Population-based incidence and characteristics of community-onset Staphylococcus aureus infections with bacteremia in 4 metropolitan Connecticut areas, 1998.

This study retrospectively analyzed the magnitude and epidemiology of community-onset Staphylococcus aureus (COSA) infections and methicillin-resistant S. aureus (MRSA) infections in 4 Connecticut metropolitan areas (population, 1.1 million). The study looked at hospital medical records of persons admitted with S. aureus bacteremia in 1998. COSA was categorized as "health care associated," "with underlying medical condition," or "no underlying medical condition." Overall, 48% of S. aureus bacteremic infections were COSA (incidence, 17 cases/100,000 persons). Incidence increased with age and higher population density. In all, 62% of infections were health care associated; 85% of the remaining cases had underlying medical conditions. MRSA accounted for 16% of health care-associated cases and cases with underlying conditions but no cases with no underlying conditions. COSA bacteremic infections are as common as those due to pneumococci. MRSA is a well-established cause of COSA among persons at high medical risk for S. aureus infection. Additional study to understand community-onset MRSA acquisition is needed.