Mycology

Question 1

What is the purpose of the wood lamp?

Answer 1

Used to detect infection of hair, skin, or nails with certain dermatophytes. Hyphae and spores will fluoresce.

Question 2

What organisms can be identified with a wood lamp

Answer 2

Microsporum canis, Microsporum audouinii, Microsporum ferrugineum, Trichophyton schoenleinii, Malassezia furfur

Question 3

What are some general purpose stains?

Answer 3

10% KOH, 10% KOH w/ calcofluor, Lactophenol cotton blue

Question 4

What are some specialized stains?

Answer 4

Acid fast stain, India ink, Gomori Methenamine Silver Stain, Periodic Acid Schiff stain, Wright-Geimsa stain, Gram stain

Question 5

KOH prep

Answer 5

Potassium hydroxide dissolves cellular material allowing for the detection of hyphae or other morphological forms

Question 6

India Ink preparation

Answer 6

Used to detect the presence of C. neoformans in clinical specimens, particularly CSF. Capsular formation around yeast cell allows for differentiation of this encapsulated yeast from other yeast that may be present in the sample.

Question 7

Calcofluor White stain

Answer 7

Used with fluorescent microscopy. The CFW non-specifically binds to the chitin and cellulose in the fungal cell wall and fluoresces a bright green to blue.

Question 8

The Gram stain can be used to visualize which organisms?

Answer 8

Gram stain may be used when examining smears of Candida, Malassezia, and Sporothrix but should not be relied upon to demonstrate the yeast of the other dimorphic fungi.

Question 9

The H&E stain is used to visualize which organisms?

Answer 9

Aspergillus and Zygomycetes

Question 10

Non-selective media is used for?

Answer 10

Media that supports the growth of most bacterial and fungal contaminants as well as fungal pathogens.

Question 11

Examples of non-selective media?

Answer 11

BHI Agar with Blood, Cornmeal Agar, Sabouraud Dextrose Agar (SAB), SABHI agar (Emmons’ modification contains
2% glucose and is slightly acidic [pH 6.5]), Potato Dextrose Agar (PDA)

Question 12

Selective fungal media is used for?

Answer 12

Media contains antibiotics and / or inhibitory agents to prevent the overgrowth of bacterial and fungal contaminants.

Question 13

Anthropophilic organisms

Answer 13

Dermatophytes that are restricted to human hosts and produce a mild,chronic inflammation.

Question 14

Zoophilic

Answer 14

Organisms that are found primarily in animals and cause marked inflammatory reactions in humans who have contact with infected cats, dogs, cattle, horses, birds, or other animals.

Question 15

Geophilic

Answer 15

Recovered from the soil and only occasionally infect humans and animals. They cause a marked inflammatory reaction, which limits the spread of the infection and may lead to a spontaneous cure but may also leave scars

Question 16

What is the most common dermatophyte that causes anthropophilic infections? Which infections

Answer 16

Trichophyton rubrum. Causes: tinea pedis/tinea cruris, tinea corporis, tinea capitis

Question 17

Organisms that cause onychomycosis:

Answer 17

T. rubrum (most common), S. dimidiatum, Acremonium, Fusarium (cause superficial white onychomycosis)

Question 18

Grey patch capitis

Answer 18

Hyphae fragment into arthroconidia (spores) outside the hair shaft. This eventually ends in cuticle destruction. There are inflammatory and non-inflammatory varieties (Ectothrix infection)

Question 19

Black dot capitis

Answer 19

Arthroconidia (spores) occur within the hair shaft and cuticle destruction does not occur. There are also non-inflammatory and inflammatory varieties (Endothrix infection)

Question 20

Favus/Inflammatory diffuse, pustular kerion

Answer 20

Scattered painful pruritic pustular folliculitis. Boggy nodules studded with broken hairs and purulent sticky material (“kerion”) appear. Scarring alopecia develops

Question 21

Tinea favosa

Answer 21

Caused by M. gypseum, Trichophyton schoenleinii.

The occurrence of dense masses of mycelium, and epithelial cells forming yellowish cup-shaped crusts called scutula.