Staphylococcus aureus-associated skin and soft tissue infections in ambulatory care

Purpose: To examine trends in ambulatory care visit rates for skin and soft tissue infections (SSTIs) typical of Staphylococcus aureus.

Methods: Data were analyzed from the 1999-2006 National Ambulatory Medical Care Survey (NAMCS) and National Hospital Ambulatory Medical Care Survey (NHAMCS), annual national probability sample surveys of visits to U.S. physician offices and hospital emergency departments (EDs) and outpatient departments (OPDs). SSTIs typical of S. aureus (e.g., cellultis, abscess) were defined by ICD-9-CM diagnosis codes. Data were weighted to produce national estimates. Two years of data were combined to produce more reliable estimates. Trends were tested using a weighted least-squares regression analysis.

Results: In 2005/06, 15.2 million annual visits were made to U.S. ambulatory care providers for SSTIs typical of S. aureus; 73% of these visits were initial visits. The proportion of ED visits with a diagnosis of SSTI typical of S. aureus was 3.3% in 2005/06 and 1.7% in 1999/2000 (p< 0.05). The ambulatory care visit rate for SSTIs typical of S. aureus rose from 348 per 10,000 population in 1999/2000 to 520 per 10,000 in 2005/06 (p< 0.05). Visit rates for these conditions doubled in EDs and increased by 50% in physician offices during the study period (p< 0.05); no change was observed in OPDs.

Conclusions: Visit rates for SSTIs typical of S. aureus increased dramatically in EDs and moderately in physician offices. This may reflect an increase in SSTI burden due to recent emergence of epidemic community strains of methicillin-resistant S. aureus or changes in care-seeking behavior.