Antibiotic Resistance In Aquatic Environments Research Articles

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.

Unseen Weapons: Bacterial Extracellular Vesicles and the Spread of Antibiotic Resistance in Aquatic Environments.

This paper sheds light on the alarming issue of antibiotic resistance (ABR) in aquatic environments, exploring its detrimental effects on ecosystems and public health. It examines the multifaceted role of antibiotic use in aquaculture, agricultural runoff, and industrial waste in fostering the development and dissemination of resistant bacteria. The intricate interplay between various environmental factors, horizontal gene transfer, and bacterial extracellular vesicles (BEVs) in accelerating the spread of ABR is comprehensively discussed. Various BEVs carrying resistance genes like blaCTX-M, tetA, floR, and sul/I, as well as their contribution to the dominance of multidrug-resistant bacteria, are highlighted. The potential of BEVs as both a threat and a tool in combating ABR is explored, with promising strategies like targeted antimicrobial delivery systems and probiotic-derived EVs holding significant promise. This paper underscores the urgency of understanding the intricate interplay between BEVs and ABR in aquatic environments. By unraveling these unseen weapons, we pave the way for developing effective strategies to mitigate the spread of ABR, advocating for a multidisciplinary approach that includes stringent regulations, enhanced wastewater treatment, and the adoption of sustainable practices in aquaculture.

A fascinating finding: The application of traditional Chinese medicine in aquaculture prevents the spread and diffusion of antibiotic resistance genes among gut microbes

Currently, the spread and proliferation of antibiotic resistance genes (ARGs) is of great concern due to the overuse of antibiotics, especially oxytetracycline (OTC), in aquaculture. Traditional Chinese medicine (TCM) has been widely used in aquaculture because of its advantages in improving the intestinal flora. However, there is a lack of direct evidence on whether TCM impacts antibiotic resistance in aquatic environments. In this article, a short-term simulated cultivation microcosm was established to investigate the ARGs distribution and microbial community composition in the gut of fish exposed to OTC and five TCMs (Emodin, Matrine, Berberin, Andrographolide and Astragalus Polysacharin) alone or in combination using 16S rRNA gene sequencing and high-throughput quantitative PCR. The results showed that TCM alone did not significantly increase the abundance of ARGs, but ARGs abundance increased when a TCM was combined with OTC, and there was no significant interaction effect between any of the TCMs and OTC (P > 0.05). Principal component analysis indicated that OTC had a stronger effect on gut resistomes than the TCMs. TCM exposure increased the ratio of beneficial intestinal bacteria (Firmicutes to Bacteroidetes), while OTC decreased this ratio. β-diversity analysis showed that TCM had a smaller effect on the intestinal microbiome than OTC. The host network of ARGs and microorganisms showed that Enterobacter, Aeromonas, and Niveibacterium may be hosts of ARGs and mobile genetic elements (MGEs). Variation partitioning analysis suggested that the effects of MGEs accounted for 17.8% and 7.1% of the variation in the ARG spectrum in the TCM and co-exposure treatment groups, respectively. Overall, this study indicates that the risk of developing and spreading ARGs in the gut environment under exposure to TCMs is lower than that under antibiotics exposure; thus, TCM may provide a solution for antibiotic-free aquaculture in the future.

Change of antibiotic resistance in Vibrio spp. during shrimp culture in Shanghai

The judicious application of antibiotics in shrimp aquaculture is vital for addressing bacterial infections, yet monitoring bacterial resistance during distinct aquaculture phases remains deficient. This study focused on tracking antibiotic resistance dynamics in Vibrio strains sourced from both shrimp and their breeding settings. Over a standard aquaculture period (day 0, 20, 40, 60, and 80), we isolated eighty-eight Vibrio cholerae and ninety Vibrio parahaemolyticus strains from water, sediment, and shrimp samples. All isolates underwent assessment for antibiotic resistance phenotype and genotype. Both Vibrio species demonstrated resistance to nine antimicrobials. Notably, Vibrio cholerae isolates exhibited resistance rates of up to 46.6% for cephazolin, 30.7% for streptomycin, and 11.4% for ampicillin. Conversely, V. parahaemolyticus isolates displayed pronounced resistance to ampicillin (100%), cephazolin (62.2%), and cefoxitin (36.7%). Moreover, we identified 38 antibiotic resistance genes (ARGs) across all samples, with a higher prevalence observed in the water. Genetic diversity and clonal origins of the Vibrio isolates were quantified using Multilocus Sequence Typing (MLST). New Sequence Types (STs) were predominant among V. cholerae (95.4% of 43 isolates) and V. parahaemolyticus (92.9% of 28 isolates). Predominantly, V. parahaemolyticus isolates formed two extensive clonal groups: CC1420 and CC744. As the shrimp cultivation period progressed, both the resistance development rate among isolates and the average ARG count within the same STs of Vibrios steadily increased. This study underscores the potential role of ARGs transmission in the aquaculture environment as a crucial conduit for Vibrio antibiotic resistance development. Insights gained contribute to understanding the dissemination and transmission of antibiotic resistance in aquaculture, aiding in devising strategies to curb antibiotic resistance in aquatic environments.

