Occurrence of Presumptive Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci in Retail Fish and Seafood Products: A Culture-Based Screening Study

Background: Fish and seafood products may act as vehicles for the dissemination of antimicrobial-resistant bacteria through the food chain. Particular concern is associated with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). This study evaluated the occurrence of S. aureus, Enterococcus spp., and presumptive MRSA and VRE in retail fish and seafood products using culture-based screening methods. Methods: A total of 99 fish and seafood samples purchased from retail outlets in northern Poland were analyzed using selective microbiological culture methods. Presumptive MRSA and VRE were screened on chromogenic selective media. Differences between product categories were assessed using non-parametric statistical tests and chi-square analysis. Results: S. aureus was detected in 80.8% of samples, with significantly higher contamination levels in seafood than in fish (p = 0.002). Presumptive MRSA isolates were detected in 27.3% of samples. Enterococcus spp. were found in 49.5% of samples, with significantly higher prevalence and counts in unpackaged products (p < 0.05). Presumptive VRE isolates occurred in 17.2% of samples, while simultaneous occurrence of presumptive MRSA and VRE was observed in 9.1% of samples. Conclusions: Retail fish and seafood products may constitute a reservoir of presumptive antimicrobial-resistant bacteria. The higher contamination of unpackaged products highlights the importance of hygienic handling practices. Molecular confirmation and antimicrobial susceptibility testing are needed to further assess the public health significance of these microorganisms.