Nasal carriage of Staphylococcus aureus among patients receiving allergen-injection immunotherapy: associated factors and quantitative nasal cultures.

OBJECTIVE: To compare the prevalence of nasal Staphylococcus aureus carriage among outpatients receiving allergen-injection immunotherapy with the prevalence among healthy controls and to determine predictors of nasal S. aureus carriage. DESIGN: Survey. SETTING: Allergy clinic of a university hospital. PARTICIPANTS: A volunteer sample consisting of 45 outpatients undergoing desensitization therapy and 84 first- and second-year medical students. RESULTS: The nasal S. aureus carriage rate was significantly higher among patients (46.7%) than among students (26.2%; P=.019). In a multivariate model adjusted for age and gender, the presence of atopic dermatitis or eczema was the only independent predictor of nasal S. aureus carriage (odds ratio OR], 4.4; 95% confidence interval CI95], 1.2-16.0; P=.02). The only other participant characteristic associated with nasal S. aureus carriage was immunotherapy with allergen injections (OR, 1.98; CI95, 0.7-6.0), but this association did not reach statistical significance (P=.23). The probability of nasal S. aureus carriage was 88.9% for patients receiving allergen injections and having atopic dermatitis or eczema, and 36.1% for patients receiving allergen injections without atopic dermatitis or eczema. CONCLUSIONS: Patients undergoing desensitization have a higher nasal carriage rate of S. aureus. However, factors other than the regular use of needles, and in particular abnormalities related to the atopic constitution of these patients, may predispose this population for S. aureus carriage.