Malassezia pachydermidis

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

Malassezia pachydermidis is commonly found on healthy skin and mucosa. It is an opportunistic pathogen of both cats and dogs, and during infection it may increase 100-10000 fold on the skin. It is most commonly recovered from the ear, anus, and the paws.

Some breeds are more predisposed than others, with Dachshunds and Cocker spaniels amongst the most commonly seen. M. pachydermidis is seen concurrently with a Staphylococcus intermedius infection.

Hot, humid conditions favour the development of the infection.

• 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