Search Results (24)

Wastewater treatment plants (WWTPs) are important interfaces for the persistence and dissemination of antimicrobial resistance genes (ARGs) in the environment. This study investigated colistin resistance and the presence of mobile colistin resistance (mcr) genes in Enterobacterales isolated from a poultry slaughterhouse WWTP in Brazil. Samples were collected from raw sewage, an equalization tank, and treated effluent. A total of 27 Enterobacter spp. isolates were identified, of which 70.4% showed resistance to colistin (MIC range: 2 to ≥512 mg/L). PCR screening detected mcr-1 in two isolates and mcr-10 in three isolates distributed across all treatment stages, including the final effluent. Whole-genome sequencing of a representative isolate from treated effluent identified Enterobacter vonholyi ST3343, carrying a plasmid-borne mcr-10 gene on an ~107 kb IncFII(Yp) plasmid, along with additional resistance determinants. Phylogenetic analysis supported the classification of this gene as a novel allele, mcr-10.6. The persistence of a clonal lineage harboring mcr-10.6 throughout the treatment system indicates that conventional wastewater treatment may not effectively eliminate clinically relevant ARGs. These findings highlight treated effluent as a potential route for environmental dissemination of colistin resistance and reinforce the need for improved monitoring and mitigation strategies within a One Health framework. Full article

Background: High infectious disease burden and uncontrolled antibiotic usage across human, animal, and environmental contaminants make antimicrobial resistance (AMR) a growing public health problem in Africa. Mobile genetic elements (MGEs) such plasmids, transposons, integrons, conjugative elements, and phages help spread AMR via horizontal gene transfer (HGT) across human, animal, food, and environmental sources. Despite growing evidence for antibiotic resistance genes (ARGs), Africa lacks a one-health-focused synthesis of mobile genetic element-mediated AMR. Objective: This systematic review and meta-analysis aimed to consolidate information on MGEs and ARGs in AMR dissemination throughout Africa’s one health interface. Methods: The literature was searched using PubMed, Scopus, and ScienceDirect. Observational. molecular epidemiology, whole genome sequencing (WGS), and metagenomic investigations of MGE-associated AMR in Africa were eligible. The study selection, data extraction, and quality assessment were performed by two independent reviewer and quality was graded using ROBVIS 2 utilizing Rayyan software. Narrative synthesis, random-effect meta-analysis, subgroup analysis, and meta-regression were utilized. Results: A total of 109 studies were included, with 91 studies contributing to the meta-analysis. MGEs reported were plasmids (71.7%) and integrons (54.8%). ARGs carried by MGEs were blaCTMX-M-15 (78.6%), Sul2 (69.6%), blaTEM (59.1%), and tetA (49.9%). Horizontal gene transfer was seen in 259 instances; however, transmission was unclear. In 442 observations, transmission pathways across human, animal, and environmental interfaces showed AMR prevalence of 75.1% in human, 98.0% in human–animal, and 61.3% in one health interface. Whole-genome sequencing was the most frequently used method for detecting MGEsThe pooled pathogen and AMR prevalence rates were 73.3% (95% CI: 60.5–83.7%) and 94% (95% CI: 85–98%), with significant heterogeneity (I² = 97.8% and 97.4%, respectively). The prevalence of Escherichia coli was 93% and Salmonella enterica 85% in subgroup analysis. Fluoroquinolones, aminoglycosides, and beta-lactams were prevalent in humans (89.7%) and human–animal interactions (98.0%) according to AMR Class. Conclusions: Horizontal gene transfer has propagated MGE-mediated antimicrobial resistance across human, animal, and environmental interfaces in Africa. To combat AMR in Africa, coordinated, genomics-informed One Health surveillance and antibiotic stewardship are needed. Due to variability and publication bias, these data should be considered cautiously. Pooled data may only show descriptive patterns, and not necessarily precise continent-wide prevalence estimates. Full article

