[Isolation and identification of Malassezia spp. In pytiriasis versicolor, seborrheic dermatitis and healthy skin.]

The taxonomy of the genus Malassezia has been recently revised and enlarged to include seven distinct species. The aim of the study was to analyse the prevalence of these species in the cutaneous lesions of pityriasis versicolor and dermatitis seborrhoeica, as well as in the normal skin. Seventy-five patients with pityriasis versicolor, 75 of dermatitis seborrhoeica, and 150 samples of normal skin (75 from the forehead and 75 from the shoulders) were studied. A direct microscopy with KOH + Parker ink was carried out in the pityriasis versicolor and dermatitis seborrhoeica samples. All the samples were inoculated in plates containing modified Dixon medium and incubated at 31 degrees C. The yeasts isolated were identified by its morphological and physiological characteristics, upon the scheme published by Guillot et al. In pityriasis versicolor, Malassezia globosa was found in 84% of cases, alone or associated with Malassezia sympodialis, which was by far the commonest species in normal skin (91.7% of isolates, predominating in the trunk skin). In dermatitis seborrhoeica, Malassezia restricta was the commonest species (63.9%), often associated with M. globosa and/or Malassezia sympodialis. M. globosa was also very common in this disease (54.4%), where Malassezia slooffiae and Malassezia furfur could be detected in less than 5% of the samples. These results support that M. globosa, in its mycelial phase, plays a predominant role in the aetiology of pityriasis versicolor. In dermatitis seborrhoeica, the significance of the presence of different species, mainly M. restricta and M. globosa in its yeast phase, remains unclear. Further studies are needed to establish appropriately the pathogenicity of the lipophilic skin mycoflora.