Yeast and Dimorphic Fungal Infections

Question 1

Candida albicans disease type

Answer 1

Opportunistic pathogen - normal flora of the mouth, intestine, lower urogenital tract
“Thrush” - manifests as whitish-yellow hyperkeratoic lesions
Plaques in tongue, mouth, proventriculus, stomach

Question 2

Candida albicans characteristics

Answer 2

Gram positive staining yeast

Reversibly transitions from single cell to pseudohyphal and hyphal forms

Question 3

Malassezia pachydermatis

Answer 3

Thick-walled, bottle-shaped, Lipophilic yeast
Commensals on skin of animals
Recognized as a cause of dermatitis - associated with sebaceous glands

Question 4

Cryptococcus neoformans and Cryptococcus gatti environmental habitats

Answer 4

Cryptococcus neoformans - associated with pigeon droppings

Cryptococcus gattii - eucalyptus tree

Question 5

Cryptococcus morphology

Answer 5

Large round to oval, budding yeast
Mucopolysaccharide capsule
-prominent in vivo; important virulence factor

Question 6

Cryptococcus neoformans

Answer 6

Disease of immunocompromised
Chronic granulomatous infection in upper respiratory tract, CNS
Granulomas of nasal cavities when inhaled

Question 7

Cryptococcus diagnosis

Answer 7

Microscopic detection of encapsulated yeast
Fungal culture
Test for capsular antigen in serum or CSF

Question 8

Cryptococcus treatment

Answer 8

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

Question 9

Cryptoccous prevention

Answer 9

Avoid areas of high concentrations of dried pigeon/bird droppings, areas where there have been disturbances of soil or vegetation (construction, mulching, logging, etc.)

Question 10

Thermally dimorphic fungi

Answer 10

Single cell (yeast) form at mammalian temperatures (37C)
Mold form at ambient environmental temperatures (

Question 11

Blastomyces characteristics

Answer 11

Characterized by large broad-based budding yeast
Endemic to the Ohio-Mississippi river valley of North America
Environmental organism - associated with proximity to waters

Question 12

Blastomyces disease

Answer 12

Blastomycosis
Disseminated disease is common
Route of entry is usually by inhalation of spores
Pyogranulomatous, granulomatous host response

Question 13

Diagnosis of Blastomyces

Answer 13

Large spherical yeast with broad base budding

Question 14

Histoplasma capsulatum characteristics

Answer 14

Endemic in Ohio, Missouri, and Mississippi river valleys

Grows in abundance in dark, moist soil covered with bird (roosts) or bat droppings (caves)

Question 15

Histoplasma capsulatum disease

Answer 15

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

Question 16

Coccidioides immitis characterisitcs

Answer 16

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

Question 17

Coccidioides immitis disease

Answer 17

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

Question 18

Diagnosis of Coccidioides immitis

Answer 18

Direct microscopic detection of agent - Spherules containing endospores in the tissues

Question 19

Sporothrix schenkii characteristics

Answer 19

Cigar-shaped

Fungus lives in sphagnum moss, hay, or other plant material, and soil

Question 20

Sporothrix schenkii disease

Answer 20

Rose Gardener’s syndrome
Associated with coarse-stemmed, thorny, and woody plants
Disease is usually subcutaneous, restricted to skin nodules
Granulomatous, pyogranulomatous host response

Question 21

Treatment of thermally dimorphic fungus

Answer 21

Azoles (ketaconazole, itraconazole)

Question 22

Fungal serology

Answer 22

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)