Potential of waterbodies as a reservoir of Escherichia coli pathogens and the spread of antibiotic resistance in the Indonesian aquatic environment

Abstract River contamination remains a significant public health problem worldwide, including in Indonesia. In the community, rivers are water resources for many purposes. However, indiscriminate use of antibiotics in the veterinary and medical sectors, the community habit of throwing waste into the river, the inadequate removal of human medicine compounds in WWTP, and poor industrial waste management will induce the spread of pathogenic bacteria and antibiotic resistance between the environment and humans/animals. This review aims to analyse the various factors that influence the emergence of pathogenic Escherichia coli and antimicrobial resistance bacteria (ARB) in the aquatic environment, especially in Indonesia. In conclusion, pathogenic E. coli can adjust its physiological or metabolic conditions to survive in aquatic environments and was found resistant to antibiotics. Meanwhile, this study also describes the potency of the aquatic environment in Indonesia as a vector for the spread of pathogenic E. coli and the growth of ARBs, factors involved in the evolution and spread of antibiotic resistance in aquatic environments, and possible ways to curtail microbial risk to public health and the emergence and spread of antimicrobial resistance in the aquatic environment in Indonesia.

Tracking spatio-temporal distribution and transmission of antibiotic resistance in aquatic environments by using ESBL-producing Escherichia coli as an indicator

Wastewater treatment plants (WWTPs) play an important role in the production, and transmission of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) as a convergence for human, animal, and environmental wastewater. The aim of this study was to investigate the spatio-temporal variation and influencing factors of ARB in different functional areas of the urban WWTP and the connecting rivers for 1-year monitoring using extended-spectrum β-lactamase-producing Escherichia coli (ESBL-Ec) as an indicator bacteria, and to study the transmission patterns of ARB in the aquatic environment. The results showed that ESBL-Ec isolates were identified from the WWTP (n = 219), including influent (n = 53), anaerobiotic tank (n = 40), aerobiotic tank (n = 36), activated sludge tank (n = 31), sludge thickner tank (n = 30), effluent (n = 16), and mudcake storage area (n = 13). The dehydration process can significantly remove the ESBL-Ec isolates; however, ESBL-Ec was still detected in samples collected from the effluent of the WWTP (37.0%). The detection rate of ESBL-Ec was significantly different across seasons (P < 0.05), and ambient temperature was negatively correlated with the detection rate of ESBL-Ec (P < 0.05). Furthermore, a high prevalence of ESBL-Ec isolates (29/187, 15.5%) was detected in samples collected from the river system. These findings emphasize that the high majority of ESBL-Ec in aquatic environments is alarming because it poses a significant threat to public health. Clonal transmission of ESBL-Ec isolates between the WWTP and rivers based on the spatio-temporal scale was observed by pulsed-field gel electrophoresis analysis, ST38 and ST69 ESBL-Ec clone were selected as prioritized isolates for antibiotic resistance monitoring in the aquatic environment. Further phylogenetic analysis showed human-associated (feces, blood) E. coli was the main source contributing to the presence of antibiotic resistance in aquatic environments. Longitudinal and targeted monitoring of ESBL-Ec in WWTPs and the development of effective wastewater disinfection strategies before effluent discharge from WWTPs are urgently required, to prevent and control the spread of antibiotic resistance in the environment.

