Difference between revisions of "Yeast-like fungi"

From WikiVet English
Jump to navigation Jump to search
Line 137: Line 137:
 
==''Malassezia pachydermidis''==
 
==''Malassezia pachydermidis''==
 
[[Image:Malassezia pachydermidis.jpg|thumb|right|150px|''Malassezia pachydermidis'' - Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath]]
 
[[Image:Malassezia pachydermidis.jpg|thumb|right|150px|''Malassezia pachydermidis'' - Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath]]
*Caused by [[Fungi|''Malassezia pachydermatis'']]
+
*Normally present in oily areas on the external [[The Ear - Anatomy & Physiology|ear]] canal and [[Skin - Anatomy & Physiology|skin]] in dogs
 
+
**Some strains have been recovered from the [[The Ear - Anatomy & Physiology|ear]] canal of cats
*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
 
*Bottle-shaped, small budding cells, non-mycelial
Line 146: Line 144:
 
*Gram stain shows purple yeast cells with a very wide base
 
*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
+
*Grows on Sabouraud's Dextrose agar in 2 weeks of incubation at room temperature
  
 
*Greenish discolouration on blood agar
 
*Greenish discolouration on blood agar
  
 
*Clinical disease may cause yeast to proliferate and cause infection
 
*Clinical disease may cause yeast to proliferate and cause infection
 +
 
*Grossly:
 
*Grossly:
**Regional lesions: muzzle, ears, interdigital, perianal
+
**Regional lesions: muzzle, [[The Ear - Anatomy & Physiology|ears]], interdigital, perianal
 
**Or generalised disease
 
**Or generalised disease
 
**Erythematous, hyperpigmented, [[Skin Glossary - Pathology|lichenified]] and scaly lesions with alopecia
 
**Erythematous, hyperpigmented, [[Skin Glossary - Pathology|lichenified]] and scaly lesions with alopecia
 +
 
*Microscopically:
 
*Microscopically:
 
**[[Skin Glossary - Pathology|hyperkeratosis, parakeratosis]]
 
**[[Skin Glossary - Pathology|hyperkeratosis, parakeratosis]]
 
**Spongiotic pustular dermatitis
 
**Spongiotic pustular dermatitis
 
**[[Skin Glossary - Pathology|Acanthosis]]
 
**[[Skin Glossary - Pathology|Acanthosis]]
**Organisms are usually present, minimum 3-5 yeasts per high-power field must be found to imply cause of disease
+
**Organisms are usually present- minimum 3-5 yeasts per high-power field must be found to imply cause of disease
  
 
*''Malassezia pachydermis'' in [[Mycotic skin infections - Pathology#Malassezia dermatitis|malassezia dermatitis]]
 
*''Malassezia pachydermis'' in [[Mycotic skin infections - Pathology#Malassezia dermatitis|malassezia dermatitis]]

Revision as of 20:23, 28 April 2009



Infectious agents and parasitesWikiBugs Banner.png
FUNGI



Candidosis

Sour Crop - Copyright Professor Andrew N. Rycroft, BSc, PHD, C. Biol.F.I.Biol., FRCPath
  • Candidia albicans is the most important species
    • C. tropicalis and C. pelliculosa are other important species
  • World wide distribution
  • Usually an endogenous mycoses
  • 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 stain
  • 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

Cryptococcosis

  • Over 19 species
    • C. neoformans only major pathogen
  • Worldwide
  • Occurs in high concentrations in pigeon droppings (high creatinine concentration)
    • The pigeon is not infected
    • C. neoformis colonise the droppings after they have been excreted
    • Also found in fruit, milk and soil
  • Exogenous, inhaled infection which is generally sporadic (non-contageous)
    • Can also be absorbed via skin penetration and ingestion
  • May be a primary pathogen or opportunistic
  • Causes sporadic mastitis in cattle
    • Can spread within the herd
  • Affects the CNS of dogs and cats
  • Causes myxoma-like lesions of the lung and lip in horses
  • Causes cryptococcal meningitis in humans
  • Also affects dolphins, foxes, ferrets, monkeys, birds, cheetahs and guinea-pigs
  • Large yeast with capsule seen using India ink stain
  • Stains with PAS (Periodic acis Schiff)
  • Gram positive
  • Grows on blood agar and Sabouraud's Dextrose agar forming white, granular colonies which become slimy, mucoid and turn creamy/brown within a week
  • Species identified by carbohydrate assimilation tests
  • Antigen and antibody should be tested for as antibody formed by the body is soon overwhelmed and neutralised by abundent polysaccharide antigen from the capsule in active, systemic infections
    • Latex agglutination for antigen, complement fixation, ELISA and IFAT can be used

Geotrichosis

  • G. candidum
  • Rare
  • Two forms: the yeast-like (glaborous) and fluffy
  • Affects a wide range of species
  • Usually diagnosed post-mortem
  • Usually mild, causing suppurative granulomas
  • Can be recovered from otitis externa infections in dogs
  • Organisms appear as rectangular or spherical arthrospores on wet mounts
    • Thick walled, non-budding, gram positive
  • Grow on Sabouraud's Dextrose agar
    • Membranous colonies
    • Do not grow well on blood agar

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:

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