Background/Objectives: Freshwater microalgae–bacteria consortia are increasingly utilized in wastewater treatment and biomass production. However, bacteria associated with the algal phycosphere may act as environmental reservoirs of multidrug-resistant (MDR) phenotypes and antibiotic resistance genes (ARGs), including resistance to last-resort antibiotics such as colistin. Methods: An axenic culture of the freshwater microalga Pectinodesmus pectinatus was established using a NaClO-based cleaning protocol. Three phycosphere-associated bacterial strains (Chryseobacterium sp., Pseudomonas monteilii, and Stenotrophomonas pavanii) were isolated and identified by 16S rRNA gene analysis. Antimicrobial susceptibility testing was performed using broth microdilution against 16 antibiotics. Whole-genome sequencing of the most resistant isolate, S. pavanii, was conducted using Oxford Nanopore technology, followed by genome annotation and in silico resistome analysis using CARD, AMRFinderPlus, and ResFinder. Results: Among the three isolates, S. pavanii exhibited the broadest resistance profile, including high minimum inhibitory concentrations (MICs) to multiple β-lactams and colistin (MIC ≥ 16 μg/mL). No plasmid-borne mcr genes were detected. Instead, the genome encoded multiple chromosomal determinants potentially associated with polymyxin non-susceptibility, including lipid A and lipopolysaccharide modification pathways (e.g., arn genes and eptA), outer-membrane maintenance and LPS transport systems, multidrug efflux pumps, and regulatory elements. Integration of genomic and phenotypic data suggested that the observed colistin non-susceptibility may be associated with intrinsic chromosomal determinants inferred from whole-genome analysis. Conclusions: This study demonstrates that the P. pectinatus phycosphere can harbor multidrug-resistant (MDR) bacteria, including strains exhibiting colistin non-susceptibility potentially associated with a repertoire of intrinsic chromosomal resistance mechanisms inferred from genomic analysis. Therefore, freshwater microalgae-based systems should be considered potential environmental reservoirs contributing to the dissemination of antimicrobial resistance. Full article

Hospital wastewater represents a critical hotspot for the dissemination of antibiotic resistance genes (ARGs), serving both as an environmental reservoir and a transmission pathway for multidrug-resistant bacteria into receiving ecosystems. The intense antibiotic selective pressure within healthcare facilities promotes the emergence, persistence and amplification of resistant strains, posing substantial risks to public health and environmental integrity. This study aimed to characterize Escherichia coli (E. coli) isolates recovered from hospital wastewater effluents in multiple cities across Gabon, with emphasis on bacterial loads, antimicrobial resistance patterns and associated genetic determinants. Wastewater samples were aseptically collected from sewer outlets of eleven healthcare facilities distributed across five provinces over a 12-week period, structured into two six-week sampling campaigns to capture temporal variability. A total of 158 bacterial isolates were obtained, among which 49 were confirmed as E. coli. Mean concentrations of presumptive E. coli ranged from 7.1 × 10³ to 1.49 × 10⁹ CFU/mL, indicating substantial microbial contamination of hospital effluents. Antimicrobial susceptibility testing using the Kirby–Bauer disk diffusion method against 19 antibiotics revealed that all isolates exhibited multidrug-resistant phenotypes. Resistance rates were particularly high to β-lactams and third-generation cephalosporins, reaching 90–100% in most facilities, reflecting strong selective pressure and widespread circulation of resistance mechanisms in urban aquatic environments. In contrast, carbapenems and amikacin remained comparatively effective, with resistance levels below 40%, suggesting partial preservation of last-resort therapeutic options. The values of the Multiple Antibiotic Resistance Index (MARI) ranged from 0.21 to 0.84, indicating selection pressure on different classes of antibiotics. Phylogenetic analysis showed a predominance of phylogroup A, traditionally considered commensal but increasingly associated with the spread of resistance. Groups B2, D/E and F proved to be the most resistant. These groups showed marked resistance to first-line antibiotics. The blaCTX-M-1 was the most prevalent resistance determinant (66.6%), occurring twice as frequently as blaSHV (33.3%), a finding that confirms the significant circulation of extended-spectrum β-lactamase-producing E. coli. Overall, these findings highlight hospital wastewater as a major reservoir and dissemination source of multidrug-resistant E. coli, underscoring the urgent need for improved wastewater treatment, strengthened antimicrobial stewardship and integrated One Health-based surveillance strategies. Full article

