respondents from different countries, is either by disposing of them in household waste or flushing them into the sewage system. This is also the case in countries with systems or programs for the return of redundant drugs, which indicates that these systems are not sufficiently effective. This may be influenced by many factors, including the lack or ineffective education of the society.

Efficient degradation of tylosin by Klebsiella oxytoca TYL-T1

Tylosin is widely used in livestock; however, the release of tylosin through animal manure can cause serious environmental problems. In this study, a new tylosin-degrading strain, TYL-T1, was isolated. Its phylogenetic similarity to Klebsiella oxytoca was found to be 99.17 %. TYL-T1 maintained good growth at 40 °C over a broad pH range (4.0-10). TYL-T1 degraded 99.34 % of tylosin in 36 h under optimal conditions (tylosin initial concentration: 25 mg/L, pH: 7.0, and temperature: 35 °C). After LC-MS-MS analysis, a new degradation pathway for tylosin was proposed, including ester bond breaking of the macrolide lactone ring, redox reaction, and loss of mycinose and mycarose. Based on a transcriptome analysis, 164 genes essential for degradation were upregulated through hydrolysis and redox of tylosin. Among various transferases, lipopolysaccharide methyltransferase, glycogen glucosyltransferase, and fructotransferase were responsible for tylosin degradation. The present study revealed the degradation mechanism of tylosin and highlighted the potential of Klebsiella oxytoca TYL-T1 to remove tylosin from the environment.

Presence of bromide and iodide promotes the horizontal transfer of antibiotic resistance genes during chlorination: A preliminary study

Chlorination was reported to have a great potential to increase horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs), which poses a great threat to global human health. Bromide (Br^-) and iodide (I^-) ions are widely spread ions in water and wastewater. In chlorination, Br^- and I^- can be oxidized to active bromine and iodine species. The influence of the co-existing different halogen oxidants (chlorine + bromine or iodine species) on HGT of ARGs were rarely investigated. In this study, the conjugative transfer of ARGs between a donor strain E. coli K12 and a recipient strain E. coli HB101 was investigated in chlorination without/with the presence of Br^- or I^-. Immediately after the addition of sodium hypochlorite, 53-88 % of the dosed chlorine was rapidly consumed, 10 %-42 % fast transformed into organic combined chloramines, and only low levels of free chlorine (0.02-0.8 mg/L as Cl₂) left in the diluted cultural medium. Conjugative transfer mediated by the RP4 plasmid was not significantly enhanced in chlorination without the presence of Br^- or I^-. With the presence of Br^- (0.5-5.0 mg/L) or I^- (0.05-0.5 mg/L) in chlorination, the co-existing free halogen oxidants and their organic combined ones up-regulated the mRNA expression of the oxidative stress-regulatory gene (rpoS), outer membrane protein gene (ompC), and conjugation-relevant genes (trbBp and trfAp), and caused more damage to cell entirety. As a result, the co-existing reactive halogen oxidants enhanced the HGT of ARGs probably via conjugative transfer and transformation. This study showed that the presence of Br^- and I^- of common levels in aquatic environment promoted HGT of ARGs in chlorination, thus accelerating the transmission and prevalence of ARGs.

Aquatic Environments as Hotspots of Transferable Low-Level Quinolone Resistance and Their Potential Contribution to High-Level Quinolone Resistance

The disposal of antibiotics in the aquatic environment favors the selection of bacteria exhibiting antibiotic resistance mechanisms. Quinolones are bactericidal antimicrobials extensively used in both human and animal medicine. Some of the quinolone-resistance mechanisms are encoded by different bacterial genes, whereas others are the result of mutations in the enzymes on which those antibiotics act. The worldwide occurrence of quinolone resistance genes in aquatic environments has been widely reported, particularly in areas impacted by urban discharges. The most commonly reported quinolone resistance gene, qnr, encodes for the Qnr proteins that protect DNA gyrase and topoisomerase IV from quinolone activity. It is important to note that low-level resistance usually constitutes the first step in the development of high-level resistance, because bacteria carrying these genes have an adaptive advantage compared to the highly susceptible bacterial population in environments with low concentrations of this antimicrobial group. In addition, these genes can act additively with chromosomal mutations in the sequences of the target proteins of quinolones leading to high-level quinolone resistance. The occurrence of qnr genes in aquatic environments is most probably caused by the release of bacteria carrying these genes through anthropogenic pollution and maintained by the selective activity of antimicrobial residues discharged into these environments. This increase in the levels of quinolone resistance has consequences both in clinical settings and the wider aquatic environment, where there is an increased exposure risk to the general population, representing a significant threat to the efficacy of quinolone-based human and animal therapies. In this review the potential role of aquatic environments as reservoirs of the qnr genes, their activity in reducing the susceptibility to various quinolones, and the possible ways these genes contribute to the acquisition and spread of high-level resistance to quinolones will be discussed.

