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Genomic epidemiology of clinically critical antibiotic resistance in Salmonella enterica causing bloodstream infections across six Chinese provinces, 1994-2023.

Clinically critical antibiotic-resistant Salmonella enterica (S. enterica) causing bloodstream infections remains a public health challenge. Here, we aim to reveal the emergence and trends of clinically important antibiotic resistance in S. enterica causing bloodstream infections using 833 isolates from six Chinese provincial-level administrative areas during 1994-2023. We identified 48 serovars and 64 sequence types (STs). Overall, 8.52% of 833 isolates were resistant or had decreased susceptibility to ciprofloxacin, 4.32% and 6.84% reported resistance or decreased susceptibility to third- and fourth-generation cephalosporins (3GCs and 4GCs), 1.80% reported resistance to fosfomycin, and 2.16% reported resistance to azithromycin. Across these six regions, azithromycin and fosfomycin resistance is increasing, as is decreased susceptibility or resistance to ciprofloxacin, 3GCs, and 4GCs, especially among younger children and elderly people. Clinically prioritized antibiotic resistance also varies by region, serovar, and age group. S. Paratyphi A genotype 2.3.3 strains are mainly divided into 2 lineages distributed in Guangxi and Shanghai. Within the scope of this passive surveillance dataset, S. Typhi genotype 4.3.1.2.1 was identified as the earliest documented case among the collected isolates. Our retrospective and longitudinal genomic epidemiology study provides critical data for the formulation of treatment guidelines and policies for bloodstream infections and for the monitoring and control of antimicrobial resistance.

Humans

Genomic and food-safety evaluation of Staphylococcus chromogenes in Chinese dairy milk.

Non-aureus staphylococci and mammaliicocci (NASM) cause mastitis and may contaminate milk and dairy products. Milk samples (n&#xa0;=&#xa0;1916) from cows with subclinical or clinical mastitis (SCM and CM, respectively) were collected from 28 large-scale (> 500 lactating cows) Chinese dairy farms. Overall, 999 NASM isolates representing 19 species were identified by MALDI-TOF MS and cpn60 sequencing, with Staphylococcuschromogenes, Mammaliicoccus sciuri and Staphylococcus haemolyticus being most prevalent. Antimicrobial resistance (AMR) was determined with disc diffusion; non-susceptible to penicillin was most common (SCM, 30% and CM, 29%) whereas cefoxitin non-susceptible NASM accounted for 8-10% of isolates; among these, 12.5% carried mecA but none carried mecC. Galleria mellonella was used to assess virulence of 78 strains of S. chromogenes, a dominant species; subsequently, 32 strains, representing higher- and lower-virulence in the Galleria model, were selected for whole-genome sequencing and comparative genomics. S. chromogenes isolates from CM had higher virulence (p&#xa0;<&#xa0;0.05) than those from SCM. The 32 genomes comprised 20 sequence types, indicating high genetic diversity. No robust genomic marker of Galleria virulence phenotype was identified in this selected WGS subset. Acquired resistance genes (n&#xa0;=&#xa0;5) were detected, including a first report of fusC in S. chromogenes; the fusC-positive isolate had an elevated fusidic acid MIC (8&#xa0;mg/L). Although S. chromogenes persisted in milk at 4&#xa0;&#xb0;C, pasteurization (64&#xa0;&#xb0;C for 30&#xa0;min) reduced viable counts to below detection. This study provided new insights into the prevalence, AMR, genomic diversity, and dairy-chain relevance of milk-derived NASM, particularly S. chromogenes. However, the genomic findings were based on an intentionally selected WGS subset and should be interpreted as hypothesis-generating rather than population-representative.

Animals

Portable metagenomics for preventive surveillance and outbreak control in livestock and poultry: Pathogen detection, resistome profiling, and antimicrobial stewardship.

Conventional diagnostics for livestock and poultry outbreaks commonly rely on culture or targeted PCR panels, which may be too slow or too narrow to guide early control decisions. Portable metagenomics, particularly real-time nanopore sequencing, offers a route to broad pathogen detection, antimicrobial-resistance gene profiling, and outbreak investigation within an integrated workflow. This implementation-focused review evaluates how near-point-of-care metagenomics may support preventive veterinary medicine through earlier detection, surveillance, cohorting, biosecurity decisions, and antimicrobial stewardship. We synthesize sample-to-answer workflows for enteric and respiratory disease in food-producing animals, including sampling, nucleic-acid extraction, host depletion or target enrichment, library preparation, sequencing, bioinformatics, quality control, and interpretation. Applications in calf diarrhea, bovine respiratory disease, poultry outbreaks, mastitis, and resistome monitoring are considered alongside the central limitation that detection alone does not establish causation. Pathogen and resistance-gene signals must therefore be interpreted with clinical signs, lesions, epidemiology, controls, and confirmatory testing. We also propose a minimum reporting checklist, intended as a practical framework rather than a validated consensus standard. Portable metagenomics is not a replacement for conventional diagnostics, but appropriately validated workflows can reduce uncertainty during time-sensitive outbreaks and support more judicious antimicrobial use.

