Search Results (140)

Background/Objectives: Staphylococcus aureus is a multifaceted pathogen responsible for diseases in humans and in several animal species, including dairy cows. This study aimed to characterize and compare the genetic diversity, lineage distribution, and antimicrobial resistance profiles of S. aureus isolates from bovine milk with human-derived reference genomes to investigate host adaptation and inter-species transmission. Methods: Genomic analyses were performed on S. aureus isolates from quarter milk samples of dairy cows together with human-derived sequences from public databases. Whole-genome sequencing and multi-locus sequence typing (MLST) were used to determine sequence type (ST) distribution, and the presence of key antibiotic resistance genes and mobile genetic elements (MGEs) was assessed. Comparative genomics was applied to evaluate gene content, phylogenetic relationships, and lineage–host associations. Results: The dataset encompassed bovine-adapted lineages (CC97, CC133, CC151) and human-associated lineages (CC1, CC5, CC8, CC30, CC45), as well as livestock-associated ST398 in bovine samples and human-adapted ST5 and ST6 in animals. ST8 was the only ST shared between animal and human isolates and showed differing resistance profiles, with animal ST8 carrying resistance determinants absent from human ST8. Bovine-adapted strains were characterized by recurrent loss of human-associated virulence genes and acquisition of bovine-associated mobile genetic elements, and blaZ and mecA were rarely detected in bovine-adapted CC97 but were frequently present in human CC5 and CC8. Overall, animal isolates carried fewer resistance genes than human isolates. Conclusions: S. aureus from dairy cows and humans displayed substantial genetic diversity, with evidence of host-associated lineages and dynamic changes in gene and mobile element content. These findings support the need for integrated One Health surveillance to track shared and host-adapted lineages and their antibiotic resistance determinants. Full article

Background: Stenotrophomonas maltophilia is an increasingly important multidrug-resistant opportunistic pathogen frequently isolated from clinical, environmental, and plant-associated niches. Despite its medical relevance, the global population structure, species-complex boundaries, and genomic determinants of antimicrobial resistance (AMR) and ecological adaptation remain poorly resolved, partly due to inconsistent annotations and fragmented genomic datasets. Methods: Approximately 2400 genome assemblies annotated as Stenotrophomonas maltophilia were available in the NCBI Assembly database at the time of query. After pre-download filtering to exclude metagenome-assembled genomes and atypical lineages, 1750 isolate genomes were retrieved and subjected to stringent quality control (completeness ≥90%, contamination ≤5%, ≤500 contigs, N50 ≥ 10 kb, and ≤1% ambiguous bases), yielding a final curated dataset of 1518 high-quality genomes used for downstream analyses. Genomes were assessed using CheckM, annotated with Prokka, and compared using average nucleotide identity (ANI), pan-genome analysis, core-genome phylogenomics, and functional annotation. AMR genes, mobile genetic elements (MGEs), and metadata (source, host, and geographic origin) were integrated to assess lineage-specific genomic features and ecological distributions. Results: ANI-based clustering resolved the S. maltophilia complex into multiple distinct genomospecies and revealed extensive misidentification of publicly deposited genomes. The pan-genome was highly open, reflecting strong genomic plasticity driven by accessory gene acquisition. Core-genome phylogeny resolved well-supported clades associated with clinical, environmental, and plant-related niches. Resistome profiling showed widespread intrinsic MDR determinants, with certain lineages enriched for efflux pumps, β-lactamases, and trimethoprim–sulfamethoxazole resistance markers. MGE analysis identified lineage-specific integrative conjugative elements, prophages, and transposases that correlated with source and geographic distribution. Conclusions: This large-scale analysis provides the most comprehensive genomic overview of the S. maltophilia complex to date. Our findings clarify species boundaries, highlight substantial taxonomic misannotation in public databases, and reveal lineage-specific AMR and mobilome patterns linked to ecological and clinical origins. The curated dataset and evolutionary insights generated here establish a foundation for global genomic surveillance, epidemiological tracking, and future studies on the evolution of antimicrobial resistance in S. maltophilia. Full article

