Quantitative culture of Malassezia species from different body sites of individuals with or without dermatoses

Abstract

Quantitative cultures were obtained using contact plates to determine whether the quantity and composition of Malassezia species at a given anatomic site in normal individuals differs from that of patients with various cutaneous dermatoses. The sample included 20 clinically healthy individuals (without any dermatosis) and 110 patients with dermatoses (including 31 with atopic dermatitis [AD], 28 with psoriasis [PS], 28 with seborrheic dermatitis [SD] and 23 with pityriasis versicolor [PV]). Contact plates filled with special culture medium were used to obtain a quantitative culture from five body sites (scalp, forehead, arm, trunk and leg) of every individual. The number of cfu were recorded for every plate that grew Malassezia yeasts, and 3-5 colonies were isolated for identification to species level using microscopic, physiological and molecular characteristics. The mean cfu counts observed among patients with AD, PS and SD was significantly lower than normal control subjects (P < 0.05). The mean cfu counts from PV patients was not different from that of healthy control subjects. Overall, for all conditions considered together, the mean cfu counts in lesional sites were significantly lower than in non-lesional sites (P <0.05). Furthermore, the mean cfu counts from lesional sites in patients with AD and PS were significantly lower than the corresponding value in patients with PV (P <0.05). Six Malassezia species were recovered from the different dermatoses. Malassezia sympodialis was the most common species associated with AD and PV patients and healthy control subjects, while M. globosa was most frequently isolated from PS and SD patients. More than one Malassezia species was recovered at any given anatomic site from both controls as well as individuals with dermatoses. M. globosa was equally likely to be recovered from scalp, forehead and trunk, but less likely to derive from arms and legs. M. restricta and M. slooffiae were recovered more frequently from the upper body (scalp and forehead) than from the lower body. Among normal individuals and for patients with AD and PV, M. sympodialis was significantly more likely to affect the forehead than the legs.