Occurrence and Distribution of Antibiotics in the Water, Sediment, and Biota of Freshwater and Marine Environments: A Review

Antibiotics, as pollutants of emerging concern, can enter marine environments, rivers, and lakes and endanger ecology and human health. The purpose of this study was to review the studies conducted on the presence of antibiotics in water, sediments, and organisms in aquatic environments (i.e., seas, rivers, and lakes). Most of the reviewed studies were conducted in 2018 (15%) and 2014 (11%). Antibiotics were reported in aqueous media at a concentration of <1 ng/L−100 μg/L. The results showed that the highest number of works were conducted in the Asian continent (seas: 74%, rivers: 78%, lakes: 87%, living organisms: 100%). The highest concentration of antibiotics in water and sea sediments, with a frequency of 49%, was related to fluoroquinolones. According to the results, the highest amounts of antibiotics in water and sediment were reported as 460 ng/L and 406 ng/g, respectively. In rivers, sulfonamides had the highest abundance (30%). Fluoroquinolones (with an abundance of 34%) had the highest concentration in lakes. Moreover, the highest concentration of fluoroquinolones in living organisms was reported at 68,000 ng/g, with a frequency of 39%. According to the obtained results, it can be concluded that sulfonamides and fluoroquinolones are among the most dangerous antibiotics due to their high concentrations in the environment. This review provides timely information regarding the presence of antibiotics in different aquatic environments, which can be helpful for estimating ecological risks, contamination levels, and their management.

Quinolone distribution, trophodynamics, and human exposure risk in a transit-station lake for water diversion in east China

Quinolone antibiotics (QNs) pollution in lake environments is increasingly raising public concern due to their potential combined toxicity and associated risks. However, the spatiotemporal distribution and trophodynamics of QNs in transit-station lakes for water diversion are not well documented or understood. In this study, a comprehensive investigation of QNs in water, sediment, and aquatic fauna, including norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), and ofloxacin (OFL), was conducted in Luoma Lake, a major transit station for the eastern route of the South-to-North Water Diversion Project in China. The target QNs were widely distributed in the water (∑QNs: 70.12 ± 62.79 ng/L) and sediment samples (∑QNs: 13.35 ± 10.78 ng/g dw) in both the non-diversion period (NDP) and the diversion period (DP), where NOR and ENR were predominant. All the QNs were detected in all biotic samples in DP (∑QNs: 80.04 ± 20.59 ng/g dw). The concentration of ∑QNs in the water in NDP was significantly higher than those in DP, whereas the concentration in the sediments in NDP was comparable to those in DP. ∑QNs in the water-sediment system exhibited decreasing trends from northwest (NW) to southeast (SE) in both periods; however, the K_oc (organic carbon normalized partition coefficients) of individual QNs in DP sharply rose compared with those in NDP, which indicated that water diversion would alter the environmental fate of QNs in Luoma Lake. In DP, all QNs, excluding NOR, were all biodiluted across the food web; whereas their bioaccumulation potentials in the SE subregion were higher than those in the NW subregion, which was in contrast to the spatial distribution of their exposure concentrations. The estimated daily QN intakes via drinking water and aquatic products suggested that residents in the SE side were exposed to greater health risks, despite less aquatic pollution in the region.