Karstic regions are globally distributed, and the soil-forming parent rocks and their weathering process primarily cause elevated geochemical heavy metal (HM) accumulation in karst soils. However, the patterns of HMs, the genes related to resistance, and their interactions in karstic soils developed from different parent materials remain unexplored. In this study, 36 field karst soil samples originating from two parent materials were collected, including 19 samples from the residues of the weathering and leaching of carbonate rocks (Car) and 17 samples from Quaternary sediments (Qua). In the Car soils, the levels of As, Cd, Cr, Zn, Cu, Ni, and Pb exceeded the risk screening values for soil contamination of agricultural land set by the Chinese standard GB15618-2018 by 100%, 100%, 94.11%, 64.71%, 64.71%, 47.06%, and 41.18%, respectively, while only 11.76% of As in Qua soils exceeded the risk screening values. The proportion of metal resistance genes (MRGs) and antibiotic resistance genes (ARGs) in Car soils was significantly higher than that in Qua soils. However, HM content had a significantly positive correlation with Nemerow integrated pollution index (NIPI), individual HM-related genes, MRGs, ARGs, and mobile genetic elements (MGEs) in Qua soils, respectively. Although the corresponding correlation was positive in the Car soils, it was not statistically significant. Results demonstrated that microbial activity was more crucial for the accumulation of HMs in Qua soils compared with Car soils. Meanwhile, our in-depth research also provides new perspectives to establish a more rational ecological assessment for the elevated HMs by identifying applicable and valid biomarkers from functional genes, which is vital in contamination monitoring, prevention, and standard establishment in agricultural soils of karst regions. Full article

The improper use of antibiotics accelerates the emergence of resistance via environmental selection pressures, jeopardizing public health and ecosystems by promoting the worldwide dissemination of antibiotic resistance genes (ARGs). Reservoirs, as crucial water supplies, have been recognized as primary reservoirs of ARGs, particularly those that originate from the Yellow River, necessitating further investigation. This study analyzed 9 ARGs, 3 mobile genetic elements (MGEs), 16 antibiotics, and 10 heavy metals in water/sediments from three reservoirs originating from the Yellow River in Henan Province, China. The findings indicated that antibiotic concentrations in water exceeded those in sediment, with quinolones detected at 100% frequency (5.47–116.03 ng/L) and enrofloxacin predominating (3.36–107.71 ng/L). Redundancy analysis revealed that MGEs exert greater control over ARG dissemination than antibiotics, with intI1 showing strong positive correlations with sul1 (p < 0.05). Conversely, heavy metals (Zn, As, Cd) suppress ARG proliferation through negative selection pressures. A network study indicated Mycobacterium, Pseudarthrobacter, and Massilia as critical hosts for ermB, tetA, and qnrA, respectively. Of the three reservoirs, Jian’gang Reservoir, driven by synergistic effects of unique microbial ecology, water self-purification capacity, and flow dynamics, exhibited the best removal effectiveness of ARGs from input to outflow, with 71.75% in the water and 97.91% in the sediment. These findings provide critical insights into the prevalence, migration, and self-purification processes of ARGs in reservoirs originating from the Yellow River, integrating environmental factors and microbial data to clarify the complex dynamics affecting ARG behavior and inform targeted pollution control strategies. Full article

