Role of Home Environmental Staphylococcus Aureus Bacterial Allergens in Childhood Asthma
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
Meghan F. Davis, DVM, MPH, PhD, Shanna Ludwig, PhD, Emily Brigham, MD, Meredith C. McCormack, MD, Elizabeth Matsui, MD MHS
Rationale: Staphylococcus aureus (SA) may induce allergic (Th2-biased) inflammatory responses through secreted staphylococcal enterotoxin (SE) A-D superantigens. SA is known to exacerbate eczema and increasingly is implicated in asthma exacerbations. We quantified putative staphylococcal allergens in home dust using a bacterial genetic method, then we associated SA/SE exposures with respiratory symptoms among children with asthma.

Methods: We measured SA (femB) and SEA-D genes in home dust extracts from the randomization visit (before treatment) in the completed Asthma Control Evaluation cohort (NCT00114413) using real-time PCR. We tested cross-sectional associations between dust exposures and self-reported respiratory symptoms in 245 inner-city children with asthma (~50% of the cohort) using linear and binomial regression modeling.

Results: We identified SA genes in 189 (77%) of 245 homes, with prevalence of any SE gene detection as follows: SEA (60%); SEB (52%); SEC (51%); SED (63%). Among children with asthma, mean ACT score was 20.7 and mean days of symptoms in the prior two weeks were: wheeze/cough: 2.2; interference with activities: 1.2; sleep disruption: 0.6. Strong dust SEA detection, i.e. threshold cycle (Ct)≤35, was associated with worse ACT score [β=-1.46, p=0.01] and increased odds of having a symptom day for each of the two-week outcomes, e.g. [wheeze/cough OR 1.55, p<0.001]. SA and SEB-SED were variably associated or were not associated with respiratory symptom outcomes.

Conclusions: Home staphylococcal dust exposures (SA/SE) were common among inner-city children with asthma. Dust SEA detection consistently was associated with increased respiratory symptoms in this cohort. Longitudinal studies are needed to confirm and explicate this novel finding.