Distribution and characteristics of carbapenem-resistant and extended-spectrum β-lactamase (ESBL) producing Escherichia coli in hospital effluents, sewage treatment plants, and river water in an urban area of Japan

Occurrence of profiles of the carbapenem-resistant Escherichia coli (CRE-E) and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-E) in an urban river in a sub-catchment of the Yodo River Basin, one of the representative water systems of Japan was investigated. We conducted seasonal and year-round surveys for the antimicrobial-resistant bacteria (AMRB) and antimicrobial-resistance genes (AMRGs) in hospital effluents, sewage treatment plant (STP) wastewater, and river water; subsequently, contributions to wastewater discharge into the rivers were estimated by analyses based on the mass flux. Furthermore, the characteristics of AMRB in the water samples were evaluated on the basis of antimicrobial susceptibility tests. CRE-E and ESBL-E were detected in all water samples with mean values 11 and 1900 CFU/mL in the hospital effluent, 58 and 4550 CFU/mL in the STP influent, not detected to 1 CFU/mL in the STP effluent, and 1 and 1 CFU/mL in the STP discharge into the river, respectively. Contributions of the pollution load derived from the STP effluent discharged into the river water were 1 to 21%. The resistome profiles for bla_IMP, bla_TEM, and bla_CTX-M genes in each water sample showed that AMRGs were not completely removed in the wastewater treatment process in the STP, and the relative abundances of bla_IMP, bla_TEM, and bla_CTX-M genes were almost similar (P<0.05). Susceptibility testing of antimicrobial-resistant E. coli isolates showed that CRE-E and ESBL-E detected in wastewaters and river water were linked to the prevalence of AMRB in clinical settings. These results suggest the importance of conducting environmental risk management of AMRB and AMRGs in the river environment. To our knowledge, this is the first detailed study that links the medical environment to CRE-E and ESBL-E for evaluating the AMRB and AMRGs in hospital effluents, STP wastewater, and river water at the basin scale on the basis of mass flux as well as the contributions of CRE-E and ESBL-E to wastewater discharge into the river.

Antibiotic resistant bacteria and genes in wastewater treatment plants: From occurrence to treatment strategies

This study aims to discuss the following: (1) occurrence and proliferation of antibiotic resistance in wastewater treatment plants (WWTPs); (2) factors influencing antibiotic resistance bacteria and genes in WWTPs; (3) tools to assess antibiotic resistance in WWTPs; (4) environmental contamination of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from WWTPs; (5) effects of ARB and ARGs from WWTPs on human health; and (6) treatment strategies. In general, resistant and multi-resistant bacteria, including Enterobacteriaceae, Pseudomonas aeruginosa, and Escherichia coli, exist in various processes of WWTPs. The existence of ARB and ARGs results from the high concentration of antibiotics in wastewater, which promote selective pressures on the local bacteria present in WWTPs. Thus, improving wastewater treatment technology and avoiding the misuse of antibiotics is critical to overcoming the threat of proliferation of ARBs and ARGs. Numerous factors can affect the development of ARB and ARGs in WWTPs. Abiotic factors can affect the bacterial community dynamics, thereby, affecting the applicability of ARB during the wastewater treatment process. Furthermore, the organic loads and other nutrients influence bacterial survival and growth. Specifically, molecular methods for the rapid characterization and detection of ARBs or their genes comprise DNA sequencing, real-time PCR, simple and multiplex PCR, and hybridization-based technologies, including micro- and macro-arrays. The reuse of effluent from WWTPs for irrigation is an efficient method to overcome water scarcity. However, there are also some potential environmental risks associated with this practice, such as increase in the levels of antibiotic resistance in the soil microbiome. Human mortality rates may significantly increase, as ARB can lead to resistance among several types of antibiotics or longer treatment times. Some treatment technologies, such as anaerobic and aerobic treatment, coagulation, membrane bioreactors, and disinfection processes, are considered potential techniques to restrict antibiotic resistance in the environment.

Sulfadiazine inhibits hydrogen production during sludge anaerobic fermentation by affecting pyruvate decarboxylation

The overuse and random discharge of antibiotics can cause serious environmental pollution. Sludge acts as a repository for antibiotics, its anaerobic fermentation process will inevitably be affected. This study investigated the effects of a typical antibiotic contaminant, sulfadiazine (SDZ), on the anaerobic fermentation of sludge for hydrogen production. Results demonstrated that the production of hydrogen was significantly inhibited by SDZ, and the inhibition was enhanced with increasing SDZ content. Within 5 days, the cumulative amount of hydrogen with 500 mg SDZ/kg dry sludge was 8.5 mL, which was only 32.2% of that in the control (26.4 mL). Mechanistic investigation showed that the reduced hydrogen production when SDZ existed was mainly attributed to the suppression of pyruvate decarboxylation during the hydrogen production stage, and the diversity of microorganisms, especially the abundance of microorganisms and the activities of key enzymes closely related to hydrogen production were inhibited with SDZ, resulting in less hydrogen accumulation.