Antimicrobial resistance (AMR) represents a global health crisis, driven largely by the mobility of resistance determinants through mobile genetic elements (MGEs). These include plasmids, integrons, insertion sequences, transposons, integrative and conjugative elements (ICEs), and prophages, which together facilitate horizontal gene transfer (HGT) across bacterial species and ecosystems. This review aims to provide a comprehensive synthesis of current knowledge on the types, mechanisms, ecological drivers, and impacts of MGEs in the dissemination of antibiotic resistance genes (ARGs). Methods involved critical evaluation of recent genomic, epidemiological, and ecological studies, alongside case studies of clinically significant resistance outbreaks. Findings highlight how MGEs function as hubs for ARG capture, recombination, and stabilization, enabling the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) pathogens. We also explored their interactions with ecological pressures such as antibiotics, heavy metals, and biocides, as well as their role in One Health transmission pathways. The significance of this study lies in linking molecular insights with applied strategies, including genomic surveillance, MGE-targeted inhibitors, phage therapy, and CRISPR-based interventions. Understanding MGEs is essential for designing effective interventions to mitigate AMR and protect global health. Full article

Several species of the genus Acinetobacter are nosocomial pathogens with a well-documented ability to acquire resistance to multiple antibiotics. Although Acinetobacter is one of the most abundant genera in meat processing environments, data on this genus outside of clinical environments remains limited. The objective of this study was to ascertain the prevalence, diversity and antimicrobial resistance profile of Acinetobacter spp. in 200 samples collected from food contact surfaces, non-food contact surfaces, carcasses and final meat cuts across five pork, chicken and beef processing facilities, each comprising physically connected slaughterhouses and meat processing plants. Acinetobacter spp. were detected in 80% (95% CI = 71–87%) and 70% (95% CI = 60–79%) of samples from slaughterhouses and processing plants, respectively. The facilities harboured a wide diversity of Acinetobacter species, with 27 different species identified. Acinetobacter baumannii was the species most frequently detected. Whole-genome sequencing of 18 Acinetobacter spp. isolates revealed the presence of ARGs conferring resistance to beta-lactams, tetracyclines and aminoglycosides, and disclosed phylogenetic relationships with isolates from fresh meat. Phenotypic resistance to beta-lactams, fluoroquinolones, aminoglycosides, folate pathway inhibitors and/or tetracyclines was observed in 77.8% of the sequenced isolates, with 44.4% classified as multidrug-resistant. These findings identify meat processing environments as an important reservoir of Acinetobacter spp. and highlight the need for further investigation to prevent the dissemination of antimicrobial-resistant strains. Full article

Antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs) have emerged as critical environmental contaminants posing serious ecological and public health concerns. The widespread occurrence and proliferation of ARB and ARGs in wastewater treatment plants (WWTPs) and reclaimed wastewater (RWW) used for irrigation represent major pathways for their dissemination into the environment. Current knowledge indicates that ARGs from the environmental resistome can be transferred among diverse microbial communities, including clinically relevant human pathogens. Numerous studies have also linked the expansion of the environmental resistome to anthropogenic activities. Therefore, preventing and mitigating the spread of antibiotic resistance in the environment requires a deeper understanding of how resistance genes evolve, transfer, and persist across ecological compartments. This review synthesizes the current state of knowledge on the occurrence, prevalence, and detection of antibiotics, ARB, and ARGs in various environmental matrices, providing essential insights for developing preventive strategies and promoting the sustainable management of ecosystems. Full article

