Intro to Mycology

Question 1

Conidia that result from the breaking up of a hypha into separate cells; look like float logs in a river (e.g., Coccidioides, Trichosporon, Geotrichum)

Answer 1

Arthroconidia

Question 2

A sexual spore

Answer 2

Ascospore

Question 3

Conidium which has been formed by budding (along hyphae, pseudohyphae or single cell yeast); daughter cells pinch off from mother cell (e.g., Candida, Cryptococcus)

Answer 3

Blastoconidia

Question 4

Thick-walled, intercalary or terminal cell containing stored food and able to function; form directly w/in or at the ends of hyphae and can fragment or break off to form new hyphae (e.g., Candida albicans-diagnostic, dermatophytes)

Answer 4

Chlamydoconidia

Question 5

Cell or cells born externally in various ways by fungi and which, when they mature, separate from the conidiophore

Answer 5

Conidia

Question 6

Specialized structure of varying complexity which bears conidia

Answer 6

Conidiophore

Question 7

Filaments, septate or aseptate, which make up the mycelium of fungi

Answer 7

Hyphae

Question 8

Cell, usually more or less bottle-shaped, which forms conidia successively from its tip

Answer 8

Phialide

Question 9

Chain of cells (usually in yeast) that form by budding; differ from true hyphae by having a constriction at the septation

Answer 9

Pseudohyphae

Question 10

Mass of hyphae making up the colony of a fungus

Answer 10

Mycelia

Question 11

Taxonomy of a human

Answer 11

Eukaryote

Question 12

Taxonomy of bacteria

Answer 12

Prokaryote

Question 13

Taxonomy of fungi

Answer 13

Eukaryote

Question 14

What is the cell wall/membrane made up of in humans?

Answer 14

Cholesterol

Question 15

What is the cell wall/membrane made up of in bacteria?

Answer 15

Peptidoglycan

Question 16

What is the cell wall/membrane made up of in fungi?

Answer 16

Glucan and chitin (glucosamine)/ergosterol

Question 17

Describe yeast (and YLF)

Answer 17

• Single-celled organism
• Round or oval that bud or pinch off
• Often elongate or form chains
• Most often stain GP
• Growth on agar resembles bacteria
• May be dry, pasty, or mucoid

Question 18

Describe molds

Answer 18

• Multicellular
• Microscopically seen as filaments (hyphae)
• Macroscopically look fuzzy or “wooly”
• Mass of mycelia (entertwined hyphae)

Question 19

Nonpigmented or slightly pigmented hyphae

Answer 19

Hyaline

Question 20

Having dark hyphae (brown or black)

Answer 20

Dematiaceous

Question 21

Having crosswalls

Answer 21

Septate

Question 22

Lacking crosswalls

Answer 22

Aseptate

Question 23

Hyphae that grow w/in the surface of the medium (agar)

Answer 23

Vegetative

Question 24

Hyphae w/ filaments that extend above the surface of the agar

Answer 24

Aerial

Question 25

List the sexual forms of fungal reproduction

Answer 25

- Zygospores - Ascospores - Basidiospores

Question 26

This form of fungal reproduction is rarely seen in tissue or studied in the lab?

Answer 26

Sexual

Question 27

Fungus reproducing sexually

Answer 27

Teleomorph

Question 28

What form of fungal reproduction is studied in the lab?

Answer 28

Asexual

Question 29

List the asexual forms of fungal reproduction

Answer 29

- Blastoconidia - Arthroconidia - Chlamydoconidia

Question 30

List the lab methods used in the identification of yeast and mold isolates

Answer 30

- Direct observation in patient tissue - Lab culture/morphologic identification - Direct Ag and Ab detection

Question 31

List the stains that are used in direct observation of patient tissues

Answer 31

- Gram stain - KOH - Calcufluor white - India ink - Giemsa stain - GMS (Gomori's Methenamine Silver) - PAS (Periodic Acid Schiff) - LPCB (lactophenol cotton blue) - H and E

Question 32

What is the purpose of the Gram stain in fungal identification?

Answer 32

- Most YLF stain GP | - Molds may vary according to pickup of stain

Question 33

What is the purpose of the KOH method in fungal identification?

Answer 33

Breaks down keratin in nails, hair, and skin allowing a better view of the hyphae

Question 34

What is the purpose of the Calcofluor white stain in fungal identification?

Answer 34

Fluorescent dye stains chitin

Question 35

What is the purpose of the India ink in fungal identification?

Answer 35

Stains the capsule of Cryptococcus

Question 36

What is the purpose of the Giemsa stain in fungal identification?

Answer 36

YLF stain blue

Question 37

What is the purpose of the GMS stain in fungal identification?

Answer 37

ALL yeasts and hyphae are brown-black (not just dematiaceous)

Question 38

What is the purpose of the PAS stain in fungal identification?

Answer 38

Fungi stain pink

Question 39

What is the purpose of the LPCB stain in fungal identification?

Answer 39

- Only used on growing fungi, NEVER on patient specimens | - Morphology of hyphae, conidia, conidiophoer, and phialide stain blue

Question 40

What is the best stain for examining hair, skin, and nails?

Answer 40

KOH

Question 41

What is the best stain for examining mold cultures?

Answer 41

LPCB

Question 42

What is the best stain for examining yeast cultures?

Answer 42

LPCB

Question 43

List the fungal isolation media

Answer 43

- Sabouraud Dextrose Agar (SDA or SAB) - SAB w/ antimicrobials (CSAB) → cyclohexamide inhibits bacteria and environmental fungi - Potato Dextrose Agar (PDA) or Potato Flake Agar (PFA) - BHI w/ blood (esp. yeast phase of dimorphics) - Mycosel (antibiotic and antifungal to inhibit saprobes)

Question 44

Incubation requirements for molds

Answer 44

22°-25°C (room temp)

Question 45

Incubation requirements for yeast

Answer 45

37°C

Question 46

How long are cultures held for?

Answer 46

4-6 weeks

Question 47

Why are cases of fungal infections increasing?

Answer 47

- More immunocompromised patients (transplants, anti-cancer drugs) - Invasive catheters (bladder, CNS, vascular) - Use of broad-spectrum antibiotics - Host has changed, not the fungi

Question 48

How do people get mycoses?

Answer 48

- Overgrowth of normal flora yeast (Candida) after catheters, chemo, or antibiotics - Inhalation of mold conidia - Trauma/implantation (Sporothrix) - Contact w/ plants (Sporothrix) and animals (dermatophytes)

Question 49

Which antifungal agent is responsible for renal toxicity?

Answer 49

Amphotericin B

Question 50

Which "azole" antifungal agent is used only for yeast?

Answer 50

Fluconazole