Infectious Dz

Question 1

Histoplasma capsulatum, histologic features of yeast

Answer 1

Yeasts are 2-5 um in diameter, oval to round, with a 1-2 um basophilic center surrounded by a 2 um clear halo (artifact due to cell shrinkage, not a true capsule)
Replication is by narrow-based budding

Question 2

Histoplasmosis histologic lesions

Answer 2

Granulomatous interstitial pneumonia with intrahistiocytic yeast, multinucleated giant cells, +/- caseous necrosis
Non-necrotizing histiocytic/lymphoplasmacytic inflammation with intrahistiocytic yeast in the liver, spleen, lymph nodes, bone marrow, intestinal tract, lungs, adrenal glands, pancreas, eye, skin, heart, kidney, and rarely CNS
Multifocal and coalescing transmural granulomatous inflammation may occur in the stomach, or small and/or large intestine
Macrophages filled with organisms are prominent in the lamina propria, GALT, and/or mesenteric lymph nodes

Question 3

Blastomyces dermatitidis yeast histologic features

Answer 3

Larger (7-15 µm); multinucleated; thick “double contoured” walls; broad-based budding

Question 4

Cryptococcus neoformans

Answer 4

Variably sized yeast (2-20 µm); uninucleate; pleomorphic; single narrow-based budding; mucicarmine-positive capsule; rare hyphae

Question 5

Candida (Torulopsis) glabrata

Answer 5

Slightly larger (2-5 µm); variably sized; oval to elongate; broad-based budding; amphophilic; stain entirely with H&E; no “halo” or pseudocapsule

Question 6

Pneumocystis carinii (jiroveci)

Answer 6

intra-alveolar cyst form: 4-6 µm; primarily extracellular; lacks budding; GMS-positive

Question 7

Sporothrix schenckii

Answer 7

2-6 µm; pleomorphic; single narrow-based budding, thin cell wall; rare hyphae; uninucleate

Question 8

Ophidiomyces ophiodiicola

Answer 8

causative agent of ophidiomycosis, also known as snake fungal disease. This fungus affects captive and wild snakes throughout eastern North America, Europe, and Australia. Clinical signs range from mild to severe crusting dermatitis, deformed scales (arrowhead,Image 3a), subcutaneous nodules, and dysecdysis anywhere on the body, but particularly on the head. Microscopically, hyphae are 2 to 5 μm wide, septate, and parallel-walled, with occasional branching (Image 3b) and cylindrical arthroconidia at the air-epidermis interface (arrowheads,Image 3c).Ophidiomyces ophiodiicolacan also invade deeper tissues and lead to granulomas within the coelom.

Question 9

Basidiobolus ranarum

Answer 9

nonpathogenic fungal infection in reptiles,

Question 10

Nannizziopsis guarroi

Answer 10

cutaneous fungal infection that more commonly affects lizards such as bearded dragons

Question 11

Batrachochytrium dendrobatidis

Answer 11

cutaneous fungal infection that affects amphibians.