The overuse of antibiotics has led to the dissemination of antibiotic resistance genes (ARGs) in agricultural ecosystems, posing a threat to food safety. While current research on ARG transfer in soil–crop systems mainly concerns raw-consumed vegetables like lettuce, its impact on staple crops remains insufficiently studied. This study investigates how organic fertilizer affects ARG dissemination in the soil–millet system. Four fertilization treatments were established: no fertilization (CK), chemical fertilizer only (F), chemical fertilizer combined with manure (FM1), and chemical fertilizer combined with double amount of manure (FM2). Samples were collected from millet rhizosphere soil, roots, stems, leaves, and grains. High-throughput quantitative PCR was employed to investigate the transfer and dissemination of ARGs across the soil–millet system. Results showed that a total of 130 ARGs and 13 mobile genetic elements (MGEs), belonging to 17 gene families, were detected across all samples. The number of unique ARGs was higher in treatments FM1 and FM2 with manure. The accumulated absolute abundances of ARGs, MGEs and gene families all showed an order of FM1 > CK > FM2 > F. Pearson correlation analysis showed a close correlation among ARGs and MGEs. Although organic fertilizer application increased the absolute abundance of ARG-related genes in the rhizosphere soil and millet tissues, posing a potential threat to food safety, the rational strategy employed in the FM1 treatment effectively reduced ARG accumulation in millet leaves and grains. Therefore, this optimized application rate is recommended for millet production. Full article

The genus Kocuria includes Gram-positive and environmentally versatile bacteria, which are of biotechnological interest due to their ability to synthesize secondary metabolites. In this study, the genome of Kocuria sp. KH4, isolated from alkaline mine tailings (southeastern Mexico), was sequenced and analyzed to determine its taxonomic affiliation and explore its metabolic and adaptive potential. The assembled genome showed a size of 3.89 Mb, a GC content of 73.2%, and 3609 coding genes. Phylogenomic analyses and genomic relationship indices (ANI, AAI, and dDDH) confirmed that strain KH4 represents a novel genomospecies within the genus Kocuria. Functional analysis revealed broad metabolic diversity, with genes associated with the transport and metabolism of amino acids, carbohydrates, and inorganic ions. A total of 165 genes linked to metal resistance and homeostasis mechanisms were identified, including ABC-type transport systems and ATPases, as well as specific genes for Fe, Ni, Zn, Cu, As, and Hg. Forty-eight genomic islands were also identified, encoding a wide variety of functions and mobile genetic elements (MGEs). Furthermore, six biosynthetic gene clusters (BGCs) involved in the production of nonribosomal peptides, type III polyketides, terpenes, and siderophores were detected, suggesting a remarkable potential for the synthesis of bioactive compounds. Taken together, the results highlight this strain as a promising source of secondary metabolites with potential applications in environmental, pharmaceutical, and industrial biotechnology, underscoring the importance of Kocuria genomes as natural reservoirs of new biosynthetic pathways. Full article

This study investigated the molecular epidemiology, virulence, antimicrobial resistance, and mobile genetic elements (MGEs) of Salmonella enterica serovar I 4,[5],12:i:- isolates collected in Jeollanam-do, South Korea, between 2021 and 2023. A total of 135 isolates were tested for antimicrobial susceptibility and 14 virulence-associated genes were screened by PCR. Pulsed-field gel electrophoresis (PFGE) assessed clonal relatedness, and whole-genome sequencing (WGS) enabled multilocus sequence typing (MLST), core genome MLST (cgMLST), SNP phylogeny, resistance gene detection, and MGE analysis. Nine virulence profiles (VP1–VP9) were identified. VP1 (74.1%) was strongly associated with multidrug resistance (MDR), while VP2 (14.8%), which carried plasmid-encoded spv genes, remained largely susceptible. Overall, 83.7% of isolates were resistant to at least one antimicrobial, and 65.2% were MDR, with ampicillin and tetracycline consistently forming the backbone of MDR phenotypes. PFGE revealed high genetic diversity, with 72 pulsotypes, yet certain clones (e.g., SMOX01.006, SMOX01.012) were widely distributed and corresponded to VP2 isolates. WGS confirmed two dominant sequence types, ST34 (n = 24) and ST19 (n = 20), with SNP phylogeny showing VP1 isolates mainly clustered with ST34 and VP2 with ST19. Genotype–phenotype concordance showed strong agreement for most antimicrobials, except cefoxitin, ciprofloxacin, amikacin, and trimethoprim/sulfamethoxazole. MGE analysis revealed that tet(B) was consistently associated with ISVsa5, while ISEc59 was linked to multiple resistance genes, though only aac(3)-IV was phenotypically expressed. These findings demonstrate that MDR and virulence gene composition were closely associated with clonal clustering and that MGEs may contribute to resistance gene expression. This study provides a basis for understanding the dissemination of resistant and virulent Salmonella in the region and underscores the need for continuous genomic surveillance. Full article

