METHODS: We measured SA (femB) and SEA-C genes in home dust using real-time PCR and cultured nasal swabs in an ongoing cohort (NCT02251379) of 5-17yo African-American children with asthma. We tested associations between environmental staphylococcal exposures and respiratory symptoms and lung function in 48 children across 50 home visits. Models adjusted for SA colonization, allergic sensitizations, mouse/cockroach allergen concentrations, household smoking, demographics, and repeated observations within participants.
RESULTS: All homes had detectable SA, with a median of 5.7x105 gene copies per gram of dust [25th-75th %iles: 2.4x105-4.1x106]. Detection of SE genes was: SEA 30%, SEB 77%, SEC 50%. Detection of SA nasal colonization was 67%. Increasing concentrations of the SA gene (femB) were associated with 10-fold higher odds of having a FEV1/FVC ratio <80% (p<0.002) and 5.9-fold higher odds of having a 12%+ improvement in FEV1 after albuterol treatment (p<0.02) but were not associated with increased symptoms. Detection of SEB, but not other SEs, was associated with 3.8-fold higher odds of having a day with activities slowed by asthma (95% CI: 1.34-10.6, p<0.02), and 100% of patients with asthma-related speech impairment were exposed to SEB. SEB exposure typically was associated with increased frequency of other symptom outcomes, but these were not statistically significant.
CONCLUSIONS: Home dust exposures to SA and SEB, independent of SA nasal colonization, may worsen existing asthma among inner-city children.