Emergence of two populations of methicillin-resistant Staphylococcus aureus with distinct epidemiological, clinical and biological features, isolated from patients with community-acquired skin infections.

BACKGROUND: Community-acquired skin and soft-tissue infections due to methicillin-resistant Staphylococcus aureus (MRSA) are an emerging clinical and epidemiological problem. OBJECTIVES: To characterize community-acquired skin infections caused by S. aureus, and especially MRSA. METHODS: From November 1999 to December 2003, we conducted in a French hospital a prospective epidemiological, clinical and bacteriological study of skin infections acquired in the community, applying strict criteria for true community-acquired MRSA (CA-MRSA) and health-care-associated MRSA (HCA-MRSA). RESULTS: One hundred and ninety-seven patients had 207 skin infections (154 primary and 53 secondary infections). Twenty-two (11%) patients had skin infections caused by MRSA. The incidence of MRSA skin infections acquired in the community rose from 4% in 2000 to 17% in 2003, but the increase was not statistically significant. Six patients (3%) were infected by CA-MRSA and 15 (8%) by HCA-MRSA; one patient was lost to follow-up and could not be classified. CA-MRSA and HCA-MRSA had different epidemiological, clinical and biological characteristics. CA-MRSA infections were more severe than HCA-MRSA infections: all the CA-MRSA infections (six of six, 100%) required surgical treatment, compared with only two (15%) of 13 with HCA-MRSA infection (P < 0.001). CA-MRSA all belonged to the same clonal strain, harbouring an agr type 3 allele and the Panton-Valentine leucocidin genes (not detected in HCA-MRSA) and possessing a specific antibiotype. CONCLUSIONS: Two populations of MRSA causing skin infections are emerging in the French community, with distinct epidemiological, clinical and biological characteristics.