Antibiotic resistance genes (ARGs) and microbial communities in pig and cow dung from rural China were systematically profiled using high-throughput quantitative PCR arrays and 16S rDNA amplicon sequencing to assess their environmental dissemination and public health risks. The abundance and diversity of ARGs were markedly higher in pig dung than in cow dung. A total of 56 ARGs were enriched in pig dung, including β-lactamase genes (blaCMY, blaCTX-M) and macrolide resistance genes (ermB, ermF), along with several genes related to aminoglycoside and macrolide–lincosamide–streptogramin B resistance. In contrast, only eight ARGs were enriched in cow dung. Microbial community analysis revealed that cow dung was dominated by UCG-005, UCG-010, Methanocorpusculum, and Fibrobacter, taxa typically associated with ruminant digestion. In pig dung, Ignatzschineria, Lactobacillus, Pseudomonas, Streptococcus, Treponema, and conditional pathogens such as Escherichia coli and Leptospira were significantly enriched, indicating higher pathogen-related risks. Functional prediction identified 26 KEGG level-2 and 136 level-3 pathways, showing stronger xenobiotic degradation and amino acid metabolism in pig dung, whereas cow dung was enriched in energy metabolism and chemotaxis pathways. Moreover, the higher abundance of mobile genetic elements (e.g., intI1 and IS613) in pig dung suggests a greater potential for horizontal ARG transfer. Integrating ARG, microbial, and pathogen data reveals that pig dung acts as a composite source of “ARG–pathogen” contamination with enhanced transmission potential. These findings provide localized, data-driven evidence for developing safer livestock waste management practices, such as composting and biogas utilization, and contribute to antibiotic resistance mitigation strategies in rural China. Full article

Probiotics are widely used as feed additives in livestock production, yet the overall safety of commercially available veterinary probiotics remains insufficiently assessed. In this study, 33 probiotic products marketed in Northern China were systematically evaluated with respect to strain composition, label accuracy, antimicrobial resistance, and the diversity of resistance genes. A total of 32 Bacillus spp. were isolated, many of which showed resistance to multiple antibiotics. Labeling inaccuracies were prevalent: none of the products specified strain names and numbers, 33% (11/33) failed to report viable bacterial counts, 9% (3/33) lacked their claimed key ingredients, and 21% (7/33) contained isolated strains that did not match the label. High-throughput quantitative PCR (HT-qPCR) analysis further revealed that all 27 tested products harbored abundant antibiotic resistance genes (ARGs), with 241 ARGs and seven mobile genetic elements (MGEs) detected. The ARGs were primarily associated with tetracycline, aminoglycosides, β-lactams, and macrolide–lincosamide–streptomycin B (MLSB) antibiotics, and co-occurrence analysis showed a strong positive correlation between ARG and MGE abundance, with Clostridium and Enterococcus identified as potential hosts. These findings underscore significant quality and safety deficiencies in veterinary probiotics and highlight potential risks to animal, human, and environmental health, emphasizing the relevance of a One Health perspective in probiotic evaluation and regulation. Full article

