MRSA and Skin Infections, Alaska | CDC EID

EID Journal Home > Volume 16, Number 5–May 2010

Volume 16, Number 5–May 2010
Research
Methicillin-Resistant Staphylococcus aureus Carriage and Risk Factors for Skin Infections, Southwestern Alaska, USA
A. Michal Stevens, Thomas Hennessy, Henry C. Baggett, Dana Bruden, Debbie Parks, and Joseph Klejka
Author affiliations: Centers for Disease Control and Prevention, Anchorage, Alaska, USA (A.M. Stevens, T. Hennessy, D. Bruden, D. Parks); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (H.C. Baggett); and Yukon Kuskokwim Heath Corporation, Bethel, Alaska, USA (J. Klejka)

Suggested citation for this article

Abstract
Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are common in southwestern Alaska. Outbreak strains have been shown to carry the genes for Panton-Valentine leukocidin (PVL). To determine if carriage of PVL-positive CA-MRSA increased the risk for subsequent soft tissue infection, we conducted a retrospective cohort study by reviewing the medical records of 316 persons for 3.6 years after their participation in a MRSA nasal colonization survey. Demographic, nasal carriage, and antimicrobial drug use data were analyzed for association with skin infection risk. Skin infections were more likely to develop in MRSA carriers than in methicillin-susceptible S. aureus carriers or noncarriers of S. aureus during the first follow-up year, but not in subsequent years. Repeated skin infections were more common among MRSA carriers. In an area where PVL-containing MRSA is prevalent, skin infection risk was increased among MRSA nasal carriers compared with methicillin-susceptible S. aureus carriers and noncarriers, but risk differential diminished over time.
Methicillin-resistant Staphylococcus aureus (MRSA) has become a primary cause of skin and soft tissue infections among persons without extensive exposure to healthcare settings. Nasal carriage of S. aureus is a known risk factor for these infections (1–3) and a common reservoir during skin and soft tissue infection outbreaks (4–6). Such outbreaks have occurred in community (7–10) settings, e.g., athletic team facilities (11–16), correctional facilities (13,17), and military basic training camps (18,19). Risk factors found in these community settings are frequent skin-to-skin contact (11,12,14,15), sharing of personal items without frequent cleaning (11–14), and MRSA carriage (18,20). Nasal colonization is also a risk factor for infections in hospital settings (4–6,21–23) and long-term care facilities (24,25). However, all of these previous studies have used a case–control study design, making it impossible to determine if MRSA carriage preceded infection.

Little is known about the subsequent risk for skin and soft tissue infections among persons colonized with MRSA. This lack of information becomes a question of clinical significance because increasing numbers of MRSA case-cluster investigations include nasal colonization studies that identify persons as MRSA-colonized. Clinicians and patients are left to consider whether interventions such as decolonization, continued monitoring, or restrictions in occupational activities are indicated. The notable absence of data regarding subsequent risk for illness among MRSA-colonized persons in community settings does little to inform these treatment decisions.

In southwestern Alaska, a dramatic increase in the number of skin infections led to an investigation by the Centers for Disease Control and Prevention and the Yukon Kuskokwim Health Corporation in 2000. MRSA exhibiting the type IV staphylococcal cassette chromosome mec gene had become the predominant community strain in that region, accounting for 100% of S. aureus isolates from skin infections (7,8). Also, the USA400 strain is the predominant strain of CA-MRSA in this area, whereas USA300 is the predominant strain in most other areas of the United States (8). In that initial investigation, we conducted a case–control study in 1 village in Alaska to assess risk factors for MRSA skin infections and evaluated nasal carriage among case–control participants and their household members (1). The present study is a follow-up assessment of participants in the prior nasal colonization survey. Our goal was to assess the risk for subsequent skin infections among persons whose nares cultures were colonized with MRSA (carriers) compared with those colonized with methicillin-susceptible S. aureus (MSSA), or those whose nares cultures were negative for S. aureus (non–S. aureus carriers).


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Suggested Citation for this Article
Stevens AM, Hennessy T, Baggett HC, Bruden D, Parks D, Klejka J. Methicillin-resistant Staphylococcus aureus carriage and risk factors for skin infections, southwestern Alaska, USA. Emerg Infect Dis [serial on the Internet]. 2010 May [date cited]. http://www.cdc.gov/EID/content/16/5/797.htm

DOI: 10.3201/eid1605.090851