Objective: To study the prevalence of Staphylococcus aureus colonization in close contacts of patients with atopic dermatitis (AD) and the influence on AD severity.
Design: Prospective case-control study.
Setting: Pediatric dermatology clinic in a Hong Kong university hospital. Patients We recruited 211 subjects prospectively, including 50 AD patients, 50 non-AD control subjects, 60 close contacts of AD patients, and 51 close contacts of controls. Intervention Nasal swabs and skin swabs were taken. Severity of AD was assessed using the SCORAD (Scoring Atopic Dermatitis) index.
Main outcome measures: The prevalence of S aureus colonization in the close contacts of AD patients was compared with that of the close contacts of non-AD controls. Between-group differences were assessed, where appropriate, by unpaired t test or Pearson chi(2) test. Multivariate logistic regression using the forward stepwise method was performed to identify independent predictors of severe AD. A probability value of P < .05 was considered statistically significant.
Results: Significantly more nasal carriers of S aureus were found among the close contacts of AD patients (14 of 60 [23%]) than among the close contacts of non-AD controls (4 of 51 [8%] [P = .03]). The difference was still significant after the exclusion of the AD patients' close contacts who also had AD (24% vs 8% [P = .03]). By multivariate analysis, only skin colonization of S aureus was independently associated with severe AD (odds ratio, 17.0; 95% confidence interval, 1.60-181.1 [P = .02]).
Conclusions: Anterior nares of close contacts of AD patients are reservoirs of S aureus. The presence of S aureus carriers among close contacts does not predict AD severity. Skin colonization is associated with severe AD.