Assessment of a contact-plate sampling technique and subsequent quantitative bacterial studies in atopic dermatitis

The aerobic bacterial flora of 20 patients with atopic dermatitis and 19 control subjects was extensively sampled using the Williamson and Kligman scrub technique and a contact-plate method (cysteine lactose electrolyte deficient media). Comparison of the two quantitative techniques showed that the contact plate is a reliable and convenient alternative to the scrub technique for the quantification of Staphylococcus aureus, micrococci and coagulase negative staphylococci. Quantification of bacterial flora using both techniques showed high rates of colonization by S. aureus on both involved and clinically normal skin of patients with atopic dermatitis. A linear increase in S. aureus counts with increasing severity of dermatitis was found. In contrast, diphtheroids showed a trend of decreasing isolation rates and counts as the severity of the dermatitis increased. Isolation rates and absolute counts for micrococci/coagulase negative cocci were unaffected by the severity of the dermatitis.