Identification and pathogenicity of Malassezia species isolated from human healthy skin and with macules

Abstract

This study investigated the ocurrence of Malassezia species in clinically healthy students and with macules with a slight fawn discoloration and characterized the isolates as to the pathogenicity factors such as growth at 37ºC, lipase, phospholipase and protease detection. Clinical samples were collected from different body sites of one hundred students of different ages and both sexes. The samples, obtained by scrapping the skin surface and the scalp, were treated with potassa and cultured. Cultures were obtained in Petri dishes containing Sabouraud agar medium added of olive oil, incubated at room temperature and at 37ºC. Culture identifications were based in their morphological and physiological properties. Lipase, phospholipase and protease detection was performed in specific media on Petri dishes for formation of a zone. Globose, spherical yeast cells and hypha were investigated by direct microscopy of clinical materials. Malassezia furfur was detected in seven samples and M. sympodialis in four. All Malassezia cultures presented lipase activity, but none was phospholipase positive. Protease activity was observed in two M. furfur and two M. simpodialis isolates. Key words: Malassezia furfur, M. simpodialis, pathogenicityMalassezia is a lipophilic yeast frequently found in normal human skin. Current evidence indicates a high rate of skin colonization in healthy adults, in contrast with the low rate of colonization in prepubertal children (20).Gueho et al. (11) (14,17,35,38). With the exception of M. pachidermatis, the remaining eight species have an absolute in vitro requirement for suplementation of long-chain fatty acids. Based on studies conducted within the last 5 years, it appears that the most frequently organism associated with pityriasis versicolor may not be M. furfur and possible candidates include M. globosa (2,27) and M. sympodialis (15). The genus Malassezia was recently revised, but the clinical significance of each of these species is not clearly understood (15).Pityriasis versicolor (tinea versicolor) is a superficial fungal infection of the skin, appearing most commonly on the upper trunk, as well as on the upper arms, neck and face. As suggested by its name, pityriasis versicolor may be manifested in different colours, ranging from pink or to dark brown or even black. The lesions have a characteristic flaking appearance, although in larger lesions this can be evident only at the border of the macule, and can be hypopigmented or hyperpigmented. Generally, the lesions take the form of round or oval macules or papules, although in advanced cases the lesions may become confluent (13,21,33).

Overview on the Fungal Metabolites Involved in Mycopathy

“…Lipase is another enzyme associated with the pathogenicity of Malassezia furfur that cause pityriasis versicolor. This association is showed by studies of Neves et al [149] on Table 2. Enzymes produced by some pathogenic fungi and their roles in pathogenesis.…”

Antifungal activities of azole agents against the Malassezia species

“…between geographical regions. Malassezia globosa is predominant in the two extremes of southern Europe [13], M. sympodialis is the most common species in Canada [14], whilst in Brazil M. furfur was found highly associated with skin macules [15]. Despite the fact that the broth microdilution method recommended by the NCCLS is generally accepted as a standard protocol to determine yeast susceptibility, this technique should be slightly adapted for Malassezia spp.…”