Molecular and epidemiologic predictors of Staphylococcus aureus colonization site in a population with limited nosocomial exposure

Background: The anterior naris has been considered the most consistent location of asymptomatic Staphylococcus aureus colonization. However, recent studies have shown that a substantial number of individuals, ranging from 7% to 32% of colonized individuals, are exclusive throat carriers. Most of these studies have been carried out in a health care setting, limiting their generalizability to nonhospitalized populations. Methods: To evaluate anatomic carriage sites of S aureus in individuals outside of a health care setting, we combined the results of 2 cross-sectional studies conducted in Iowa. Results: S aureus was carried by 103 of 340 individuals (30.3%), including 31 (30.1%) exclusive throat carriers, 44 (42.7%) exclusive nose carriers, and 28 (27.2%) colonized in both sites. Nonwhite race (adjusted odds ratio [OR], 4.91; 95% confidence interval [CI], 1.26-18.3) and younger age (≥30 years: OR, 0.23; 95% CI, 0.10-0.54) were associated with increased odds of exclusive throat carriage, whereas nonwhite race (OR, 5.14; 95% CI, 1.62-16.3) and spring or summer sampling season (OR, 2.62; 95% CI, 1.32-5.18) were associated with increased odds of exclusive nasal carriage. Conclusions: These findings suggest that including a throat swab in addition to a nasal swab could play an important role in the success of surveillance programs, particularly among younger adults.