MRSA Skin Infection in Athletes

Nosocomial infections of methicillin-resistant Staphylococcus aureus (MRSA) (ie, hospital-acquired MRSA [HA-MRSA]) have been reported since 1963.1 Community-acquired MRSA (CA-MRSA) infections are a more recent variant and are becoming more common in athletes2,3,4,5,6,7,8 and active individuals since the first reported cases in a high school wrestling team in 19939 and a British rugby club in 1998.10 CA-MRSA differs from HA-MRSA in its genetic makeup, increased pathogenicity, and susceptibility to antibiotic treatment.

The resistance of MRSA to beta-lactam antibiotics is due to the presence of the mecA gene sequence. The mecA gene produces transpeptidase PBP2a (penicillin-binding peptide) that decreases the bacterial affinity of the beta-lactam antibiotics. The mecA gene is a subset of a larger SCCmec gene that is responsible for the differences seen in HA-MRSA and CA-MRSA bacteria.11

Several variations of the SCCmec gene have been sequenced; SCCmec gene types I, II, and III are found in HA-MRSA, whereas CA-MRSA bacteria have the SCCmec type IV gene.12 The SCCmec gene types I-III are larger genes, and other portions of the gene provide resistance factors against other antibiotic classes. The type IV SCCmec gene is a small gene that has fewer of these additional resistance factors. This difference may explain the continued susceptibility of CA-MRSA compared with HA-MRSA to some oral antibiotics such as trimethoprim-sulfamethoxazole.