Staphylococcus aureus-derived enterotoxins enhance house dust mite-induced patch test reactions in atopic dermatitis

Background: Up to 65% of Staphylococcus aureus strains isolated from the skin of patients with atopic dermatitis (AD) produce exotoxins with superantigenic properties that may also act as allergens leading to an induction of exotoxin-specific IgE antibodies. Staphylococcal enterotoxin B (SEB) applied epicutaneously in a concentration of 10 mu g/cm(2), i.e. 200 mu g/ml, under occlusion induces cutaneous inflammation in patients with AD and healthy individuals. Methods: We performed patch tests in 32 adult patients with AD using different concentrations (i.e. 2-200 mu g/ml) of SEA, SEB and house dust mite (HDM) extract (500 mu g/ml). Furthermore, the respective enterotoxins and HDM extract were applied simultaneously to the same patch test site. Specific IgE levels to SEA, SEB and HDM were measured with the CAP FEIA. Results: The rates of patch test reactions to SEA and SEB increased with rising enterotoxin concentrations. There were no differences in the rates of patch test reactions to SEA and SEB between patients sensitized to the corresponding enterotoxin and non-IgE-sensitized patients. The number of patch test reactions to the mixture of enterotoxin and HDM extract was higher than the number of patch test reactions to either the enterotoxins or HDM extract. We identified 11 patients with AD who reacted neither to the enterotoxins nor to HDM extract, but who showed patch test reactions to the mixture. These reactions were not predicted by the presence of enterotoxin- or HDM-specific IgE. Conclusions: Colonization with exotoxin-producing S. aureus may influence the outcome of patch tests in patients with AD.