Fungi: Practice Question

Which of the following fungi is found more frequently in the Ohio River valley, Mississippi River valley, St. Lawrence river valley, and is frequently found in dogs?
  1. Blastomyces dermatidis
  2. Coccidioides immitis
  3. Histoplasma capsulatum
  4. Paracoccidioides brasiliensis
  5. Cryptococcus neoformans
Show Answer and Explanations

Blastomyces dermatidis — Correct answer

Correct. Blastomycosis is more commonly found around the Ohio River valley, Mississippi River valley, St. Lawrence river valley, as well as parts of Central and South America and Africa. On culture, the conidia are described as "lollipops." It is unencapsulated and 8 - 20 um in size. Budding is broad based. Infections can be pulmonary, cutaneous or disseminated.

Coccidioides immitis

Incorrect. Coccidioides immitis is found in sands of Mexico and the southwestern U.S., particularly around the San Joaquin Valley. It forms large, thick walled spherules, 10-80 um with endospores. Culture shows alternate staining arthroconidia reminiscent of a chain. Spores are very infectious, but it is not spread from person to person. Primary cutaneous coccidioidomycosis causes erythema multiforme and erythema nodosum. Primary pulmonary coccidioidomycosis (San Joaquin Valley Fever) causes a flu like illness. The disseminated form spreads to the organs.

Histoplasma capsulatum

Incorrect. Histoplasmosis is more commonly found around the Ohio River valley, Mississippi River valley and Missouri River valley, and is associated with bird and bat feces. On culture, microconidia are 2 - 4 um; macroconidia grow later and are 10 -20 um In the body, the organisms are found with macrophages (intracellular yeast).

Paracoccidioides brasiliensis

Incorrect. Paracoccidioides brasiliensis is primarily in South America and causes nasal and pulmonary disease. Yeasts are variable in size at 10-20 um; multiple teardrop and tubular buds stem out from a parent cell, forming the characteristic "pilot wheel" or "mariners wheel."

Cryptococcus neoformans

Incorrect. Cryptococcus is found nearly everywhere in the soil, and is associated with bird feces. It has a thick polysaccharide capsule stainable with India ink (although it is much more commonly diagnosed with antigen based assays in practice). It shows narrow based budding and yeasts of various sizes between 3-20 um. It is urease and inositol positive.

Summary

Summary: Cryptococcus: ubiquitous; bird feces

Paracoccidioides: South America

Histoplasma: Ohio River valley, Mississippi River valley, Missouri River valley; bird and bat feces

Coccidioides: Mexico and the southwestern U.S., sands

Blastomyces: Ohio River valley, Mississippi River valley, St. Lawrence river valley, parts of Central/South America and Africa; dogs
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