Yeast and Dimorphic Fungal Infections Flashcards
Candida albicans disease type
Opportunistic pathogen - normal flora of the mouth, intestine, lower urogenital tract
“Thrush” - manifests as whitish-yellow hyperkeratoic lesions
Plaques in tongue, mouth, proventriculus, stomach
Candida albicans characteristics
Gram positive staining yeast
Reversibly transitions from single cell to pseudohyphal and hyphal forms
Malassezia pachydermatis
Thick-walled, bottle-shaped, Lipophilic yeast
Commensals on skin of animals
Recognized as a cause of dermatitis - associated with sebaceous glands
Cryptococcus neoformans and Cryptococcus gatti environmental habitats
Cryptococcus neoformans - associated with pigeon droppings
Cryptococcus gattii - eucalyptus tree
Cryptococcus morphology
Large round to oval, budding yeast
Mucopolysaccharide capsule
-prominent in vivo; important virulence factor
Cryptococcus neoformans
Disease of immunocompromised
Chronic granulomatous infection in upper respiratory tract, CNS
Granulomas of nasal cavities when inhaled
Cryptococcus diagnosis
Microscopic detection of encapsulated yeast
Fungal culture
Test for capsular antigen in serum or CSF
Cryptococcus treatment
Long term treatment needed
Continue until serum (CSF serum for CNS disease) antigen negative, or at least one month past resolution of clinical signs
Surgical removal of masses
Cryptoccous prevention
Avoid areas of high concentrations of dried pigeon/bird droppings, areas where there have been disturbances of soil or vegetation (construction, mulching, logging, etc.)
Thermally dimorphic fungi
Single cell (yeast) form at mammalian temperatures (37C) Mold form at ambient environmental temperatures (
Blastomyces characteristics
Characterized by large broad-based budding yeast
Endemic to the Ohio-Mississippi river valley of North America
Environmental organism - associated with proximity to waters
Blastomyces disease
Blastomycosis
Disseminated disease is common
Route of entry is usually by inhalation of spores
Pyogranulomatous, granulomatous host response
Diagnosis of Blastomyces
Large spherical yeast with broad base budding
Histoplasma capsulatum characteristics
Endemic in Ohio, Missouri, and Mississippi river valleys
Grows in abundance in dark, moist soil covered with bird (roosts) or bat droppings (caves)
Histoplasma capsulatum disease
Histoplasmosis
Transmission is favored by dry, dusty conditions and disturbance of soil
Chronic/active respiratory infection
Intestinal disease in common in dogs, but not in humans
Granulomatous inflammation
2nd most common systemic fungal infection in cats
Coccidioides immitis characterisitcs
Dimorphic fungus, but does not produce yeast form, instead large, thick walled spherules containing endospores in tissue
Endemic in San Joaquin valley and southwestern US
Coccidioides immitis disease
Coccidioidomycosis
Entry by inhalation of arthroconidia
Transmission favored by dry conditions and soil disturbance
Chronic/active respiratory and disseminated disease similar to TB
Osteomyelitis is common form of disseminated disease
Diagnosis of Coccidioides immitis
Direct microscopic detection of agent - Spherules containing endospores in the tissues
Sporothrix schenkii characteristics
Cigar-shaped
Fungus lives in sphagnum moss, hay, or other plant material, and soil
Sporothrix schenkii disease
Rose Gardener’s syndrome
Associated with coarse-stemmed, thorny, and woody plants
Disease is usually subcutaneous, restricted to skin nodules
Granulomatous, pyogranulomatous host response
Treatment of thermally dimorphic fungus
Azoles (ketaconazole, itraconazole)
Fungal serology
Beta-D Glucan Assay
- general screening of invasive fungal disease
- false positives and false negatives may occur
Cryptococcus neofmans = Latex agglutination test
-test system for the detect of capsular polysaccharide antigens of Cryptococcus neoformans in serum or CSF (Cryptococcus has a prominent capsule)
