Malassezia yeast species isolated from patients with dermatologic lesions

Yeasts of the genus Malassezia form a normal component of skin flora, but are also associated with several dermatological disorders. Since 1996, the description of new species in this genus have led to new questions about their epidemiology and pathogenicity.

Herein, the frequency of Malassezia species in individuals with pityriasis versicolor, atopic dermatitis, seborrhoeic dermatitis, seborrhoeic dermatitis was compared in HIV patients and healthy individuals. Three body sites were selected for examination--head, thorax, and upper and lower extremities.

The 154 Malassezia species were isolated from 112 individuals and grouped as follows: 39 with seborrhoeic dermatitis (20 were HIV-positive patients), 18 with pityriasis versicolor, 18 with atopic dermatitis and 37 without dermatological leisions. HIV patient samples were examined microscopically, and specimens from both patients and healthy subjects were cultured on modified Dixon agar medium. Subsequently, isolates were identified by macroscopic, microscopic and physiological characteristics.

The most commonly isolated species were Malassezia globosa (37.5%), M. sympodialis (31.3%) and M. furfur (31.3%). Malazzerzia globosa predominated in patients with pityriasis versicolor (67%) and in HIV-positive patients with seborrhoeic dermatitis (85%). In non-HIV patients with atopic dermatitis or seborrhoeic dermatitis, M. furfur and M. restricta were isolated in 72% and 26% of the cases, respectively.

Several conclusions were evident. First, Malassezia species was present in subjects with and without dermatological pathologies. Second, the species frequency in the sampled population differed from frequencies reported from other geographic areas. Third, Malassezia globosa was involved at high frequency in patients with dermatological pathologies, suggesting a higher pathogenicity of this species. Additional studies on each species are recommended to clarify their pathogenic roles in association with HIV-positive and normal subjects.