ST8-t008-SCC mec IV methicillin-resistant Staphylococcus aureus in retail fresh cheese.

This study reports the finding of 3 ST8-t008-SCC mec IVa (2B) methicillin-resistant Staphylococcus aureus (MRSA) strains in fresh cheese purchased within a single market in Costa Rica. In line with the finding of the resistance genes mecA, blaZ, mph(C), and msr(A) in their genomes, these bacteria showed phenotypic resistance to multiple β-lactams and erythromycin. In addition, they carry genes for acquired resistance to aminoglycosides (aph(3')-III) and fosfomycin (fosD), and genes for a myriad of virulence factors, including adhesins, hemolysins, and exotoxins. Our strains share multiple genomic features with MRSA from the USA300 lineage, which is a widely distributed and highly virulent strain implicated in community infections. As a result, consuming these or similar products could lead to multidrug infections in susceptible individuals. These results highlight safety deficiencies in cheese production practices and emphasize the risk of foodborne transmission of hard-to-treat ST8 MRSA strains.