Email updates

Keep up to date with the latest news and content from BMC Infectious Diseases and BioMed Central.

Open Access Highly Accessed Open Badges Research article

Incidence, microbiology, and patient characteristics of skin and soft-tissue infections in a U.S. population: a retrospective population-based study

Gary Thomas Ray1*, Jose Antonio Suaya2 and Roger Baxter3

Author Affiliations

1 Division of Research, Kaiser Permanente Medical Care Program, Northern California Region, 2000 Broadway, Oakland, CA 94612, USA

2 Health Outcomes, North America Vaccine Development, GlaxoSmithKline Vaccines, 16th Street, 200 N, Philadelphia, PA, 19102, USA

3 Kaiser Permanente Vaccine Study Center and The Permanente Medical Group, 1 Kaiser Plaza, Oakland, CA, 94612, USA

For all author emails, please log on.

BMC Infectious Diseases 2013, 13:252  doi:10.1186/1471-2334-13-252

Published: 30 May 2013



Skin and soft tissue infections (SSTIs) are commonly occurring infections with wide-ranging clinical manifestations, from mild to life-threatening. There are few population-based studies of SSTIs in the period after the rapid increase in community-acquired methicillin-resistant Staphyloccus aureus (MRSA).


We used electronic databases to describe the incidence, microbiology, and patient characteristics of clinically-diagnosed skin and soft tissue infections (SSTIs) among members of a Northern California integrated health plan. We identified demographic risk factors associated with SSTIs and MRSA infection.


During the three-year study period from 2009 to 2011, 376,262 individuals experienced 471,550 SSTI episodes, of which 23% were cultured. Among cultured episodes, 54% were pathogen-positive. Staphylococcus aureus (S. aureus) was isolated in 81% of pathogen-positive specimens, of which nearly half (46%) were MRSA. The rate of clinically-diagnosed SSTIs in this population was 496 per 10,000 person-years. After adjusting for age group, gender, race/ethnicity and diabetes, Asians and Hispanics were at reduced risk of SSTIs compared to whites, while diabetics were at substantially higher risk compared to non-diabetics. There were strong age group by race/ethnicity interactions, with African Americans aged 18 to <50 years being disproportionately at risk for SSTIs compared to persons in that age group belonging to other race/ethnicity groups. Compared to Whites, S. aureus isolates of African-Americans and Hispanics were more likely to be MRSA (Odds Ratio (OR): 1.79, Confidence Interval (CI): 1.67 to 1.92, and, OR: 1.24, CI: 1.18 to 1.31, respectively), while isolates from Asians were less likely to be MRSA (OR: 0.73, CI: 0.68 to 0.78).


SSTIs represent a significant burden to the health care system. The majority of culture-positive SSTIs were caused by S. aureus, and almost half of the S. aureus SSTIs were methicillin-resistant. The reasons for African-Americans having a higher likelihood, and Asians a lower likelihood, for their S. aureus isolates to be methicillin-resistant, should be further investigated.

Skin and soft-tissue infections; Methicillin-resistant staphylococcus aureus; Incidence; Epidemiology