General- Fungi and antifungals

Question 1

How do yeasts divide?

Answer 1

Budding

Question 2

Describe yeast colonies on solid agar

Answer 2

Bacteria-like

Question 3

How do molds grow?

Answer 3

Thread-like strands called hyphae

Question 4

How do mold colonies appear on agar?

Answer 4

Filamentous or mycelial

Question 5

Components of fungal cell wall

Answer 5

Manno-proteins, beta-glucan, and chitin

Question 6

Which type of hyphae are more durable to grinding and mechanical stress?

Answer 6

Septate

Question 7

What are conidia?

Answer 7

“Spores” in laymens terms (incorrect). Asexual reproducive structures. Found on structures called conidiophores.

Question 8

What is the Sabourad agar used for?

Answer 8

Fungal culture

Question 9

At what temperature are fungi cultured?

Answer 9

30 degrees C (close to ambient temperature; compare to bacteria cultured at 37 degrees C)

Question 10

What can India ink be used for?

Answer 10

Cryptococcus but NO LONGER RECOMMENDED

Question 11

How is a KOH prep performed?

Answer 11

10-20% KOH degrades host material (no cell wall). This exposes hyphae. Calcfluor white (binds chitin) is a fluorescent stain that may be used.

Question 12

What are pseudohyphae? How do they compare to true hyphae?

Answer 12

When yeast is budding, it elongates out; true hyphae is formed by apical extension with ‘pinching-off’ and formation of a cell wall

Question 13

What species can classically have hyphae and pseudohyphae?

Answer 13

Candida albicans

Question 14

What is silver stain used for?

Answer 14

Silver nitrate outlines fungi in black. May also stain some bacteria (e.g. Nocardia)

Question 15

What is mucicarmine generally used for?

Answer 15

Cryptococcus; stains mucin

Question 16

What is the best test to order for cryptococcus?

Answer 16

Cryptococcal antigen test (CSF or serum); should be backed up with fungal culture!!

Question 17

What fungi do not contain beta-D-glucan in their cell walls?

Answer 17

Cryptococcus, Mucorales, and the yeast phase of dermatitidis

Question 18

For which fungus does the (1,3)-beta-D-glucan (Fungitell) antigen assay have the greatest sensitivity and specificity?

Answer 18

Pneumocystis pneumonia

Question 19

For Aspergillus species, which test is superior: (1,3)-beta-D-glucan (Fungitell) antigen assay or serum galactomannan?

Answer 19

About the same

Question 20

What can cause false positives with the (1,3)-beta-D-glucan (Fungitell) antigen essay?

Answer 20

IVIG, hemodialysis membranes, surgical sponges

Question 21

What is galactomannan?

Answer 21

A cell wall polysaccharide produced by Aspergillus, Penicillium, Paecilomyces/Purpureocillium, and Histoplasma

Question 22

When is the galactomannan test generally used?

Answer 22

Suspected Aspergillus infection

Question 23

What is the antigen used in the Histoplasma antigen test?

Answer 23

Galactomannan, but optimized for Histoplasma rather than Aspergillus

Question 24

What are the two methodologies used in fungi antibody detection?

Answer 24

1) Complement fixation

2) Immunodiffusion

Question 25

What fungi can be detected by serological testing?

Answer 25

Histoplasma, Blastomyces, Coccioides (note- all endemic)

Question 26

Blastomyces dermatitidis- Labs

Answer 26

- Antigen test (urine, serum) - Culture - Antibody testing

Question 27

Blastomyces dermatitidis- Pathological findings

Answer 27

Broad-based budding yeast

Question 28

Blastomyces dermatitidis- Endemic locations

Answer 28

Eastern and central US

Question 29

Blastomyces dermatitidis- Presentation

Answer 29

Pulmonary infection that can disseminate to skin and bone; forms granulomatous nodules

