Article ID Journal Published Year Pages File Type
2721193 The American Journal of Medicine 2006 9 Pages PDF
Abstract

PurposeThe study’s purpose was to elucidate the evolutionary, microbiologic, and clinical characteristics of methicillin-resistant Staphylococcus aureus (MRSA) infections.MethodsMRSA cases from military medical facilities in San Diego, from 1990 to 2004, were evaluated and categorized as community-acquired or nosocomial. Sequence type, staphylococcal chromosomal cassette gene type, and Panton-Valentine leukocidin gene status were determined for a subset of isolates.ResultsOver the 15-year period, 1888 cases of MRSA were identified; 65% were community acquired. The incidence (155 infections/100 000 person-year in 2004) and household-associated cases rapidly increased since 2002. Among persons with community-acquired MRSA, 16% were hospitalized and only 17% were initially given an effective antibiotic. Community-acquired MRSA cases compared with nosocomial MRSA cases were more often soft-tissue and less often urinary, lung, or bloodstream infections (P < .001). Patients with community-acquired MRSA were younger (22 vs 64 years, P < .001) and less likely to have concurrent medical conditions (9% vs 98%, P < .001). Clindamycin resistance increased among community-acquired MRSA isolates during 2003 and 2004 compared with previous years (79% vs 13%, P < .001). Genetically, nosocomial MRSA isolates were significantly different than those acquired in the community. Although community-acquired MRSA isolates were initially diverse by 2004, one strain (staphylococcal chromosomal cassette type IV, sequence type 8, Panton-Valentine leukocidin gene positive) became the predominant isolate.ConclusionsCommunity-acquired and intrafamilial MRSA infections have increased rapidly since 2002. Our 15 years of surveillance revealed the emergence of distinct community-acquired MRSA strains that were genetically unrelated to nosocomial MRSA isolates from the same community.

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