Staphylococcus epidermidis causes significant healthcare-associated infections. The most significant obstacles to treatment are due to antibiotic resistance and biofilm formation. This bacterium belongs to a group called coagulase-negative staphylococcus (CoNS) and its increasing association with nosocomial infections highlights its pathogenic potential. S. epidermidis is considered to be a reservoir of antibiotic resistance genes.
Ready-to-eat foods (RTE) foods are occasionally manufactured under suboptimal hygienic conditions, exposing them to potential microbial contamination since they may harbor a wide range of opportunistic microorganisms. In this research study at University of Warnia and Mazury (Poland), food samples including cheese, cured meats, hamburgers, and juices were sampled and 26 Staphylococcus epidermidis isolates were subjected to whole-genome sequencing (WGS) followed by bioinformatics analyses.
Antimicrobial susceptibility testing (AST) was conducted against this pathogen using a broad range of antimicrobial agents including aminoglycosides, beta-lactams, fluoroquinolones, glycopeptides, lincosamides, macrolides, nitrofurantoins, oxalidinones, phenicols, steroids, sulphonamides, and tetracyclines. In fact, authors used several antibiotics (from TOKU-E) in their study including Gentamicin, Azithromycin, Erythromycin, Oxacillin, Linezolid, Nitrofurantoin, Tetracycline, Trimethoprim, Trimethoprim/Sulfamethoxazole, Clindamycin, Fusidic Acid, Chloramphenicol, and Moxifloxacin.
Minimum inhibitory concentrations (MICs) were determined as the lowest antibiotic concentration at which no visible bacterial growth was observed using the broth microdilution method as outlined by EUCAST (European Committee on Antimicrobial Susceptibility Testing).
Sequence typing evealed a remarkable 17 distinct sequence types, reflecting a high level of genetic diversity. Phenotypic resistance to Erythromycin was most prevalent, followed by resistance to Clindamycin.
Genomic analysis found multiple antimicrobial resistance genes such as norA/C, vanT, mecA, dfrC. The potential for horizontal gene transfer to commensal or pathogenic bacteria highlights the need for increased surveillance. S. epidermidis is not used for any technological purpose in the food industry. Thus, its presence in these prepared food products may reflect insufficient hygiene practices during the food processing step. This study highlights the importance of including CoNS in food safety monitoring programs.
Reference
Byczkowska-Rostkowska Z, Gajewska J and Chajęcka-Wierzchowska W (2025) Whole genome analysis and antimicrobial resistance assessment of Staphylococcus epidermidis isolated from food sources. Sci. Total Environ. 993:179999 Link.