Human MRSA Isolates with Novel Genetic Homolog, Germany

To the Editor: Methicillin-resistant Staphylococcus aureus (MRSA) represents a major cause of hospital-, community- and livestock-acquired infections that are increasingly difficult to manage (1–3). Detection and identification of MRSA by culture and nucleic acid–based methods is challenged by heterogeneous penicillin-binding protein 2a (PBP2a) expression and variability of the staphylococcal cassette chromosome (SCCmec) elements. Recently, a new SCCmec element (XI) carried in bovine and human isolates was described (4,5). This SCCmec element contains a novel mecA homolog, designated mecALGA251, that is not detectable by usual mecA-specific PCR approaches and PBP2a agglutination tests. Garcia-Alvarez et al. reported this novel mecA homolog exhibited 70% identity at DNA level to the mecA gene, and suggested these strains were transmitted from livestock to humans (4).