The emergence and global dissemination of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-E. coli) represent a major public health concern. However, the characterization and capacity for horizontal gene transfer (HGT) of ESBL-E. coli in captive black bears remain substantially understudied. In the present study, 19 ESBL-E. coli strains were successfully identified (13.38%, 19/142). A total of 11 sequence types (STs) were identified from 19 ESBL-E. coli strains using MLST. This included eight known types (ST10, ST2690, ST208, ST695, ST4160, ST540, ST3865 and ST2792) and three new STs. Antimicrobial susceptibility testing demonstrated that all 19 ESBL-E. coli exhibited high resistance to KZ (100.00%), CRO (78.95%), and CTX (73.68%). Polymerase chain reaction (PCR) screening for 14 β-lactam antibiotic resistance genes (ARGs) and their variants revealed that bla_CTX-M was the most prevalent, followed by bla_SHV, bla_TEM, and bla_DHA. Furthermore, eight β-lactamase variants were detected, including five bla_CTX-M variants (bla_CTX-M-15, bla_CTX-M-3, bla_CTX-M-14, bla_CTX-M-55, and bla_CTX-M-27) and one variant each of bla_SHV-1, bla_TEM-1, and bla_DHA-14. Conjugation assays revealed that eight ESBL-E. coli strains were capable of conjugative transfer. Five plasmid types (IncFII, IncW, IncFrepB, IncY, and IncHI1) and three mobile genetic elements (MGEs) (IS26, ISEcp1, and trbC) were identified as co-transferred with bla_CTX-M. ESBL-E. coli poses a potential threat to captive black bears and may lead to further transmission. Consequently, the implementation of continuous surveillance and targeted interventions is imperative to prevent the transmission of ESBL-E. coli. Full article

The phenotypic resistance of 56 Enterococcus faecalis isolates from Eurasian griffon vultures was subjected to surveillance testing with the microdilution method using a standardized panel of antimicrobials. Isolates were also characterized by MLST. Additionally, the genome of 19 isolates with phenotypic resistance to linezolid, ciprofloxacin, chloramphenicol and/or high-level resistance to gentamicin were sequenced to determine their antimicrobial resistance (ARGs) and virulence-associated genes and to identify mobile genetic elements (MGEs). Most isolates (82.1%) exhibited non-wild-type phenotypes to six antimicrobial agents, and multidrug resistance (MDR) was detected in 34% of the isolates. Most MDR isolates (53%) belonged to ST16, ST116 and ST35. ARGs were localized on the chromosome as well as on various MGEs previously reported in human, food and livestock isolates, suggesting that vultures may acquire antibiotic-resistant bacteria (ARBs) and/or ARGs as a consequence of anthropogenic pollution. Overall, 22 virulence-associated genes encoding cell surface and secreted factors were identified, some of which were located on MGEs that also carried ARGs. The significant proportion of E. faecalis isolates recovered from vultures that exhibited MDR phenotypes and harbored MGEs carrying ARGs and virulence-associated genes is cause for concern, since vultures may act as spreaders of these genes to the environment, domestic animals and humans. Full article

Stenotrophomonas maltophilia (S. maltophilia) is a multidrug-resistant opportunistic pathogen. There are an increasing number of case reports on S. maltophilia infections in recent years, and the species is becoming a public health concern. Many studies have focused on profiling and pangenome of the species, particularly on their antibiotic resistance and virulence genes. However, there is a lack of studies on mobile genetic elements (MGEs), a subset of pangenome that significantly contributes to the diversity, stability, and plasticity of a population. In this study, 20 genomes of S. maltophilia were downloaded from the NCBI Genome database. The genomes were subjected to profiling of MGEs, their impact on the population structures, and the evaluation of evolutionary trends of the core genomes. The cataloguing of MGEs indicated active horizontal gene transfer events in the S. maltophilia’s population. Multiple virulence and drug resistance genes were predicted within and outside of the MGEs. We observed multiple chromosomal rearrangements in the genomes, most likely caused by MGEs, affecting up to approximately 50% of a single genome sequence. A high number of linkage disequilibrium sites were also predicted in the core genomes. This study provides insights into stability in the core and plasticity in the accessory regions in the S. maltophilia population. Full article