Per/polyfluoroalkyl substances modulate plasmid transfer of antibiotic resistance genes: A balance between oxidative stress and energy support

Emerging contaminants can accelerate the transmission of antibiotic resistance genes (ARGs) from environmental bacteria to human pathogens via plasmid conjugation, posing a great challenge to the public health. Although the toxic effects of per/polyfluoroalkyl substances (PFAS) as persistent organic pollutants have been understood, it is still unclear whether and how PFAS modulate the transmission of ARGs. In this study, we for the first time reported that perfluorooctanoic acid (PFOA), perfluorododecanoic acid (PFDoA) and ammonium perfluoro (2-methyl-3-oxahexanoate) (GenX) at relatively low concentrations (0.01, 0.1 mg/L) promoted the conjugative transfer of plasmid RP4 within Escherichia coli, while the plasmid conjugation was inhibited by PFOA, PFDoA and GenX at relatively high concentrations (1, 10 mg/L). The non-unidirectional conjugation result was ascribed to the co-regulation of ROS overproduction, enhanced cell membrane permeability, shortage of energy support as well as l-arginine pool depletion. Taking the well-known PFOA as an example, it significantly enhanced the conjugation frequency by 1.4 and 3.4 times at relatively low concentrations (0.01, 0.1 mg/L), respectively. Exposure to PFOA resulted in enhanced cell membrane permeability and ROS overproduction in donor cells. At high concentrations of PFOA (1, 10 mg/L), although enhanced oxidative stress and cell membrane permeability still occurred, the ATP contents in E. coli decreased, which contributed to the inhibited conjugation. Transcriptome analysis further showed that the expression levels of genes related to arginine biosynthesis (argA, argC, argF, argG, argI) and transport (artJ, artM, artQ) pathways were significantly increased. Intracellular l-arginine concentration deficiency were observed at high concentrations of PFOA. With the supplementary exogenous arginine, it was demonstrated that arginine upregulated conjugation transfer- related genes (trfAp, trbBp) and restores the cell number of transconjugants in PFOA-treated group. Therefore, the inhibited conjugation at high concentrations PFOA were attributed to the shortage of ATP and the depletion of L-arginine pool. These findings provide important insights into the effect environmental concentrations of PFAS on the conjugative transfer of ARGs, and update the regulation mechanism of plasmid conjugation, which is critical for the management of antibiotic resistance in aquatic environments.

Whole-genome sequencing of Alcaligenes sp. strain MMA: insight into the antibiotic and heavy metal resistant genes.

Introduction: A wide range of pollutants, including the likes of xenobiotics, heavy metals, and antibiotics, are characteristic of marine ecosystems. The ability of the bacteria to flourish under high metal stress favors the selection of antibiotic resistance in aquatic environments. Increased use and misuse of antibiotics in medicine, agriculture, and veterinary have posed a grave concern over antimicrobial resistance. The exposure to these heavy metals and antibiotics in the bacteria drives the evolution of antibiotic and heavy metal resistance genes. In the earlier study by the author Alcaligenes sp. MMA was involved in the removal of heavy metals and antibiotics. Alcaligenes display diverse bioremediation capabilities but remain unexplored at the level of the genome. Methods: To shed light on its genome, the Alcaligenes sp. strain MMA, was sequenced using Illumina Nova Seq sequencer, which resulted in a draft genome of 3.9Mb. The genome annotation was done using Rapid annotation using subsystem technology (RAST). Given the spread of antimicrobial resistance and the generation of multi-drug resistant pathogens (MDR), the strain MMA was checked for potential antibiotic and heavy metal resistance genes Further, we checked for the presence of biosynthetic gene clusters in the draft genome. Results: Alcaligenes sp. strain MMA, was sequenced using Illumina Nova Seq sequencer, which resulted in a draft genome of 3.9Mb. The RAST analysis revealed the presence of 3685 protein-coding genes, involved in the removal of antibiotics and heavy metals. Multiple metal-resistant genes and genes conferring resistance to tetracycline, beta-lactams, and fluoroquinolones were present in the draft genome. Many types of BGCs were predicted, such as siderophore. The secondary metabolites of fungi and bacteria are a rich source of novel bioactive compounds which have the potential to in new drug candidates. Discussion: The results of this study provide information on the strain MMA genome and are valuable for the researcher in further exploitation of the strain MMA for bioremediation. Moreover, whole-genome sequencing has become a useful tool to monitor the spread of antibiotic resistance, a global threat to healthcare.

