Malassezia pachydermidis

Malassezia pachydermidis - Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath

• Normally present in oily areas on the external ear canal and skin in dogs
  • Some strains have been recovered from the ear canal of cats

• Bottle-shaped, small budding cells, non-mycelial

• Gram stain shows purple yeast cells with a very wide base

• Grows on Sabouraud's Dextrose agar in 2 weeks of incubation at room temperature

• Greenish discolouration on blood agar

• Clinical disease may cause yeast to proliferate and cause infection

• Grossly:
  • Regional lesions: muzzle, ears, interdigital, perianal
  • Or generalised disease
  • Erythematous, hyperpigmented, lichenified and scaly lesions with alopecia

• Microscopically:
  • hyperkeratosis, parakeratosis
  • Spongiotic pustular dermatitis
  • Acanthosis
  • Organisms are usually present- minimum 3-5 yeasts per high-power field must be found to imply cause of disease

• Malassezia pachydermis in malassezia dermatitis