Solar-light-driven LaFe x Ni1- x O3 perovskite oxides for photocatalytic Fenton-like reaction to degrade organic pollutants

LaFe _x Ni_{1- x} O₃ perovskite oxides were prepared by the sol-gel method under various conditions, including different pH values (pH 0 and pH 7) and different calcination temperatures (500-800 °C) as well as different Fe/Ni ratios (1/9, 3/7, 5/5, 7/3, 9/1). The samples were examined by XRD, DRS, BET, and SEM to reveal their crystallinity, light-absorption ability, specific surface area, and surface features, respectively. The photocatalytic Fenton reaction was conducted using various LaFe _x Ni_{1- x} O₃ perovskite oxides to decompose the methylene blue molecules. Accordingly, the synthesis condition of pH 0, calcination temperature at 700 °C, and Fe/Ni ratio = 7/3 could form LaFe_0.7Ni_0.3O₃ perovskite oxides as highly efficient photocatalysts. Moreover, various conditions during the photocatalytic degradation were verified, such as pH value, catalyst dosage, and the additional amount of H₂O₂. LaFe_0.7Ni_0.3O₃ perovskite oxides could operate efficiently under pH 3.5, catalyst dosage of 50 mg/150 mL, and H₂O₂ concentration of 133 ppm to decompose the MB dye in the 1st order kinetic rate constant of 0.0506 s^-1.

Current Progress in Natural Degradation and Enhanced Removal Techniques of Antibiotics in the Environment: A Review

Antibiotics are used extensively throughout the world and their presence in the environment has caused serious pollution. This review summarizes natural methods and enhanced technologies that have been developed for antibiotic degradation. In the natural environment, antibiotics can be degraded by photolysis, hydrolysis, and biodegradation, but the rate and extent of degradation are limited. Recently, developed enhanced techniques utilize biological, chemical, or physicochemical principles for antibiotic removal. These techniques include traditional biological methods, adsorption methods, membrane treatment, advanced oxidation processes (AOPs), constructed wetlands (CWs), microalgae treatment, and microbial electrochemical systems (such as microbial fuel cells, MFCs). These techniques have both advantages and disadvantages and, to overcome disadvantages associated with individual techniques, hybrid techniques have been developed and have shown significant potential for antibiotic removal. Hybrids include combinations of the electrochemical method with AOPs, CWs with MFCs, microalgal treatment with activated sludge, and AOPs with MFCs. Considering the complexity of antibiotic pollution and the characteristics of currently used removal technologies, it is apparent that hybrid methods are better choices for dealing with antibiotic contaminants.

Antimicrobial antibodies by phage display: Identification of antibody-based inhibitor against mycobacterium tuberculosis isocitrate lyase

The increasing incidence reports of antibiotic resistance highlights the need for alternative approaches to deal with bacterial infections. This brought about the idea of utilizing monoclonal antibodies as an alternative antibacterial treatment. Majority of the studies are focused on developing antibodies to bacterial surface antigens, with little emphasis on antibodies that inhibit the growth mechanisms of a bacteria host. Isocitrate lyase (ICL) is an important enzyme for the growth and survival of Mycobacterium tuberculosis (MTB) during latent infection as a result of its involvement in the mycobacterial glyoxylate and methylisocitrate cycles. It is postulated that the inhibition of ICL can disrupt the life cycle of MTB. To this extent, we utilized antibody phage display to identify a single chain fragment variable (scFv) antibody against the recombinant ICL protein from MTB. The soluble a-ICL-C6 scFv clone exhibited good binding characteristics with high specificity against ICL. More importantly, the clone exhibited in vitro inhibitory effect with an enzymatic assay resulting in a decrease of ICL enzymatic activity. In silico analysis showed that the scFv-ICL interactions are driven by 23 hydrogen bonds and 13 salt bridges that might disrupt the formation of ICL subunits for the tertiary structure or the formation of active site β domain. However, further validation is necessary to confirm if the isolated clone is indeed a good inhibitor against ICL for application against MTB.