Staphylococcus aureus:: colonizing features and influence of an antibacterial treatment in adults with atopic dermatitis

Background The skin of up to 100% of patients with atopic dermatitis (AD) is colonized with Staphylococcus aureus . Of all S. aureus strains isolated from lesional skin, up to 65% have been shown to produce exotoxins with superantigenic properties. Patients colonized with S. aureus have been treated with antibiotics in several open and double-blind placebo-controlled studies, with conflicting results. These studies did not consider the anterior nares as a reservoir of S. aureus , or the possibility of transmission between patients and their contacts. Moreover, adult patients have not so far been investigated. Objectives To investigate the colonizing features of S. aureus in adults with AD and in their contacts, and the effect of an antimicrobial treatment of the patients and their partners. Methods Swabs were taken from the skin and anterior nares of 66 adults with AD. S. aureus strains were screened for the production of exotoxins in 32 patients. Ten patients (two with toxigenic strains, eight with non-toxigenic strains) were treated orally with cefalexin, chlorhexidine ointment was applied to the skin, and the anterior nares were treated with mupirocin ointment. A bath containing potassium permanganate was taken daily. In addition, their partners were treated topically. Results Sixty-two of 66 patients (94%) were carriers of S. aureus , and mostly harboured the bacteria on both skin and anterior nares. Ten of 32 (31%) patients were colonized with toxigenic strains. The Severity Scoring in AD (SCORAD) score decreased in nine of 10 patients who received antimicrobial treatment (P < 0.001), and this effect was more pronounced in patients with a baseline SCORAD > 50. Conclusions S. aureus may play an important role as an aggravating factor in adults with AD, as antimicrobial treatment leads to a significant improvement of AD in patients who are colonized with the bacterium.