Nasal carriage of methicillin-resistant Staphylococcus aureus in an American Indian population

Abstract

Background and objective: Although reports of methicillin-resistant Staphylococcus aureus (MRSA) infections without healthcare exposure are increasing, population-based data regarding nasal colonization are lacking. We assessed the prevalence of and risk factors for community-associated MRSA nasal carriage in patients of a rural outpatient clinic.

Design: A cross-sectional population survey was conducted through random sample and stratification by community of residence. Recent healthcare exposure (ie, hospitalization, dialysis, or healthcare occupation) and other risk factors for MRSA carriage were assessed. Cultures of the nares were performed. Community-associated MRSA was defined as MRSA carriage without healthcare exposure.

Setting: A predominantly American Indian community in Washington.

Patients: Those receiving healthcare from an Indian Health Service clinic.

Results: Of 1,311 individuals identified for study, 475 (36%) participated. Unsatisfactory culture specimens resulted in exclusion of 6 participants. In all, 128 (27.3%) of 469 participants had S. aureus. Nine (1.9%) of 469 had MRSA carriage; of these, 5 had community-associated MRSA (5 of 469; overall community-associated MRSA carriage rate, 1.1%). MRSA carriage was associated with antimicrobial use in the previous year (risk ratio [RR], 7.2; P = .04) and residence in a household of more than 7 individuals (RR, 4.5; P = .03). Pulsed-field gel electrophoresis indicated that 5 (55%) of 9 MRSA carriage isolates were closely related, including 3 (60%) of 5 that were community associated.

Conclusions: Prevalence of community-associated MRSA colonization was approximately 1% in this rural, American Indian population. Community-associated MRSA colonization was associated with recent antimicrobial use and larger household.