Animals

A mechanism-guided framework for prioritizing membrane-interaction anti-Vibrio peptides from peptidomics data.

A mechanism-guided framework for prioritizing membrane-interaction antimicrobial peptide candidates from proteomics-derived peptide mixtures is presented. The framework integrates conservative machine-learning-based antimicrobial peptide (AMP) screening with a literature-derived membrane-interaction plausibility (MAP) assessment and a data-driven membrane-interaction ranking function (AIPx), followed by structural visualization for interpretability. MAP encodes physicochemical characteristics commonly associated with peptide-membrane interaction and provides a graded plausibility assessment. Building upon this physicochemically interpretable framework, AIPx ranks peptides using feature weights calibrated from experimentally characterized anti-Vibrio peptides, where minimum inhibitory concentration (MIC) values are used as a coarse-grained ranking reference rather than a direct prediction target. In a peptidomics-based peptide fractionation study targeting Vibrio spp., AIPx exhibited a consistent relationship with experimentally observed antibacterial activity. Distributional analysis revealed that peptide fractions exhibiting high anti-Vibrio activity are characterized by enrichment of high-ranking peptides rather than by AMP abundance alone. By structuring AMP identification and prioritization as sequential stages, the MAP&#xa0;+&#xa0;AIPx framework enables interpretable and experimentally actionable candidate selection by reducing biologically implausible candidates. The framework facilitates species-oriented prioritization of AMP candidates, addressing a key challenge in antimicrobial peptide discovery where activity may depend on target-specific membrane characteristics. Moreover, the approach is extensible through species-specific calibration and supports interpretable, mechanism-informed prioritization in antimicrobial peptide discovery.

Proteomics

Complicated urinary tract infections: evolving definitions, clinical burden, and treatment landscape amid antimicrobial resistance.

INTRODUCTION: Complicated urinary tract infection (cUTI) is a common and heterogeneous infection associated with substantial morbidity, high healthcare utilization, and increasing antimicrobial resistance. Evolving definitions, increasing device use, and changing patient populations have altered its epidemiology and management. Marked variability in diagnostic criteria, clinical trial endpoints within and outside registrational settings, and treatment strategies complicates clinical decision-making and interpretation of therapeutic advances. AREAS COVERED: This review examines contemporary cUTI epidemiology, classification frameworks, and drivers of disease burden. It evaluates resistance trends and their therapeutic implications, alongside stewardship-based management strategies, including empiric antibiotic selection, intravenous-to-oral transition, treatment duration, and source control. Challenges in catheter-associated infection, recurrence, and regulatory endpoint design are discussed, together with the emerging role of novel agents targeting resistant Gram-negative pathogens. EXPERT OPINION: Rising multidrug resistance and limited oral options are reshaping cUTI management, necessitating individualized, stewardship-aligned therapy guided by illness severity and local epidemiology. Current regulatory endpoints inadequately reflect patient-centered outcomes, particularly in the context of asymptomatic bacteriuria. Expanding availability of effective oral agents may enable earlier discharge and outpatient care. Integration of rapid diagnostics and risk stratification will be essential to optimize therapy, limit resistance, and improve outcomes.

Humans

Molecular Diagnostics for WHO Priority Bacterial Pathogens: A Bibliometric Mapping of Diagnostic Platforms, Resistance Markers, and Antimicrobial Resistance Research Trends.

