684. Skin and Soft-Tissue Infections in a Northern California Population: Incidence, Health Services Use and Microbiology in the Era of Methicillin-Resistant Staphylococcus Aureus
Session: Poster Abstract Session: Skin, Soft Tissue and Joint Infections
Friday, October 21, 2011
Room: Poster Hall B1
  • IDSA 2011 poster 2011-09-13.pdf (174.6 kB)
  • Background:  Skin and soft tissue infections (SSTIs) are a major cause of hospitalizations and outpatient visits in the United States, and their numbers have increased in recent years contemporaneous with the emergence and rapid spread of drug-resistant strains of  S. aureus (SA) such as methicillin-resistant SA (MRSA).

    Methods:  Using electronic databases of Kaiser Permanente Northern California (KPNC), we identified all clinically-diagnosed SSTIs among KPNC members from 2007 to 2009.  The majority of cases were coded as cellulitis and abscess. Chronic decubitis ulcer, gangrene, necrotizing fasciitis, device-related and nosocomial infections were excluded. Population-based incidence rates were calculated using the KPNC membership as the denominator. We identified the frequency of bacteriological testing, the role of SA and MRSA, and use of health care services associated with SSTIs. Multivariate negative binomial regression models were used to identify racial differences in SSTI incidence and likelihood of MRSA. Reported results were significant at p<=0.01.

    Results:  We identified 468,000 SSTIs, corresponding to an overall incidence rate of 497 episodes per 10,000 person-years. Among SSTI episodes, 23% had a culture, 57% of cultures were positive for a potentially clinically-relevant organism and, among those, 82% were SA.  Half of SA episodes were MRSA.  Compared to whites, Asians and Hispanics had lower risk of SSTI (risk ratios (RR): 0.54 and 0.79 respectively).  Among episodes with a culture-confirmed pathogen, African-Americans and Hispanics had a higher risk of it being MRSA compared to that of whites (RR: 1.31  and 1.12  respectively), while Asians had a decreased risk (RR: 0.76).  On average, an SSTI episode included 1.25 clinic visits, 0.11 Emergency Department visits, and 0.17 hospital days. Only 3% of episodes included a hospital stay. Most episodes (79%) consisted of a single outpatient visit.

    Conclusion: In this population, each year there were approximately 5 SSTIs for every 100 years of person-time. One out of four episodes were cultured. SA was the most common pathogen isolated, half of it being MRSA. Hispanics and African-Americans had higher risk of MRSA than Whites. An SSTI was associated with non-trivial health care use.

    Subject Category: N. Hospital-acquired and surgical infections, infection control, and health outcomes including general public health and health services research

    G.Thomas Ray, MBA, Division of Research, Kaiser Permanente, Oakland, CA, Jose A. Suaya, MD, PhD, US Global Health Outcomes, GlaxoSmithKline, Philadelphia, PA and Roger Baxter, MD, Kaiser Permanente Vaccine Study Center, Oakland, CA


    G. T. Ray, GlaxoSmithKline: Research Contractor, Research support
    Pfizer: Research Contractor, Research support

    J. A. Suaya, GlaxoSmithKline: Employee, Salary

    R. Baxter, GlaxoSmithKline: Investigator, Research grant
    Pfizer: Investigator, Research grant
    Sanofi Pasteur: Investigator, Research grant
    Merck: Investigator, Research grant
    Novartis: Investigator, Research grant
    AstraZeneca: Investigator, Research grant

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.