Characterization of Staphylococcus aureus isolated from tilapia and utensils used in the commerciali- zation of tilapia in the street markets of a semi-arid Brazilian municipality.

BACKGROUND: The production and commercialization of tilapia (Oreochromis niloticus) is fundamentally important to the semi-arid region of northeastern Brazil. In this region, one of the main forms of commercialization occurs in street markets (fairs). A high incidence of methicillin-resistant Staphylococcus aureus (MRSA) strains was previously detected in different food-related environments in Brazil. However, limited data is available about the presence of MRSA in street markets commercializing tilapias. In this study, we identified Staphylococcus aureus from tilapia and utensils used in the commercialization of tilapia in the street markets of a semi-arid Brazilian municipality and characterized the virulence potential of the isolates by analyzing their β-lactam resistance, intercellular adhesion and enterotoxin genes.

METHODS: The study used samples from the 5 main markets in the city. Phenotypic tests to determine antimicrobial resistance, exopolysaccharide (EPS) production, the potential for biofilm formation and cell surface hydrophobicity were conducted on S. aureus isolates. The presence of antimicrobial resistance genes (mecA and blaZ), potential biofilm production genes (icaA and icaD) and enterotoxin (se) genes was investigated.

RESULTS: Coagulase-positive staphylococci (CoPS) were detected in samples from all markets in discordance with the legal limits in force. Twelve isolates were confirmed to be S. aureus. Ten isolates demonstrated multidrug resistance (MDR). All isolates were able to produce EPS and form biofilms. Eight isolates exhibited strong hydrophobicity and six a high potential for biofilm formation. Twelve isolates were positive for mecA, blaZ, icaD and sed.

CONCLUSIONS: Tilapia marketed in unsuitable conditions may be a vehicle for staphylococcal food poisoning and for the dissemination of MRSA to consumers. Additionally, the ability of the isolates to produce biofilms is an alert to the presence and persistence of these virulent microorganisms on utensils used for the commercial distribution of tilapia.