So far in this series we have covered the main human pathogenic yeasts: Candida spp. (and species previously in the genus Candida), Cryptococcus spp. and Pneumocystis jirovecii

In this episode we will talk about some less common yeast pathogens: Malassezia spp., Rhodotorula ssp., Trichosporon spp. and Saccharomyces spp.

Malassezia spp.

• Malassezia spp. are basidiomycetes and part of our normal skin flora
• The genus includes 16 species - these include:
  • M. furfur
  • M. globosa
  • M. sympodialis
  • M. restricta
• A range of skin conditions are associated with Malassezia spp., including pityriasis versicolor, seborrheic dermatitis, dandruff, atopic eczema and folliculitis.
• 15 of the 16 species are lipid-dependent – only grow in the presence of certain fatty acids

Clinical features

Skin manifestations

Malassezia may cause or exacerbate a variety of common skin conditions

These are usually seen and managed in primary care or by dermatology and include:

• Pityriasis versicolor = superficial skin infection characterised by hypopigmented lesions (non-itchy) usually confined to trunk and proximal limbs
  • Usually caused by Malassezia globosa or Malassezia furfur
• Malassezia folliculitis = small, itchy papules/pustules at hair follicles, particularly on the back and upper chest
• Seborrhoeic dermatitis and dandruff = common, chronic dermatitis involving oily (sebaceous gland-rich) regions of the scalp, face and trunk
  • Cradle cap in infants

Predisposing factors to skin disease include: humidity, sweating, oily skin, immunodeficiency / immunosuppression

Pityriasis versicolor

Malassezia folliculitis

Invasive infection

• Malassezia spp. can rarely cause fungaemia