Epidemiology of methicillin-resistant Staphylococcus aureus at a pediatric healthcare system, 1991-2003

The emergence and epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) at a Minneapolis pediatric healthcare facility was investigated.

Children with MRSA infections from January 1991 to December 2003 were classified as community-associated (CA) or healthcare-associated (HA) using established criteria. Isolates were subtyped using pulsed-field gel electrophoresis and grouped into pulsed-field types (PFTs). Case and isolate characteristics were compared and temporal trends were assessed.

The first isolate classified as CA-MRSA in this healthcare facility was identified in 1991. CA-MRSA cases (n = 188) were more likely than HA-MRSA cases (n = 83) to have a skin or soft tissue infection (80% versus 59%) and to belong to a racial or ethnic minority group (82% versus 55%), whereas HA-MRSA cases were younger (median age, 3.4 years versus 4.9 years). The proportion of both CA- and HA-MRSA isolates susceptible to clindamycin and erythromycin declined during the study period. Isolates classified as CA-MRSA were more likely than HA-MRSA isolates to be USA300 (21% versus 11%, P = 0.05) and USA400 (62% versus 31%, P < 0.001) PFTs. Associations between case race/ethnicity and isolate PFT were observed independent of case classification.

CA-MRSA is well established in this pediatric population. Although no discernable changes in CA- or HA-MRSA case characteristics were documented during the study period, significant changes were observed in CA-MRSA isolate characteristics, indicating that this pathogen continues to evolve.