ABSTRACT
PURPOSE: The study's purpose was to elucidate the evolutionary, microbiologic, and clinical characteristics of methicillin-resistant Staphylococcus aureus (MRSA) infections. METHODS: MRSA 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. RESULTS: Over the 15-year period, 1888 cases of MRSA were identified; 65% were community acquired. The incidence (155 infections/100000 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. CONCLUSIONS: Community-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.
Subject(s)
Cross Infection/epidemiology , Cross Infection/microbiology , Methicillin Resistance , Staphylococcal Infections/epidemiology , Staphylococcus aureus/drug effects , Adult , Anti-Bacterial Agents/therapeutic use , California/epidemiology , Clindamycin/therapeutic use , Community-Acquired Infections/epidemiology , Community-Acquired Infections/microbiology , Cross Infection/drug therapy , Drug Resistance, Bacterial , Female , Humans , Incidence , Male , Staphylococcal Infections/diagnosis , Staphylococcal Infections/drug therapy , Staphylococcus aureus/geneticsABSTRACT
We describe a case series of group A Streptococcus (GAS) necrotizing fasciitis occurring over a 10-week period in military recruits undergoing intense physical training. These cases highlight that GAS may cause life-threatening infections in addition to mild diseases such as pharyngitis. This series suggests that the incidence of severe GAS infections may be increasing in certain populations and it emphasizes the importance of considering prophylactic measures against GAS in high-risk populations.