Antimicrobial resistance (AMR) constrains effective treatment and carries implications for infection control, surveillance, and public health. The World Health Organization (WHO) priority bacterial pathogen framework has intensified the need for diagnostic innovation by redefining research priorities around organisms combining high disease burden with complex resistance profiles. Molecular diagnostics have accordingly moved beyond culture-based workflows, integrating rapid pathogen identification, resistance-marker detection, genomic surveillance, and clinical decision support. The present study conducted a bibliometric mapping of the literature on WHO priority pathogens. Rather than addressing resistance at a general level or a single pathogen or technology, it integrates priority pathogens, molecular platforms, and resistance markers within a single framework, tracing their joint thematic and temporal evolution along an explicit pathogen-platform-marker axis. Scopus-indexed articles and reviews (2000-2025) were retrieved, yielding 1746 publications after screening adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Analyses used Bibliometrix/Biblioshiny, R, and VOSviewer. The literature expanded markedly after 2018, led by China and the United States. Methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis, Enterococcus faecium, and the Enterobacterales-carbapenemase axis constituted the principal thematic cores, whereas conventional polymerase chain reaction (PCR)/nucleic acid amplification testing (NAAT) and whole-genome sequencing were the dominant platforms. Overall, the field has evolved from pathogen detection into an AMR-centered translational domain encompassing resistance prediction, genomic epidemiology, surveillance, and clinical decision support. Diagnostic development, stewardship, and surveillance depend on hybrid workflows coupling rapid marker-targeted assays with genome-based characterization, delivering actionable resistance within clinically meaningful timeframes, and extending coverage to underrepresented pathogens and platforms.

Humans

"Clinical efficacy and expression of antimicrobial resistance genes after using a novel herbal mouthwash compared to chlorhexidine: A Randomised controlled trial in generalised gingivitis patients".

OBJECTIVES: Chlorhexidine, the gold-standard mouthwash, has several disadvantages, like promotion of antimicrobial resistance. Herbal mouthwashes are emerging as alternatives to chlorhexidine. However, its impact on antimicrobial resistance remains unclear. The aim of the study was to compare the clinical efficacy and the expression of antimicrobial resistance genes of chlorhexidine with a novel herbal mouthwash. DESIGN: Sixty patients with generalised gingivitis were randomly assigned to two groups using block randomisation. After professional mechanical plaque removal patients were instructed to use either chlorhexidine or a novel herbal mouthwash (patented composition) for two weeks. Tetracycline resistance (tetM) and macrolide efflux (mefI) gene expression in subgingival plaque were analysed using real-time polymerase chain reaction. Intragroup comparisons were performed with a paired t-test and Wilcoxon signed-rank test for parametric and nonparametric data. Intergroup comparisons employed unpaired t-test, chi-square test, and Mann-Whitney test. RESULTS: A significant reduction in bleeding, plaque, pocket depth and and patient reported outcomes were noticed in both groups. But reduction in plaque was more significant in chlorhexidine group. tetM and mefI genes significantly upregulated in the chlorhexidine group, while it was downregulated with herbal mouthwash (fold change 1.79&#x202f;&#xb1;&#x202f;0.74 and 0.60&#x202f;&#xb1;&#x202f;0.43 for tetM, and 1.83&#x202f;&#xb1;&#x202f;0.87 and 0.51&#x202f;&#xb1;&#x202f;0.44 for mefI). However, patients' perception of taste, freshness, and overall satisfaction was better in the chlorhexidine group. CONCLUSIONS: The increased expression of antimicrobial resistance genes following chlorhexidine use warrants careful consideration. Herbal mouthwash is an effective, safer alternative with comparable clinical benefits and less impact on antimicrobial resistance.

Humans

Leveraging traveller genomics for LMIC diarrhoeal disease management.

Diarrhoeal pathogens impose a substantial global health burden, disproportionately affecting low- and middle-income countries (LMICs). However, in these settings, health-seeking behaviours, suboptimal microbiological capacity, and challenges in establishing genomics capacity constrain effective surveillance, including surveillance of antimicrobial resistance (AMR). In contrast, high-income countries routinely generate and share large volumes of diarrhoeal pathogen genomes through established systems, with a significant proportion originating from travellers returning from LMICs. These data reveal strong geographical structuring of lineages and clinically relevant AMR patterns, demonstrating untapped potential to support improvements in geographically granulated surveillance to support antimicrobial treatment recommendations. In this opinion article, we outline the potential to integrate traveller-derived microbial genomic data into LMIC public health decision-making and highlight the scientific, ethical, practical, and governance considerations for implementation.

antimicrobial resistance

Quantitative susceptibility mapping in neurodegenerative diseases: An umbrella review of iron-related biomarkers and mechanisms.

