Interplay between enterotoxigenicity, antimicrobial resistance, and persistence mechanisms in Staphylococcus spp....

Staphylococcus spp. represent a persistent concern in food-related environments due to the interplay between virulence traits, antimicrobial resistance, and persistence mechanisms. This study comparatively characterized antimicrobial resistance, persistence phenotypes, and enterotoxigenic potential in 83 Staphylococcus isolates from food, humans, and animals. Phenotypic production of staphylococcal enterotoxins (SEA-SEE) was detected in 59% of isolates, including coagulase-negative staphylococci (CoNS), accounting for 20% of enterotoxigenic isolates. Classical se genes (sea-see) were identified in 46% of isolates, with sea and sec most prevalent. None of the isolates was fully susceptible to all tested antibiotics and 48% were multidrug-resistant, with the highest resistance rates for erythromycin, penicillin, and clindamycin. The mecA gene was detected in 61% of isolates; however, phenotypic cefoxitin resistance was mainly observed in human-derived isolates, indicating mecA presence did not consistently correspond to phenotypic expression. Higher EtBr IC₅₀ values were associated with increased tolerance to ciprofloxacin and erythromycin, indicating a link between efflux activity and antimicrobial tolerance. All isolates formed biofilm, with significantly higher biofilm intensity in enterotoxin-positive food-derived isolates (p = 0.002), demonstrating an association between enterotoxigenicity and persistence traits. Comparative analysis revealed higher antimicrobial resistance in human- and animal-derived isolates, whereas food-derived isolates showed a combination of enterotoxigenicity and strong biofilm formation. These findings indicate that food-associated staphylococci may pose a relevant food safety risk due to the interplay between toxin production and persistence. Furthermore, the detection of enterotoxigenic CoNS supports their consideration alongside S. aureus in food safety assessments.