Antibiotic concentrations and antibiotic resistance in aquatic environments of the WHO Western Pacific and South-East Asia regions: a systematic review and probabilistic environmental hazard assessment

Antibiotic resistance poses human health risks, and there are concerns about the effect of environmental antibiotic residues in the selection and spread of antibiotic resistance. The aim of this study was to identify antibiotic residue levels that are likely to select for resistance and relative contributions from different aquatic sources, of various aquatic environmental compartments of the WHO Western Pacific region (WPR) and the WHO South-East Asia region (SEAR), including in China and India. A systematic review of empirical studies that measured antibiotic concentrations in aquatic environments, published between 2006 and 2019, and a probabilistic environmental hazard assessments approach, were used to identify antibiotic concentrations that are likely to select for resistance in various aquatic environmental compartments of the WPR and SEAR, including in China and India. The assessment involved the use of measured environmental concentrations and predicted no-effect concentrations (PNECs). The systematic review found 218 relevant studies of 5230 screened from the WPR and 22 relevant studies of 2625 screened from the SEAR; some of these relevant studies were largely from China (n=168) and India (n=15). 92 antibiotics in the WPR and 45 in the SEAR were detected in various aquatic compartments. Antibiotic concentrations that most likely exceeded PNECs (0-100%) were observed in wastewater, and influents and effluents of wastewater treatment plants. Antibiotic concentrations that most likely exceeded PNECs were also observed in aquatic environmental compartments. The highest risk for the development of resistance was in tap or drinking water of the WPR and China for ciprofloxacin (62·5%). The relative contributions of potential sources of antibiotic contamination in waterways, such as hospitals, municipals, livestock, and pharmaceutical manufacturing, was determined for each antibiotic. The concentrations of antibiotic residues found in wastewater and wastewater treatment plants of the WPR and SEAR make them potential hotspots for the development of antibiotic resistance, which creates human health risks from environmental exposure via drinking water. These findings can help decision makers to target risk reduction measures against environmental residues of priority antibiotics in high-risk sites, and help to focus research efforts in these world regions. Swedish Research Council.

Water quality modelling framework for evaluating antibiotic resistance in aquatic environments

In recent decades, antibiotic resistance (AR) has become a public health concern fuelled by increasing antibiotic consumption in many societies. Aquatic environments play a crucial role in AR development and spread where they receive antibiotics, antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from a number of sources such as agriculture, aquaculture and wastewater treatment plants. Modelling is an increasingly important approach to understanding AR in aquatic environments and helps identify resistance patterns of emerging concern, evaluate fate and transport, and assess infection risks as well as look into their management in the future. However, current water quality models need to be improved to deal with the development and spread of AR. Prioritising the development of fate and transport models for AR could provide insights into bacterial evolution and help manage environmental pollution. This article provides a conceptual water quality modelling framework through a concise review of methods and approaches that can be used to model and evaluate AR in aquatic environments at the watershed scale. The key steps that need to build a framework include identifying sources and loadings, modelling the fate and transport of ARB and quantifying associated risks to humans and animals. Developing modelling scenarios and management strategies based on the framework could also contribute to achieving Sustainable Development Goals 3 (good health and well-being) and 6 (clean water and sanitation).

Microbial Community Structure and Bacterial Lineages Associated with Sulfonamides Resistance in Anthropogenic Impacted Larut River

Anthropogenic activities often contribute to antibiotic resistance in aquatic environments. Larut River Malaysia is polluted with both organic and inorganic pollutants from domestic and industrial wastewater that are probably treated inadequately. The river is characterized by high biochemical oxygen demand, chemical oxygen demand, total suspended solids, ammonia, and heavy metals. In our previous study, sulfonamides (SAs) and sulfonamide resistance genes (sul) were detected in the Larut River. Hence, in this study, we further examined the microbial community structure, diversity of sulfonamide-resistant bacteria (SARB), and their resistance genes. The study also aimed at identifying cultivable bacteria potential carriers of sul genes in the aquatic environment. Proteobacteria (22.4–66.0%), Firmicutes (0.8–41.6%), Bacteroidetes (2.0–29.4%), and Actinobacteria (5.5–27.9%) were the most dominant phyla in both the effluents and river waters. SARB isolated consisted only 4.7% of the total genera identified, with SAR Klebsiella as the most dominant (38.0–61.3%) followed by SAR Escherichia (0–22.2%) and Acinetobacter (3.2–16.0%). The majority of the SAR Klebsiella isolated from the effluents and middle downstream were positive for sul genes. Sul genes-negative SAR Escherichia and Acinetobacter were low (&lt;20%). Canonical-correlation analysis (CCA) showed that SAs residues and inorganic nutrients exerted significant impacts on microbial community and total sul genes. Network analysis identified 11 SARB as potential sul genes bacterial carriers. These findings indicated that anthropogenic activities exerted impacts on the microbial community structure and SAs resistance in the Larut River.

