Abstract

Background:
Coagulase-negative staphylococci, such as Staphylococcus cohnii are increasingly recognized as crucial reservoirs of antimicrobial resistance (AMR) genes. However, their role in the dissemination of multidrug resistance within livestock populations, which represents a potential threat to public health through the food chain, remains insufficiently investigated.

Aim:
The aim of this study was to characterize the AMR profiles of S. cohnii isolates from Chinese swine farms using integrated phenotypic and genotypic approaches.

Methods:
This study characterized 32 porcine-derived S. cohnii isolates from Jilin Province, China. Antimicrobial susceptibility testing against 20 antibiotics was performed using the agar dilution method, and the genomic basis of resistance was investigated through second-generation sequencing followed by comprehensive antibiotic resistance gene analysis.

Results:
Phenotypic testing revealed universal resistance (100%) to 11 antibiotics, including ampicillin and tetracycline. Genomic analysis identified 32 distinct resistance genes, with six of them (e.g., fusF, salE, vanTG) present in all isolates. Critically, multiple transferable multidrug-resistant genes were detected, including ermB (53.13%), ermC (18.75%), and cfrA (12.5%). Furthermore, silent glycopeptide resistance genes (e.g., vanTG, vanYB) were identified despite phenotypic susceptibility to vancomycin.

Conclusion:
This study establishes porcine S. cohnii as a significant reservoir of diverse and mobile resistance genes, including silent determinants with potential for horizontal transfer. These findings underscore the necessity of integrating genomic surveillance of commensal staphylococci in livestock within a One Health framework to mitigate the dissemination of resistance to human pathogens.

Key words: Staphylococcus cohnii; Antimicrobial resistance; Swine; Resistance genes; Second-generation sequencing analysis.