Epidemiology and clonality of community-acquired methicillin-resistant Staphylococcus aureus in Minnesota, 1996-1998

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged among patien ts in the general population who do not have established risk factors for M RSA. Records from 10 Minnesota health facilities were reviewed to identify cases of MRSA infection that occurred during 1996-1998 and to identify whic h cases were community acquired. Susceptibility testing and pulsed-field ge l electrophoresis (PFGE) subtyping were performed on available isolates. A total of 354 patients (median age, 16 years) with community-acquired MRSA ( CAMRSA) infection were identified. Most case patients (299 [84%]) had skin infections, and 103 (29%) were hospitalized. More than 90% of isolates were susceptible to all antimicrobial agents tested, with the exception of beta -lactams and erythromycin. Of 334 patients treated with antimicrobial agen ts, 282 (84%) initially were treated with agents to which their isolates we re nonsusceptible. Of 174 Minnesota isolates tested, 150 (86%) belonged to 1 PFGE clonal group. CAMRSA infections were identified throughout Minnesota ; although most isolates were genetically related and susceptible to multip le antimicrobials, they were generally nonsusceptible to initial empirical therapy.