Pathological iron accumulation is a common pathophysiological hallmark across multiple neurodegenerative diseases (NDDs), motivating the need for accurate, non-invasive quantification methods. Quantitative susceptibility mapping (QSM) is an advanced magnetic resonance imaging (MRI) technique that enables in vivo measurement of tissue magnetic susceptibility (&#x3c7;), providing a sensitive proxy for iron content. This umbrella review systematically evaluates the diagnostic accuracy, clinical correlations, and distinct iron distribution patterns of QSM in major NDDs, such as Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and atypical Parkinsonism. We included 15 (13/15 were rated Low or Critically Low on AMSTAR 2) systematic reviews and meta-analyses (through July 15, 2026); however, the findings should be interpreted cautiously because of heterogeneity and the low methodological quality. A Corrected Covered Area (CCA) analysis demonstrated only slight overlap of primary studies across the included reviews (CCA&#xa0;=&#xa0;5.42%). Collectively, the evidence indicates that QSM provides comparable or higher diagnostic sensitivity and reliability than conventional R2* and SWI techniques, particularly for deep gray matter structures. The findings support significant iron overload in the substantia nigra, particularly in the pars compacta, as a robust biomarker for PD that correlates with motor severity and disease duration. Furthermore, regional iron profiling in the basal ganglia is critical for differential diagnosis; specifically, elevated &#x3c7; in the putamen and globus pallidus effectively distinguishes multiple system atrophy and progressive supranuclear palsy from idiopathic PD. Distinctively, AD and ALS exhibit specific &#x3c7; alterations in the thalamus, motor cortex, and hippocampus, reflecting divergent iron-related pathophysiological mechanisms, which correlate with cognitive impairment and upper motor neuron signs. Overall, QSM shows diagnostic promise and offers mechanistic insights into iron-related neurodegenerative processes.

Humans

CNNM2 in schizophrenia: multilevel evidence of genetic susceptibility, magnesium homeostasis, neurodevelopment and cognitive dysfunction.

Schizophrenia (SCZ) is a common psychiatric disorder with a complex, genetically and environmentally influenced etiology, but the specific pathogenesis remains unclear. In recent years, the SCZ susceptibility gene CNNM2 (encoding cyclin M2) located at the 10q24.32-33 locus has received widespread attention. The well-validated SCZ risk interval 10q24.32-33 harbors two independent risk variants: rs11191580 in NT5C2 (significantly associated with CNNM2 mRNA and protein levels) and rs7914558 in CNNM2. Results from functional genomic analyses indicate that lower CNNM2 expression is significantly associated with SCZ. Imaging genetics studies have demonstrated that carriers of risk alleles of CNNM2 SNPs exhibit alterations in brain structure. Animal model studies have revealed that Cnnm2 downregulation in mice leads to impairments in sensorimotor gating and cognitive function. As an Mg2+ transporter, CNNM2 primarily maintains systemic Mg2+ homeostasis. According to clinical studies, a proportion of patients with SCZ exhibit reduced Mg2+ concentrations in plasma and cerebrospinal fluid. CNNM2 dysfunction may contribute to the pathology of SCZ by disrupting Mg2+ homeostasis, thereby affecting neurodevelopment and synaptic plasticity. A systematic consolidation of current evidence supporting the involvement of CNNM2 in SCZ pathogenesis provides a direction for further investigation of the pathological mechanisms underlying this disease, and for identification of novel targets for clinical intervention..

Schizophrenia

From commensal to pathobiont: The emergence of virulence-enhanced Escherichia coli in China's food-animal systems - insights with future implications.

A fundamental shift in Escherichia coli epidemiology is being driven by convergence of virulence determinants and antimicrobial resistance within linked human-animal-environment systems. In China, the rapid growth of food-animal production, extensive antimicrobial use, and complex food networks are accelerating the emergence and dissemination of virulence-enhanced E. coli pathobionts. This review synthesizes recent epidemiological, genomics, and outbreak data to characterize China's evolving landscape of food-animal-associated E. coli. We highlight a significant shift from classical pathotypes to hybrid lineages that simultaneously carry virulence factors and last-resort antibiotic resistance determinants, including mcr-1, tet(X4), and blaNDM. These traits disseminate rapidly via plasmid-mediated horizontal gene transfer, facilitating rapid adaptation and enabling cross-sectoral One Health transmission. National surveillance, foodborne outbreak investigations, and whole-genome sequencing data show that food-animal reservoirs are active evolutionary niches that drive pathogen diversity and fitness, rather than serving merely as contamination sources. Whole-genome sequencing also pinpoints high-risk clones (e.g., ST394) and plasmid-mediated co-selection of virulence and AMR. The emergence of hybrid pathotypes (e.g., STEC/ETEC) and AMR-virulence co-selection challenges traditional classification and limits the effectiveness of conventional surveillance approaches. The 2017 colistin ban reduced mcr-1, yet ongoing resistance and emerging tet(X4) demand integrated surveillance. Collectively, these findings call for reconceptualizing E. coli as a dynamic genomic entity embedded within a unified ecological network. Addressing this threat requires an integrated One Health strategy including genomic surveillance, agricultural antimicrobial stewardship, and coordinated food-environment-clinical monitoring to prevent high-risk clone emergence and global spread.

