Yeast-like fungi

FUNGI

Candidosis

• Candidia albicans is the most important species
  • C. tropicalis and C. pelliculosa are other important species

• World wide distribution

• Usually an endogenous mycoses

• Noramlly present on skin, vagina and in the GI tract

• Immunocompromised animals may show symptoms

• Usually lesions on mucous membranes and at mucocutaneous junctions

• Many species have been implicated in bovine mastitis

• C. albicans has been isolated in porcine stomach ulcers

• C. rugosa has been implicated in pyometra in mares

• Infection of the crop, oesophagus and mouth occur in poultry and other birds leading to 'sour crop'
  • White-grey lesions in mouth which adhere loosly to the mucous membrane
  • Crop wall may be thickened
  • Crop wall may be covered by a yellow-white necrotic material
  • Underlying tissue is inflammed

• Causes thrush in humans

• C. albicans causes metritis and vaginitis in mares and genital candidiosis in stallions (and bulls)

• Skin scrapings in 20% KOH for microscopy

• Diphtheritic membranes, pus and fluids can be examined by Lactophenol Cotton Blue and stained by Gram or Methylene Blue

• Gram positive, oval, thin-walled budding cells with hyphal fragments

• Grow on blood agar and Sabouraud's Dextrose agar producing soft, creamy colonies in 24-48 hours

• Grossly:
  • Exudative, papular, pustular to ulcerative dermatitis
  • Stomatitis and otitis externa may develop
• Microscopically:
  • Spongiotic neutrophilic pustular inflammation
  • Parakeratosis
  • Ulcerations
  • Superficial exudate containing organisms

Malassezia pachydermidis

• Caused by Malassezia pachydermatis

• 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

• Grow 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

Rhodotorula

• Rhodotorula minuta and R. rubra

• Canine ear infections

• Equine uterus

• Seldom seen in animal infections

Torulopsis glabrata

• Commensal in animals and is found in the soil

• Implicated in cases of:
  • Pyelonephritis, pneumonia, septicaemia and meningitis (humans)
  • Mastitis and abortion in cattle
  • Systemic infection of monkeys and dogs

Trichosporonosis

• Found in soil

• Deuteromycetes yeast

• Trichosporonosis beigelii
  • Implicated in feline nasal granuloma, skin infections in horses and monkeys, mastitis in cattle and sheep and in feline bladder infections

• T. capitum implicated in bovine mastitis

Further Links

• Mycotic skin infections - Pathology

• Cryptococcus neoformans causes granulomatous rhinitis in cats, see respiratory infections
• Candida is an opportunistic pathogen at mucus membranes, causing thrush.
• Blastomyces dermatitidis in blastomycosis in lungs
• Histoplasma capsulatum in histoplasmosis in lungs
• Candida spp. in candidiasis
• Malassezia pachydermis in malassezia dermatitis