Antibiotic and Heavy Metal Susceptibility of Non-Cholera Vibrio Isolated from Marine Sponges and Sea Urchins: Could They Pose a Potential Risk to Public Health?

Vibrio is an important human and animal pathogen that can carry clinically relevant antibiotic resistance genes and is present in different aquatic environments. However, there is a knowledge gap between antibiotic and heavy metal resistance and virulence potential when it is part of the microbiota from marine invertebrates. Here, we aimed to evaluate these characteristics and the occurrence of mobile genetic elements. Of 25 non-cholera Vibrio spp. from marine sponges and sea urchins collected at the coastlines of Brazil and France analyzed in this study, 16 (64%) were non-susceptible to antibiotics, and two (8%) were multidrug-resistant. Beta-lactam resistance (blaSHV) and virulence (vhh) genes were detected in sponge-associated isolates. The resistance gene for copper and silver (cusB) was detected in one sea urchin isolate. Plasmids were found in 11 (44%) of the isolates. This new information allows a better comprehension of antibiotic resistance in aquatic environments, since those invertebrates host resistant Vibrio spp. Thus, Vibrio associated with marine animals may pose a potential risk to public health due to carrying these antibiotic-resistant genes.

Enhanced solar photodegradation of a plasmid-encoded extracellular antibiotic resistance gene in the presence of free chlorine

The rapid spread of antibiotic resistance in aquatic environments is closely related to the prevalence of antibiotic resistance genes (ARGs). Environmental ARGs undergo some degree of solar photolysis and chlorine oxidation. This report is the first study to comprehensively investigate the solar photodegradation mechanism of a plasmid-encoded extracellular antibiotic resistance gene (pUC19) via the solar/free chlorine process. The pUC19 degradation rate via the solar/free chlorine process was significantly enhanced (1.15 ± 0.05 min−1) compared to chlorination (0.04 min−1) and direct solar photolysis (0.05 min−1) alone. Increasing the pH values from 6 to 8 resulted in a higher yield of ozone and accelerated pUC19 photodegradation. Within 20 min of the reaction time, ozone and hydroxyl radicals (•OH) were responsible for 37.5% and 55.1% of the pUC19 degradation, respectively, and the contribution of reactive chlorine species (RCS) was negligible. Degradation rates, determined by different amplicon lengths in the same segment, showed a linear correlation with amplicon length. The attack by solar/free chlorine may be nonselective because similar amplicon lengths located in different pUC19 segments (ampR and ori) showed similar degradation rates. The pUC19 lesions caused by the solar/free chlorine process were the most effective treatment for breaking DNA double bonds. An enhanced solar/free chlorine photolysis phenomenon was also observed in real swimming pool waters, despite interference and inhibition by the water matrix components, which provides valuable insight into the control of ARGs in chlorine-receiving aquatic environments.

Simultaneous removal of micropollutants, antibiotic resistant bacteria, and antibiotic resistance genes using graphitic carbon nitride under simulated solar irradiation

The prevalence of micropollutants (MPs) and antibiotic resistance in aquatic environments has raised increasing concern for public health and ecological security. Conventional wastewater treatment processes have limited efficiency to remove these emerging contaminants. Recently, photocatalytic processes have been proposed as a promising solution to achieve enhanced performance, but there are very few studies focusing on simultaneous removal of both chemical and biological contaminants. To test the technical feasibility of a “one-stop” photocatalytic process, we evaluated the photocatalytic performance of a urea-based graphitic carbon nitride (g-C3N4) for simultaneous removal of multiple MPs, as well as antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). After a 10 min treatment under simulated solar irradiation, five MPs including sulfamethoxazole, diclofenac, mecoprop, benzotriazole, and carbamazepine (10 µg/L each) were effectively removed from spiked MilliQ water (88% of total removal efficiency) and real wastewater effluent (83% of total removal efficiency), respectively. In addition, 6.2-log reduction (complete inactivation) and 4.3-log reduction of ARB were observed after 60 min reaction in MilliQ water and real wastewater effluent, respectively. Moreover, ARB lost their self-repair function after the treatment. Lastly, atomic force microscopy images and qPCR analysis revealed that, not only the abundance of ARB but also extracellular ARGs (e-ARGs) decreased over the treatment peroid. Experiments trapping reactive species suggested that superoxide radicals (O2•-) and holes (h+) were the major active radicals contributing to contaminants degradation. The effective treatment performance for both chemical and biological contaminants, low manufacturing costs and ease of use make g-C3N4 a promising catalyst for application in the tertiary wastewater treatment processes.