Animals

Emergence of an optrA-positive Enterococcus faecalis ST699 lineage in animal-derived foods in Beijing, China.

Enterococci from animal-derived foods are key reservoirs for antimicrobial resistance (AMR) in the food chain. However, comparative genomic studies investigating the distribution of the oxazolidinone resistance gene optrA among food- and human-derived Enterococci remain limited. This study assessed linezolid-resistant Enterococci from retail meat and healthy humans in Beijing, China (2023-2024). Among 87 isolates, E. faecalis and E. faecium predominated. Food-derived isolates showed broader resistance profiles than human isolates. Fourteen optrA-positive strains were identified, accounting for 92.9% of food isolates. optrA frequently co-localized with erm(A), ant(9)-Ia, and fexA on Tn554-family transposons, suggesting a potentially transferable multidrug resistance module. Notably, an optrA-positive E. faecalis ST699 clone was identified for the first time in Chinese retail meat. This clone formed a distinct lineage and carried a complete Tn554-optrA island. A representative ST699 isolate exhibited enhanced fitness and virulence potential in the Galleria mellonella model. These findings highlight animal-derived foods as important reservoirs of linezolid-resistant Enterococci and provide genomic evidence consistent with their role as potential sources of optrA-mediated resistance. The emergence of a multidrug-resistant E. faecalis ST699 clone with enhanced fitness characteristics underscores the need for continued surveillance of foodborne antimicrobial resistance within the One Health framework.

Enterococcus faecalis

The Brazilian contribution to ant toxinology: challenges and perspectives.

Ant toxinology in Brazil is a small but growing field that has revealed wide biochemical diversity and clear potential for bioprospecting therapeutic molecules. This review compiles the Brazilian contribution, focusing on advances in the characterization of venoms from medically and ecologically important species of Dinoponera, Solenopsis, Paraponera, Pachycondyla, Neoponera, and Ectatomma. Brazilian groups applied omics approaches, including transcriptomics and proteomics, to resolve the composition of these venoms and identified peptide-rich arsenals with antimicrobial, antiparasitic, antitumor, and neuroactive activity. Studies of venom phenotypic plasticity showed ecological factors such as diet and seasonality shape venom composition. Two challenges persist: assigning function to still unidentified components and obtaining venom in the quantities that broad analysis requires. The near-term prospects are the rational design of peptide analogues with improved activity and continued bioprospecting of new species, which together position Brazil as a central contributor to ant toxinology.

Animals

Antibiotic Self-Medication and Public Awareness During the 2023 Gaza War: A Cross-Sectional Investigation.

BACKGROUND: Antimicrobial resistance is driven by inappropriate antibiotic use, particularly self-medication. The 2023 Gaza War disrupted healthcare services, increasing resistant infections and reliance on self-treatment practices. OBJECTIVES: To determine the prevalence of antibiotic self-medication and assess public awareness during the 2023 Gaza War. METHODS: A cross-sectional survey was conducted between May and October 2025 among adults residing in the Gaza Strip during the 2023 Gaza War. A multistage non-probability recruitment strategy, organized across predefined governorate and residential-setting strata, was used to recruit 422 participants from primary healthcare centers, community pharmacies, and displacement shelters. The questionnaire demonstrated good internal consistency (Cronbach's &#x3b1;&#x202f;=&#x202f;0.857). Ethical approval was obtained from the relevant institutional review board, and informed consent was secured from all participants. RESULTS: The overall KAP score was moderate (67.46%), with attitudes scoring highest (74.62%), followed by knowledge (66.23%) and practices (61.52%). Reported antibiotic self-medication increased from 60.4% before the war to 80.6% during the war (p < 0.001), with significant changes in reasons for self-medication and antibiotic procurement sources. The mean antimicrobial-resistance perception score was 82.19 &#xb1; 11.10%, and knowledge was strongly correlated with the total KAP score (r&#x202f;=&#x202f;0.836, p < 0.001). CONCLUSIONS: Reported antibiotic self-medication was markedly higher during the 2023 Gaza War despite moderate public awareness, highlighting the urgent need for education, antibiotic stewardship, and improved healthcare accessibility.