Background: Multidrug-resistant (MDR) Escherichia coli in intensive pig production represents a persistent animal health and One Health concern. Here, we integrated quantitative phenotypic susceptibility data with whole-genome sequencing (WGS) to characterize the resistome and its inferred genomic context (chromosomal vs. plasmid-predicted contigs and mobile genetic element (MGE)-proximal regions) in swine-associated MDR E. coli from Hungary. Methods: A total of 203 E. coli isolates from large-scale pig farms were tested by broth microdilution. Based on resistance-oriented screening from an extended-spectrum β-lactamase (ESBL)-screen-positive pool, 116 isolates were subjected to whole-genome sequencing (WGS) as a resistance-enriched subset. Resistance determinants were annotated using the Comprehensive Antibiotic Resistance Database (CARD). Results: Resistance-oriented screening indicated frequent β-lactamase activity and ESBL screening positivity (110/203 and 127/203 isolates, respectively), consistent with strong antimicrobial selection pressure in the source population. Across the full phenotypic panel, 78/203 isolates (38.4%) met the MDR definition (non-susceptible to ≥3 antimicrobial classes), with marked between-farm variation (p < 0.001) but no age-group effect (p = 0.75). Non-β-lactam minimum inhibitory concentration (MIC) distributions showed pronounced, site-dependent high-MIC “tails”, most notably for tetracyclines, trimethoprim–sulfamethoxazole, fluoroquinolones, and colistin. In the WGS cohort (n = 116), we detected 82 distinct resistance determinants (5433 total occurrences), featuring a conserved chromosomal backbone enriched for intrinsic multidrug resistance components and lipid A modification pathways, alongside common plasmid- and MGE-associated acquired ARG modules involving tetracycline (tetA/tetB), sulfonamide/trimethoprim (sul/dfrA), aminoglycoside-modifying enzymes, and phenicol determinants (floR/cat). High-priority mobile determinants were rare but present, including mcr-1 (3/116; plasmid-associated) and plasmid-mediated quinolone resistance qnrB5 (2/116). Conclusions: Importantly, mobility/context inferences are restricted to this ESBL-screen-enriched WGS subset. Swine-associated E. coli from Hungarian large-scale farms harbors complex resistance architectures shaped by co-selection of mobile ARG modules on top of a pervasive chromosomal resistance backbone. Mobility-aware surveillance and stewardship are warranted to mitigate dissemination risks at the animal–environment–human interface. Full article

Background/Objectives: Antimicrobial agents have revolutionized disease management in humans and animals; however, their misuse and overuse have accelerated the emergence and spread of antimicrobial resistance (AMR) and antimicrobial resistance genes (ARGs). Dairy farms are recognized as potential hotspots for ARG dissemination, particularly through Escherichia coli, which acts as a reservoir and vector of ARGs, enabling their horizontal transfer via plasmids and other mobile genetic elements. This study aimed to characterize the genomic diversity, ARG profiles, plasmid content, and phylogenetic relationships of E. coli isolated from dairy farm environments and milk using whole-genome sequencing. Methods: A total of 31 E. coli isolates recovered from soil, effluent, cow dung, and milk samples underwent deoxyribonucleic acid extraction, library preparation, and sequencing on the Illumina MiSeq platform, followed by comprehensive bioinformatic analysis. Results: The E. coli isolates exhibited 20 distinct sequence types, including one novel sequence type. Plasmids were detected in 71% of the isolates, with the IncF plasmid family being the most predominant. Furthermore, 12 ARG groups were identified, with β-lactam resistance genes detected in 67.7% of isolates. Notably, blaCTX-M genes were identified in all phenotypically confirmed extended-spectrum β-lactamase-producing isolates. Additional ARGs, including those conferring resistance to tetracyclines (tet(A), tetX4), quinolones (qnrS1), aminoglycosides (aph, aad, ant), and folate pathway inhibitors (dfr and sul), were widely distributed throughout the samples. Phylogenetic analysis revealed clustering of isolates from different sample types, particularly among ST58 isolates, suggesting cross-environmental transmission. Conclusions: This study demonstrates that E. coli from dairy farm environments harbor diverse ARGs and plasmids, confirming their role as reservoirs of AMR. These findings underscore the importance of prudent antimicrobial use, routine genomic surveillance, and enhanced biosecurity measures to limit cross-environmental transmission. Full article