The propagation of antibiotic resistance genes (ARGs) in aquatic environments poses a significant threat to global health. This study compared sediment resistome profiles in river crab (Eriocheir sinensis) polyculture systems with and without stone moroko (Pseudorasbora parva). The results showed that, compared to the control group (MC group), the sediment from the polyculture system containing stone moroko (PC group) exhibited significant reductions in the total abundances of ARGs, metal resistance genes (MRGs), biocide resistance genes (BRGs), and mobile genetic elements (MGEs). Crucially, the total abundance and composition of MGEs in pond sediment were substantially correlated with ARGs, MRGs, and BRGs, respectively. Co-occurrence network analysis revealed that there was only one edge between ARGs and MGEs in the PC group, whereas the MC group had eight edges. Additionally, the proportion of mobile ARGs in the PC group was significantly lower than that in the MC group. Alterations in resistome profiles were markedly associated with decreased levels of total carbon (TC) and phosphate in the sediment. All of the findings demonstrated that the introduction of stone moroko in the river crab polyculture system effectively mitigated the sediment resistome primarily by altering environmental factors and suppressing MGEs, thereby disrupting the horizontal transfer network of resistance genes. This study highlights the potential of leveraging aquatic biota as a novel biological strategy for the in situ management of environmental antimicrobial resistance. Full article

Extended-spectrum β-lactamases (ESBLs) and plasmid-mediated AmpC (pAmpC) β-lactamases represent a threat for public health. Their dissemination is often mediated by mobile genetic elements (MGEs), but plasmid identification and characterization could be hindered by sequencing limitations. Hybrid assembly may overcome these barriers. Eight ESBL/pAmpC-producing E. coli isolates from broilers were sequenced using Illumina (short-read) and Oxford Nanopore MinION (long-read). Assemblies were generated individually and using a hybrid approach. Plasmids were typed, annotated, and screened for antimicrobial resistance genes (ARGs), MGEs, and virulence factors. Short-read assemblies were highly fragmented, while long reads improved contiguity but showed typing errors. Hybrid assemblies produced the most accurate and complete plasmids, including more circularized plasmids. Long and hybrid assemblies detected IS26 associated with ESBL genes and additional virulence genes not identified by short reads. ARG profiles were consistent across methods, but structural resolution and contextualization of resistance loci were superior in hybrid assembly. Hybrid assembly integrates the strengths of short- and long-read sequencing, enabling accurate plasmid reconstruction and improved detection of resistance-associated MGEs. This approach may enhance genomic surveillance of ESBL/pAmpC plasmids and support strategies to mitigate antimicrobial resistance. Full article

The global rise of antimicrobial resistance (AMR), exacerbated by the COVID-19 pandemic, has led to a surge in infections caused by multidrug-resistant (MDR) bacteria. A key driver of this phenomenon is co-selection, where exposure to one antimicrobial promotes resistance to others via horizontal gene transfer (HGT) mediated by mobile genetic elements (MGEs). Carbapenem-resistant Enterobacteriaceae, known for their genomic plasticity, are particularly worrisome; yet genomic data from Latin America—especially Ecuador—remain scarce. This study investigated four carbapenem-resistant clinical isolates (two Klebsiella pneumoniae ST1440 and two Serratia marcescens) from tracheal aspirates of three ICU patients during a COVID-19 outbreak at Hospital IESS Quito Sur, Ecuador. Phenotypic profiling and whole-genome sequencing were performed, followed by bioinformatic reconstruction of plasmid content. Nineteen plasmids were identified, carrying 70 resistance-related genes, including antimicrobial resistance genes (ARGs), metal resistance genes (MRGs), integrons, transposons, and insertion sequences. Hierarchical clustering revealed six distinct gene clusters, with several co-localizing ARGs and genes for resistance to disinfectants and heavy metals—suggesting strong co-selective pressure. Conjugative plasmids harboring high-risk elements such as blaKPC-2, qacE, and Tn4401 were found in multiple isolates, indicating potential interspecies dissemination. These findings emphasize the importance of plasmid-mediated resistance during the pandemic and highlight the urgent need to enhance genomic surveillance and infection control, particularly in resource-limited healthcare settings. Full article