Question 30

Cryptococcus neoformans- Pathogenesis

Answer 30

Spread by exposure to soil or pigeon droppings; hematogenous spread to meninges following inhalation

Question 31

Cryptococcus neoformans- Presentation

Answer 31

CNS infection (subacute to chronic) in AIDS patients

Question 32

Histoplasma capsulatum- Labs

Answer 32

- Antigen test - Culture - Antibody test

Question 33

Histoplasma capsulatum- Pathological findings

Answer 33

Yeast engulfed by macrophages

Question 34

Histoplasma capsulatum- Endemic locations

Answer 34

Mississippi and Ohio River valleys

Question 35

Histoplasma capsulatum- Presentation

Answer 35

Pulmonary or disseminated (or asymptomatic)

Question 36

Histoplasma capsulatum- Exposure history

Answer 36

Bird or bat droppings (i.e. caves)

Question 37

Cryptococcus neoformans- Labs

Answer 37

- CSF analysis (opening pressure) - Antigen (CSF or serum) - Molecular panels - Culture

Question 38

Coccioides immitis- Labs

Answer 38

- Antigen test - Culture - Antibody test

Question 39

Coccioides immitis- Pathological features

Answer 39

Spherule filled with endospores

Question 40

Coccioides immitis- Endemic locations

Answer 40

Southwestern US

Question 41

Coccioides immitis- Presentation

Answer 41

Pulmonary infection; usually self-limiting but can be fatal

Question 42

Sporothrix schenkii- Labs

Answer 42

Culture

Question 43

Sporothrix schenkii- Exposure history

Answer 43

Puncture by plant material (e.g. thorns)

Question 44

Sporothrix schenkii- Pathological features

Answer 44

Cigar-shaped yeast in the heat; characteristic 'rosettes' of conidia at ambient temperature

Question 45

Sporothrix schenkii- Presentation

Answer 45

Chronic infection, skin lesions, lymphangitis

Question 46

Candida- Labs

Answer 46

- Culture (may appear on routine/non-fungal cultures) - Molecular tests - (1,3)-beta-D-glucan antigen test

Question 47

Candida- Presentation

Answer 47

Cutaneous, mucocutaneous, invasive, and disseminated infections

Question 48

Candida- Pathological features

Answer 48

Presence of both hyphae and pseudohyphae

Question 49

Trichophyton- Labs

Answer 49

Culture

Question 50

Trichophyton- Pathogenesis

Answer 50

Host reaction to enzymes released by the fungus

Question 51

Trichophyton- Presentation

Answer 51

Tinea capitis, Tinea corporis, Tinea cruris, Tinea pedis, Tinea unghium

Question 52

Aspergillus fumigatus- Labs

Answer 52

- Galactomannan antigen test - (1,3)-beta-D-glucan antigen test - Culture - Molecular tests

Question 53

Where can Aspergillus fumigatus be found?

Answer 53

Environmental mold; decaying organic matter

Question 54

Who is at the greatest risk for infection with Aspergillus fumigatus?

Answer 54

Neutropenic patients

Question 55

Aspergillus fumigatus- Presentation

Answer 55

Pulmonary infection, including 'air-crescent' sign and nodules with ground-glass halo appearance. May lead to invasive infection, toxicosis, colonization, and allergy.

Question 56

Mucorales- Labs

Answer 56

- Culture | - Pathology

Question 57

Mucorales- Pathological features

Answer 57

Rapid growth ("lid-lifters") makes mucormycosis a medical emergency

Question 58

Mucorales- Presentation

Answer 58

Acute (often fatal) infection caused by inhalation of environmental mold or direct inoculation. Causes rhinocerebral, pulmonary, cutaneous, and GI effects (localized or disseminated).

Question 59

Fusarium- Labs

Answer 59

Culture

Question 60

Fusarium- Presentation

Answer 60

Mycotic eye infection, sinusitis, septic arthritis, nail infection, disseminated systemic infection