36 – Pathogenic Yeasts Flashcards
Microbiological characteristics: Candida
- Budding yeast
- Incubation of culture in serum for 2 hrs leads to growth of germ tubes
Microbiological characteristics: Cryptococcus
- Produces large mucopolysaccharide capsule
o Capsule is anti-phagocytic and immunosuppressive
Microbiological characteristics: Malassezia
- *bottle shapped cells
- M. pachydermatis: first isolated from Rhino with exfoliative dermatitis
- M. furfur complex fluoresces brick red under UV light
Candida spp: natural host or habitat
- Common in environment and associated with host
- Infections often caused by resident organisms
Malassezia pachydermatis: natural host or habitat
- Found on skin of mammals and birds
- Localized to anatomical sites with lots of sebaceous glands
o Anus, ears, lips, interdigital skin
Cryptococcus spp.: natural host or habitat
- C. gatti: associated with trees and soil
- C. neoformans: droppings of pigeons
- Radiotropic, melanized C. neoformans ID which are hypothesized to utilize ionizing radiation for energy
What does Canadida albicans cause in birds?
- Oral and crop candidiasis
- *most commonly causes infections on the mucous membranes where it is normally found
- *seen in variety of agricultural and pet bird species
What birds are most susceptible to Canadida albicans?
- Young birds
- *outbreaks of disease affecting large proportion of flock
o Sometimes seen as sequelae to coccidiostat treatment (‘flock level procedure’)
What are the clinical signs of Canadida albicans?
- Nonspecific
- Chicks don’t grow, listless
o Signs may be masked by predisposing disease
What are the gross lesions of Canadida albicans in birds?
- Raised, focal thickenings in mucosa of GIT
How do you treat Canadida albicans in birds?
- Possibly treating with in feed nystatin
- Individual bird treatment (topical)
- Possible association with vit A deficiency
o Hypovitaminosis A leading to squamous metaplasia
How do you control Canadida albicans in birds?
- Management (diet, concurrent disease, etc)
- Perhaps: dipping eggs in disinfectant
- Segregate affected birds to protect against cannibalism
What does Canadida albicans cause in horse?
- Superficial infections most common
o THRUSH: on mucous membranes - Systemic candidiasis: OPPORTUNISTIC
o Blood, respiratory tract, joints, urine, etc.
What are the 3 syndromes recognized with Canadida albicans in humans?
- Oropharyngeal
- Genital/vulvovaginal
- Invasive
Oropharyngeal syndrome: Canadida albicans in humans
- White plagues on tongue
- Rare in healthy adults
o AIDS defining condition - Also seen in people with cancer
Genital/vulvovaginal syndrome: Canadida albicans in humans
- Women: vulval pruritus, burning, discharge
- Men: penile pruritic rash
- Wearing cotton underwear may reduce risk of infection
- *affects 75% of all adult women at some point in their lifetime
What are the risks of genital/vulvovaginal syndrome: Canadida albicans in humans?
- Pregnancy
- Diabetes
- Long-term broad spectrum antimicrobials or corticosteroids
Invasive syndrome: Canadida albicans in humans
- *candidemia=increasingly encountered bloodstream infection in hospitalized patients
- Estimated: 25,000 cases annually in US (19-24% mortality)
What does Malassezia pachydermatis cause in dogs?
- Superficial infections in warm, moist anatomic sites
o Interdigital skin
o Lips
o Ear canal
o Groin
o Skin folds
o *erythema, greasy exudate, malodorous exudate - Extensive lesions
o Lichenification (thickened areas of skin)
o Hyperpigmentation - **more common in WARMER MONTHS
How do you treat Malassezia pachydermatis in dogs?
- Topical therapy is VERY IMPORTANT
o Pyoderma: 2% miconazole, 2% chlorhexidine
o Azole containing shampoos (Nizoral)
o Burrow’s solution a very good choice for otitis externa
What is crucial with Malassezia pachydermatis in dogs?
- IDing and controlling underlying disease is CRITICAL
- Ex. atopy, food allergy, endocrinopathy, etc.
What does Cryptococcus gatti cause in cats?
- Most common SYSTEMIC MYCOSIS in cats
o 8x more common than in dogs - Emerged pathogen in Canada
What is are the signs of Cryptococcus gatti in cats?
- Upper respiratory signs
o Sneezing
o Polyp like masses
o Fluctuant subcutaneous swelling on bridge of nose - Neurological signs possible
o Depression, changes in temperament, seizures, circling, head pressing, vestibular disease
What are Cryptococcus gatti and C. neoformans associated with worldwide?
- C. gatti: TREES
- C. neoformans: PIGEON FECES
How do you treat Cryptococcus gatti in cats?
- Azole antifungals
o Itraconazole, fluconazole, voriconazole - Surgical excision of large chunks of fungal infected tissues
- Traumatic flushing
Long term follow up with cats that have/had Cryptococcus gatti
- Long term therapy required
- Can take up to 2 years
- In FeLV/FIV positive cats=may need to treat with antifungals indefinitely
Where does Cryptococcus spp. in humans often infect?
- Lungs: cough, chest pain, fever
- CNS=cryptococcal meningitis: headache, fever, neck pain, nausea
- *requires long term therapy (6+ months)
C. neoformans and people
- Most commonly in people with PRE-existing conditions
o AIDS, organ transplant, immunosuppressive therapy
C. gatti and people
- more likely to affect healthy individuals
- not too common (6-24 cases on an annual basis)
Candida: sample collection and handling
- scrapings
- biopsies in formalin
- milk samples
Malassezia: sample collection and handling
- cytological examination of exudates
- tape strip method
- biopsies
Cryptococcus: sample collection and handling
- tissue for histopathology
- cerebrospinal fluid
- lesions or exudates
Candida: Lab ID
- colony appearance on culture
- microscopy
Malassezia pachydermatis: Lab ID
- microscopy
- culture
Cryptococcus: lab ID
- microscopy of clear fluids
- India ink
Candida: zoonotic/interspecies transmission
- NOT considered zoonotic
Malassezia pachydermatis: zoonotic/interspecies transmission
- NOT a frequent human pathogen
o Rarely reported in people, but don’t bring a therapy dog into a neonatal ICU
Cryptococcus neoformans: zoonotic/interspecies transmission
- NOT spread between individuals who are sick
- Potentially a lab acquired infection
o Make sure to tell the lab if you suspect it
Canadida: treatment options
- Often topical
- Combination of topicals and systemic therapy
o Nystatin orally
o Azoles +/- amphotericin B
Malassezia: treatment options
- Often topical
- Shampoos/topical medications
- Azoles
Cryptococcus spp.: treatment options
- *always SYSTEMIC
- Fluconazole: if fails then itraconazole
- Amphotericine B
