[Isolation and identification of Malassezia spp. In pytiriasis versicolor, seborrheic dermatitis and healthy skin.]. / Aislamiento e identificación de Malassezia spp. en pitiriasis versicolor, dermatitis seborreica y piel sana.

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.

Malassezia globosa as the causative agent of pityriasis versicolor.

BACKGROUND: The taxonomic revision carried out in 1996 on the genus Malassezia, which now comprises seven different species, made necessary a re-evaluation of the data concerning the ecology and pathogenicity of these lipophilic yeasts. Very little has been published since then. OBJECTIVES: The aim of this work was to contribute to the knowledge of the aetiology of pityriasis versicolor (PV) with a mycological study made according to the new species. METHODS: Ninety-six patients with PV completed the study. In all of them, samples were taken from the lesions for direct microscopy with KOH+ Parker ink and culture. Samples were also taken from normal skin of the trunk and the forehead of the same patients for culture. Cultures were made in modified Dixon medium in Petri dishes, incubated at 31 degrees C and the isolates were identified by morphological and physiological characteristics. RESULTS: In the PV lesions, direct microscopy always showed the typical mixture of globose blastoconidia and pseudomycelium. Only one patient, having received previous topical antimycotic treatment, was negative. The spherical yeasts observed in vivo were morphologically identical to the globose yeasts characteristic of M. globosa. In culture, M. globosa was found in 97% of cases, alone in 60% of them and associated with M. sympodialis in 29% and M. slooffiae in 7%. These two species were also found in similar percentages on the clinically uninvolved skin of the trunk, whereas M. globosa was not isolated at these sites. However, on the forehead, a small number of colonies of M. globosa was recovered in 12% of cases. CONCLUSIONS: These results support the data previously reported and strongly suggest that M. globosa in its mycelial phase is the causative agent of PV.

Carcinoma epidermoide de pene. Estudiomediante hibridación in situ / Epidermoid carcinoma of the penis. An in situ hibridisation study

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