Fungi

Question 1

Inhibition of synthesis of ergosterol. Why is it important?

Answer 1

Imidazole

Major membrane sterol

Question 2

Dimorphic fungi. Form at different temperature

Answer 2

Histoplasma 
Blastomyces
Coccidiodes
Sporothrix
- cold ▶️ mold (hyphae)
- warm ▶️ yeast

Question 3

Uses of silver stain

Answer 3

Pneumocystis ▶️ gray to black

Question 4

Uses of India Ink preparation on CSF sediment

Answer 4

Rules in Cryptococcus neoformans

*low sensitivity (misses 50%)

Question 5

What technique can you use to detect fungal antigen in CSF, serum? Example

Answer 5

Latex particle agglutination or counter immunoelecfrophoresis.
Cryptococcal capsular polysaccharide

Question 6

Which organism in KOH with yeast clusters and curved septate hyphae “spaghetti and meatballs”? Disease.

Answer 6

Malassezia furfur

Pityriasis or tinae versicolor

Question 7

Dermatophytes (genus) that cause the Tinaes. Diagnosis.

Answer 7

Trichophyton ▶️ skin, hair, nails
Microsporum ▶️ hair, skin
Epidermophyton ▶️ nails, skin
- KOH (nail or skin scraping) ▶️ arthroconidia, hyphae
- microsporum ▶️ fluoresces bright yellow-green (wood lamp)

Question 8

Rose gardener, florist or basket weaver individual with cigar-shaped yeast in KOH of skin. Disease, microbial agent and presentation.

Answer 8

Sporotrichosis
Sporothrix schenckii
Subcutaneous or lymphocutaneous lesion (mycetoma)

Question 9

Environmental and tissue form of histoplasmosis, which is useful for diagnosis. Endemic region.

Answer 9

• environmental: hyphae + microconidia, and macroconidia
• tissue: multiple intracellular yeasts ▶️ Dx
• Great Lakes (East) to Gulf of Mexico

Question 10

Why can you find hepatosplenomegaly in histoplasmosis?

Answer 10

Facultative intracellular in Reticuloendothelial system (RES) cells

Question 11

Clinical presentation of coccidioides immitis and how do you diagnose it? How is the transmission?

Answer 11

• Valley fever ▶️ Immunocompetent ▶️asymptomatic self-resolving pneumonia, erythema nodosum, arthritis.
• Immunocompromised ▶️ chronic calcifying lesion at lung, nodules and cavities, dissemination (meningitis or mucocutaneous)
• Spherules containing endospores in tissue (lung at body temperature), history of endemic area
• Hyphae (fragmentation) ▶️ spores inhalation ▶️ transmission

Question 12

Diagnose and endemic region of blastomyces dermatitidis. Suspected exposure associated.

Answer 12

• sputum ▶️ broad-base, budding yeast with double refractile cell wall
• North, South Carolina, upper Great Lakes, Ohio, Mississippi River beds, southern, northern Minnesota to Canada
• rooting wood (beaver dams)

Question 13

Predisposing conditions and their respective diseases that aspergillus fumigatus can cause.

Answer 13

• Asthma, cystic fibrosis ▶️ allergic bronchopulmonary aspergillosis
• Previous cavitary lesion ▶️ fungus ball
• Burns, CGD, CF, severe neutropenia ▶️ cellulitis, may disseminate

Question 14

Infection in IV drug abusers by aspergillus

Answer 14

Endocarditis

Question 15

Major predisposing condition in aspergillosis, which are the infections with that association?

Answer 15

Antibiotic use and immunocompromised host

Oral thrush, esophagitis, gastritis, septicemia

Question 16

Dominant cause of meningitis AIDS patients

Answer 16

Cryptococcus neoformans

Question 17

Most common cause of meningitis in renal postransplanted and cancer patients

Answer 17

Listeria monocytogenes

Question 18

Disease associated with mucor. Most important predisposing condition.

Answer 18

Rhinocerebral infection

Ketoacidotic diabetic, leukemia

Question 19

Diagnosis of meningitis by Cryptococcus

Answer 19

• capsular Ag ▶️ CSF
• India ink mount of CSF ▶️ budding yeast with capsular halos (misses 50%)
• cultures ▶️ urease (+) yeast

Question 20

Unique encapsulated fungal pathogen

Answer 20

Cryptococcus neoformans