Gaza War 2023

MIC-based tuberculosis drug susceptibility testing using Sensititre MYCOTB: a diagnostic accuracy meta-analysis.

Accurate drug susceptibility testing (DST) is crucial for designing effective regimens for multidrug-resistant (MDR) and pre-extensively drug-resistant tuberculosis (pre-XDR TB). Sensititre MYCOTB enables simultaneous determination of minimum inhibitory concentrations (MICs) for multiple drugs, but its diagnostic performance varies across studies. This meta-analysis evaluated the diagnostic performance of Sensititre MYCOTB for key MDR and pre-XDR TB drugs. The protocol was registered in PROSPERO (CRD420251230599). PubMed, Cochrane, Google Scholar, Scopus, ONOS, Web of Science, ScienceDirect, and registries were systematically searched for studies published between 2010 and 2025. Studies comparing the Sensititre MYCOTB with reference DST for Mycobacterium tuberculosis complex (MTBC) were included. Bias assessment and pooled diagnostic accuracy estimates were generated. Fourteen studies, including 1,728 isolates, were analyzed. Rifampicin and isoniazid demonstrated high sensitivity (0.976 [95% CI: 0.94-0.99] and 0.977 [95% CI: 0.95-0.99]) and specificity (0.958 [95% CI: 0.84-0.98] and 0.957 [95% CI: 0.83-0.99], respectively) with low heterogeneity. Amikacin, kanamycin, and ofloxacin demonstrate good diagnostic accuracy, with high specificity (>0.98 [95% CI]). Moderate diagnostic accuracy was observed for ethambutol, streptomycin, ethionamide, and rifabutin. Cycloserine, moxifloxacin, and para-aminosalicylic acid showed inconsistent performance despite excellent specificity (>0.97 [95% CI]). Sensitivity analysis partially improved pooled sensitivity for moxifloxacin 0.801 (95% CI: 0.585-0.924) and para-aminosalicylic acid 0.76 (95% CI: 0.518-0.894), whereas cycloserine remained at 0.436 (95% CI: 0.190-0.725), although heterogeneity persisted. Sensititre MYCOTB DST demonstrates high diagnostic accuracy for MDR-TB and pre-XDR-TB drugs, while caution is required with cycloserine, moxifloxacin, and para-aminosalicylic acid. These findings support the integration of MIC-based testing into clinical decision-making.

Microbial Sensitivity Tests

Regional genomic analysis of lineage distribution and transferable multidrug resistance among chicken-associated Salmonella Kentucky isolates in China.

Salmonella enterica serovar Kentucky is an important multidrug-resistant foodborne pathogen in the poultry meat supply chain. Although recent broader genomic studies have elucidated the population structure and epidemiological significance of major lineages in China (e.g., ST198 and ST314), the regional dynamics within local poultry supply chains remain insufficiently characterized. In this study, 31 chicken meat-derived isolates from Shanghai and 39 publicly available genomes from China were analyzed using antimicrobial susceptibility testing, whole-genome sequencing, phylogenetic analysis, conjugation experiments, and complete sequencing of representative plasmids. This enabled a systematic characterization of the molecular epidemiological features of the population and the mechanisms underlying resistance dissemination. Population genomic analysis revealed a lineage composition markedly different from the global epidemiological pattern: ST314 was the predominant sequence type among the Shanghai chicken-derived isolates (74.2%), whereas the internationally recognized high-risk clone ST198 accounted for only 25.8% of the local isolates. However, risk stratification analysis indicated that although ST198 was detected less frequently, it carried a significantly greater burden of acquired resistance genes and therefore represented a higher-risk resistant lineage. Functional and structural validation further elucidated the molecular basis of resistance dissemination within this high-risk lineage. Conjugation experiments confirmed the co-transfer of a multidrug resistance module carrying blaTEM-1 and blaCTX-M-267 to the recipient strain Escherichia coli J53. Complete plasmid analysis revealed that these two &#x3b2;-lactam resistance genes were co-localized on a 242-kb transferable plasmid flanked by Tn1331, Tn3, and multiple transposase-associated elements, thereby providing a structural basis for their horizontal transfer. This study provides important molecular epidemiological evidence for lineage-specific surveillance and risk-stratified control of resistant Salmonella in the poultry meat supply chain and further underscores the need for continuous monitoring of mobile genetic elements within a One Health framework.

Animals