Efficient removal of antibiotic-resistant bacteria and intracellular antibiotic resistance genes by heterogeneous activation of peroxymonosulfate on hierarchical macro-mesoporous Co3O4-SiO2 with enhanced photogenerated charges

Antibiotic resistance genes (ARGs) and their host antibiotic-resistant bacteria (ARB) are widely detected in the environment and pose a threat to human health. Traditional disinfection in water treatment plants cannot effectively remove ARGs and ARB. This study explored the potential of a heterogeneous photo-Fenton-like process utilizing a hierarchical macro-mesoporous Co3O4-SiO2 (MM CS) catalyst for activation of peroxymonosulfate (PMS) to inactivate ARB and degrade the intracellular ARGs. A typical gram-negative antibiotic-resistant bacteria called Pseudomonas sp. HLS-6 was used as a model ARB. A completed inactivation of ARB at ∼107 CFU/mL was achieved in 30 s, and an efficient removal rate of more than 4.0 log for specific ARGs (sul1 and intI1) was achieved within 60 min by the MM CS-based heterogeneous photo-Fenton-like process under visible light and neutral pH conditions. Mechanism investigation revealed that •O2− and 1O2 were the vital reactive species for ARB inactivation and ARG degradation. The formation and transformation of the active species were proposed. Furthermore, the hierarchical macro-mesoporous structure of MM CS provided excellent optical and photoelectrochemical properties that promoted the cycle of Co3+/Co2+ and the effective utilization of PMS. This process was validated to be effective in various water matrices, including deionized water, underground water, source water, and secondary effluent wastewater. Collectively, this work demonstrated that the MM CS-based heterogeneous photo-Fenton-like process is a promising technology for controlling the spread of antibiotic resistance in aquatic environments.

A critical review on the antimicrobial resistance, antibiotic residue and metagenomics‐assisted antimicrobial resistance gene detection in freshwater aquaculture environment

The emergence of antimicrobial resistance is one of the major challenges addressed by the aquaculture industry in recent years. Bacterial resistance to antibiotics is mainly due to the rampant prophylactic use of antibiotics in fish farms. The persistent nature of antibiotics in the system ultimately leads to the development of resistance in environmental bacteria; consequently, resistance can be transmitted to pathogenic and human commensal bacteria via horizontal gene transfer. Increased attention has been paid to antibiotic resistance in aquatic environments due to its significant threat to human health. High-throughput genomic technologies can be used for metagenomic surveillance of antibiotic resistance determinants in environmental bacteria. Continuous monitoring programmes and timely detection of resistant pathogens are unavoidable to curb antimicrobial resistance dissemination in the aquaculture system. The present review focuses on different sources of antimicrobial resistance in aquaculture systems, the current status of antimicrobial use, antimicrobial resistance in ornamental and food fish of freshwater systems, molecular mechanisms involved in resistance development, antibiotic residue in the aquaculture environment and metagenomics-based detection of antimicrobial resistance in the aquaculture environment.

Characterization of the genetic structure of mcr-1 gene among Escherichia coli isolates recovered from surface waters and sediments from Ecuador

Although anthropogenic activities contribute to the selection and spread of antibiotic resistance in aquatic environments, limited information is available from countries with absent or incomplete sewage treatment systems and the impact of their discharges onto water bodies. This study therefore aimed to characterize the genetic structure of colistin resistance (mcr) genes among Escherichia coli isolates recovered from surface waters and sediments in Ecuador. Out of 459 isolates, four Escherichia coli showed multidrug-resistant phenotypes, which harbored the mcr-1 gene and β-lactamases, such as blaTEM, blaCTX-M-15, blaCTX-M-55, or blaCTX-M-65 genes. Three E. coli isolates (U20, U30 and U144) shared a similar genetic environment surrounding the mcr-1 gene, which was located on plasmids. Only one E. coli isolate (U175) showed that the mcr-1 gene was chromosomally located. Moreover, the core genome multilocus sequence typing (cgMLST) analysis revealed that these isolates belong to different lineages. This study represents the first detection of the mcr-1 gene in multidrug-resistant E. coli isolates from environmental samples in Ecuador.

