The in vivo effect of UVB radiation on skin bacteria in patients with atopic dermatitis.

Fourteen patients suffering from atopic dermatitis under treatment with UVB radiation were subjected to aerobic bacterial cultures in order to investigate whether this ultraviolet waveband has any in vivo germicidal effects, and, if so, whether there is a correlation with clinical improvement. Treatments were given 3 times a week for 8 weeks. Bacterial samples were collected before, midway and after the termination of therapy. On the latter two occasions, cultures were performed 30 min and 24 h post-UVB irradiation. The main bacteria found were Staphylococcus epidermidis and S. aureus. S. aureus carriage was found in 12 patients in lesional, dermatitic skin, and in 11 patients in clinically non-lesional skin. UVB radiation was found to have an antimicrobial effect primarily concerning S. aureus. Bacterial counts of this organism in lesional skin were decreased from a mean of 1.3 x 10(3) to 1.2 x 10(1) bacteria per cm2 skin at the 8-week 30-min count (p less than 0.01) and 7.5 x 10(1) at the 8-week 24-h count (p less than 0.05). The treatment yielded a statistically significant clinical improvement.