The expansion of tropical specialty livestock farming raises urgent concerns about airborne pathogen and antibiotic resistance dissemination. Ostrich farming, characterized by high-density stocking and feed exposure, yet their microbial ecology remain poorly characterized. This study analyzed 48 bioaerosols samples from an ostrich farm in Hainan, China, across dry and rainy seasons using 16S rRNA sequencing and metagenomics. The bacterial community were dominated by Firmicutes, Proteobacteria, and Actinobacteria, followed by Staphylococcus, Bacillus, and Acinetobacter as predominant genera, with particle size significantly shaping their structure. Large particles (>7.0 μm) carried higher species richness, while medium particles (2.1–3.3 μm) exhibited the highest diversity and evenness. Notably, small particles (0.65–1.1 μm), which can penetrate deep into the lungs, were enriched with Brevibacillus and Corynebacterium. Metagenomic analysis identified 638 antibiotic resistance genes (ARGs), dominated by efflux pump-associated determinants. The detection of clinically relevant ARGs (e.g., mcr-1 and bla_TEM) reflects the genetic potential of the airborne resistome, rather than confirmed resistance phenotypes or active horizontal gene transfer. Functional analysis revealed a strong potential for organic matter degradation, driven by abundant carbohydrate-active enzymes (CAZymes) and their corresponding CAZyme genes, as well as a nitrogen cycle dominated by assimilation and reduction pathways, while genes for nitrogen fixation and nitrification were absent. Our findings demonstrate that ostrich farming enhanced airborne microbial diversity and functional potential, facilitating the ARG dissemination and nitrogen transformation. This study provides critical insights into the ecological and health risks of bioaerosols in tropical livestock farms, informing environmental monitoring and risk management strategies. Full article

Antimicrobial resistance (AMR) constitutes one of the most severe and pressing threats to global public health, food security, and environmental integrity. This review synthesizes current evidence across interconnected One Health domains—humans, animals, food, and the environment—to delineate the scope, mechanisms, and drivers of AMR transmission. Our analysis reveals three principal findings. First, the scope of AMR is alarmingly extensive, with antibiotic-resistant bacteria (ARB) and genes (ARGs) now pervasive across all four ecological compartments, transcending traditional clinical boundaries. Second, this widespread distribution is critically facilitated by horizontal gene transfer mechanisms, particularly via mobile genetic elements such as plasmids, which enable ARGs to disseminate rapidly between diverse bacterial populations across different ecosystems. Third, we identify multiple interconnected drivers that actively promote this cross-ecosystem spread, encompassing both evolutionary and transmission drivers. By characterizing these critical transmission pathways and underlying drivers, this review provides an integrated framework to identify critical transmission risks and inform integrated strategies for mitigating antimicrobial resistance across One Health domains. Full article

The convergence of global plastic pollution and antimicrobial resistance crises has intensified concerns about the role of microplastics (MPs) in disseminating antibiotic resistance genes (ARGs) in marine environments. This review synthesizes the mechanistic pathways through which MPs act as vectors for ARG propagation, supported by a bibliometric analysis of 144 studies retrieved from Scopus. MPs possess distinct physicochemical properties such as nanoplastic formation, polymer-specific sorption, weathering-induced oxidation, and additive leachate release that facilitate microbial colonization and biofilm formation. These plastisphere biofilms, enriched with mobile genetic elements including integrons, transposons, and plasmids, promote ARG transfer via conjugation, transformation, and transduction. Environmental modulators like salinity, oxygen, nutrients, pH, UV exposure, and reactive oxygen species further accelerate horizontal gene transfer, while co-selection pressures from heavy metals and antibiotics amplify resistance dissemination. Bibliometric mapping reveals a sharp rise in publications since 2018, with China leading contributions and major research themes centered on horizontal gene transfer, metagenomics, nanoplastics, and biofilm-mediated resistome evolution. Overall, marine MPs substantially intensify ARG spread through complex microbe–plastic–pollutant interactions, posing significant ecological and public health risks. Addressing current gaps, such as limited field validation, underexplored nanoplastic mechanisms, geographic bias, and lack of standardized monitoring, requires harmonized surveillance, omics integration, pollutant mixture modeling, and One Health-based risk assessment to inform global policy interventions. Full article