Diversity of Multidrug-Resistant Bacteria in an Urbanized River: A Case Study of the Potential Risks from Combined Sewage Overflows

Wastewater contamination and urbanization contribute to the spread of antibiotic resistance in aquatic environments. This is a particular concern in areas receiving chronic pollution of untreated waste via combined sewer overflow (CSO) events. The goal of this study was to expand knowledge of CSO impacts, with a specific focus on multidrug resistance. We sampled a CSO-impacted segment of the James River (Virginia, USA) during both clear weather and an active overflow event and compared it to an unimpacted upstream site. Bacteria resistant to ampicillin, streptomycin, and tetracycline were isolated from all samples. Ampicillin resistance was particularly abundant, especially during the CSO event, so these isolates were studied further using disk susceptibility tests to assess multidrug resistance. During a CSO overflow event, 82% of these isolates were resistant to five or more antibiotics, and 44% were resistant to seven or more. The latter statistic contrasts starkly with the upstream reference site, where only 4% of isolates displayed resistance to more than seven antibiotics. DNA sequencing (16S rRNA gene) revealed that ~35% of our isolates were opportunistic pathogens, comprised primarily of the genera Stenotrophomonas, Pseudomonas, and Chryseobacterium. Together, these results demonstrate that CSOs can be a significant source of viable clinically-relevant bacteria to the natural environment and that multidrug resistance is an important understudied component of the environmental spread of antibiotic resistance.

The Role of Gulls as Reservoirs of Antibiotic Resistance in Aquatic Environments: A Scoping Review.

The role of wildlife with long-range dispersal such as gulls in the global dissemination of antimicrobial resistance (AMR) across natural and anthropogenic aquatic environments remains poorly understood. Antibiotic-resistant bacteria have been detected in resident and migratory gulls worldwide for more than a decade, suggesting gulls as either sentinels of AMR pollution from anthropogenic sources or independent reservoirs that could maintain and disperse AMR across aquatic environments. However, confirming either of these roles remains challenging and incomplete. In this review, we present current knowledge on the geographic regions where AMR has been detected in gulls, the molecular characterization of resistance genes, and the evidence supporting the capacity of gulls to disperse AMR across regions or countries. We identify several limitations of current research to assess the role of gulls in the spread of AMR including most studies not identifying the source of AMR, few studies comparing bacteria isolated in gulls with other wild or domestic species, and almost no study performing longitudinal sampling over a large period of time to assess the maintenance and dispersion of AMR by gulls within and across regions. We suggest future research required to confirm the role of gulls in the global dispersion of AMR including the standardization of sampling protocols, longitudinal sampling using advanced satellite tracking, and whole-genome sequencing typing. Finally, we discuss the public health implications of the spread of AMR by gulls and potential solutions to limit its spread in aquatic environments.

The ecology of plasmid-coded antibiotic resistance: a basic framework for experimental research and modeling.

Many antibiotic resistance genes are associated with plasmids. The ecological success of these mobile genetic elements within microbial communities depends on varying mechanisms to secure their own propagation, not only on environmental selection. Among the most important are the cost of plasmids and their ability to be transferred to new hosts through mechanisms such as conjugation. These are regulated by dynamic control systems of the conjugation machinery and genetic adaptations that plasmid-host pairs can acquire in coevolution. However, in complex communities, these processes and mechanisms are subject to a variety of interactions with other bacterial species and other plasmid types. This article summarizes basic plasmid properties and ecological principles particularly important for understanding the persistence of plasmid-coded antibiotic resistance in aquatic environments. Through selected examples, it further introduces to the features of different types of simulation models such as systems of ordinary differential equations and individual-based models, which are considered to be important tools to understand these complex systems. This ecological perspective aims to improve the way we study and understand the dynamics, diversity and persistence of plasmids and associated antibiotic resistance genes.