A Reappraisal of the Role of Pityrosporum orbiculare in Pityriasis Versicolor and the Significance of Extracellular Lipase

Abstract

Pityrosporum orbiculare is an obligate lipophilic yeast in vitro, which suggests it possesses an extracellular lipase crucial for nutrition. If present in vivo, the enzyme would enable the yeast to utilize skin surface lipids, which may therfore play an important role in the pathogenesis of pityriasis versicolor. Cultured P. orbiculare and biopsy material from patients with pityriasis versicolor were investigated for the presence of lipase by electron microscope histochemistry. At sites of lipase activity, fatty acid hydrolyzed from Tween 80 substrate reacts with Ca++ ions to form an insoluble Ca++ soap. Exchange of Ca++ with Pb++ enables the sites of lipase activity to be visualized as electron dense deposits of insoluble lead soap. Surface lipase activity was apparent when the technique was applied to P. orbiculare grown on lipid containing medium and its specificity confirmed by removal of substrate and inhibition by di-isopropyl fluorophosphate and quinine hydrochloride, but not by sodium fluoride. When the same technique was applied to stratum corneum infected with Pityrosporum furfur (Malassez), no reaction product could be detected. It is postulated that lipase, although critical for fungal nutrition in vitro, is unlikely to be of importance in vivo. Skin surface lipids are therefore probably not relevant to the pathogenesis of pityriasis versicolor.

Selective and Differential Media for Isolation and Tentative Identification of Each Species of Pityrosporum Residing on Normal or Diseased Human Skin

“…Among these organisms, P. ovale and P. orbiculare have been considered as resident microorganisms of the normal human skin and also as pathogenic agents of tinea versicolor (4,8,17,18), dermatitis seborrheica (17), comedones (21), and folliculitis (10).…”

Immunology of Diseases Associated withMalasseziaSpecies

“…They have lipolytic activity both in vitro (301,459) and in vivo (85,272), indicating the production of a lipase. The lipase is located in the cell wall and/or membrane sites in the cytoplasm (85,349).…”

“…They have lipolytic activity both in vitro (301,459) and in vivo (85,272), indicating the production of a lipase. The lipase is located in the cell wall and/or membrane sites in the cytoplasm (85,349). Ran et al (349) found that the pH optimum was 5.0 and that lipase production was greatest during the logarithmic phase of growth, perhaps demonstrating its importance in the hydrolysis of lipids for cell growth.…”

MfLIP1, a gene encoding an extracellular lipase of the lipid-dependent fungus Malassezia furfur

“…Besides their important role in biotechnology, these reactions have been discussed as potential virulence factors in pathogenic bacteria and fungi. Other studies have demonstrated the ability of M. furfur to release fatty acids from different lipids (Catterall et al, 1978;Hammer & Riley, 2000;Mancianti et al, 2001). Ran et al (1993) did not detect lipases in the supernatant, but determined that the main lipolytic activity was in the insoluble fraction of cell extracts.…”