Background/Objectives: Antimicrobial resistance (AMR) in wastewater represents a valuable reservoir of information for wastewater-based epidemiology (WBE) and a major environmental and public health concern, as wastewater treatment plants (WWTPs) are recognized hotspots for the accumulation and dissemination of antimicrobial resistance genes (ARGs). Within the One Health framework, and to better understand the contribution to AMR spread and the potential of metagenomic surveillance, this study aimed to characterize the taxonomic, functional, and resistome profiles of three WWTPs in Sicily, specifically those located in Catania, Giarre, and Syracuse. Methods: Sixty-nine composite influent samples were collected between February 2022 and December 2023. Shotgun metagenomic sequencing was performed on the Illumina NovaSeq platform. Bioinformatic analyses were conducted to assess microbial community composition, functional pathways, and ARG prevalence across sites. Results: Dominant genera included Aliarcobacter, Bacteroides, and Acinetobacter. Site-specific taxonomic variations reflected differences in local microbial ecology. Functional profiling revealed enrichment in membrane-associated, ribosomal, and energy metabolism pathways, consistent with the expected functional redundancy of wastewater microbiomes. Resistome analysis detected a diverse and ubiquitous array of ARGs, dominated by β-lactam and macrolide resistance genes, followed by aminoglycoside, sulphonamide, and tetracycline classes. Conclusions: These findings highlight urban wastewater as a relevant reservoir and dissemination route for AMR and support the integration of metagenomic approaches into wastewater surveillance programs. By providing region-specific, integrated taxonomic, functional, and resistome data from Sicilian WWTPs, this study contributes to the growing body of evidence supporting WBE as a valuable tool for AMR monitoring and One Health-oriented risk assessment. Full article

Background: The efficiency of vermicomposting in reducing antibiotic resistance genes (ARGs) in dairy manure may be compromised by co-pollutants like arsenic (As) and microplastics. Specifically, plasmids serving as carriers and vectors of ARGs were largely distributed in this process. However, the impact of As and microplastics on plasmids carrying ARGs during vermicomposting is largely unknown. Methods: This study utilized a controlled experimental design and applied plasmid metagenomics to investigate the individual and combined effects of As and polyethylene terephthalate (PET) microplastics on plasmid-mediated ARG dynamics during vermicomposting. Results: We found that vermicomposting alone mainly enriched non-mobilizable plasmids, while PET microplastics selectively promoted conjugative and mobilizable plasmids, whereas As significantly increased all plasmid types. Moreover, both PET or As alone and combined exposure (PET and As) increased total ARG abundance, with their combination inducing synergistic ARG enrichment despite unchanged total plasmid abundance. Furthermore, co-occurrence network analysis combined with ARGs/plasmid ratio assessments demonstrated that As influences ARGs through co-selective pressure by enriching ARGs co-localized with As resistance genes (e.g., the ars operon) on plasmids while simultaneously promoting horizontal gene transfer (HGT) via activation of oxidative stress and SOS response pathways. In contrast, PET primarily facilitates ARG dissemination through a “metabolism-resistance” coupling strategy by enriching colonizing bacteria with PET-degrading capacity. Their co-exposure formed As-enrichment hotspots on PET microplastic surfaces, functioning as a “super-mixer” that selectively screened for superbugs carrying potent resistance mechanisms (e.g., bla_OXA-50 and mdtB/mdtE). Conclusions: This study provides the first plasmidome-level evidence of synergistic ARG propagation by As and PET microplastics during vermicomposting, highlighting mobile genetic elements’ critical role in co-pollutant risk assessments. Full article

Antimicrobial resistance (AMR), mostly resulting from the widespread use of antimicrobials in healthcare, veterinary, and agriculture, poses a significant challenge to global health. Healthcare facilities are hotspots of AMR due to high antibiotic consumption and the presence of highly susceptible populations. Moreover, there may be a dynamic exchange in AMR between healthcare infrastructures, human populations, animals, and the environment. To address these challenges, this review presents a One Health perspective, emphasizing the complex interconnections among many ecosystems. Furthermore, the development and dissemination of AMR in the healthcare environment, via surfaces and hands, have been critically investigated. Some of the neglected aspects that contribute to AMR, such as ventilation and wastewater, have also been addressed. The natural environment plays a crucial role as a reservoir for antimicrobial resistance genes (ARGs). The expected increase in AMR in the coming years will not only pose a challenge to public health but also to food security and environmental health. Hospitals should install advanced systems for treating wastewater to reduce the discharge of antimicrobials. Hospitals should also combine full water, sanitation, and hygiene (WASH) protocols with infection prevention and control (IPC) methods. These efforts are aimed at preventing infections and protecting public health and the environment. Other measures include advancing research to understand transmission pathways, increasing surveillance, reducing contamination in healthcare settings, implementing national plans for stewardship, and globally sharing resources and targets to reduce AMR. Full article