Intro to Mycology Flashcards
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)
Arthroconidia
A sexual spore
Ascospore
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)
Blastoconidia
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)
Chlamydoconidia
Cell or cells born externally in various ways by fungi and which, when they mature, separate from the conidiophore
Conidia
Specialized structure of varying complexity which bears conidia
Conidiophore
Filaments, septate or aseptate, which make up the mycelium of fungi
Hyphae
Cell, usually more or less bottle-shaped, which forms conidia successively from its tip
Phialide
Chain of cells (usually in yeast) that form by budding; differ from true hyphae by having a constriction at the septation
Pseudohyphae
Mass of hyphae making up the colony of a fungus
Mycelia
Taxonomy of a human
Eukaryote
Taxonomy of bacteria
Prokaryote
Taxonomy of fungi
Eukaryote
What is the cell wall/membrane made up of in humans?
Cholesterol
What is the cell wall/membrane made up of in bacteria?
Peptidoglycan
What is the cell wall/membrane made up of in fungi?
Glucan and chitin (glucosamine)/ergosterol
Describe yeast (and YLF)
- 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
Describe molds
- Multicellular
- Microscopically seen as filaments (hyphae)
- Macroscopically look fuzzy or “wooly”
- Mass of mycelia (entertwined hyphae)
Nonpigmented or slightly pigmented hyphae
Hyaline
Having dark hyphae (brown or black)
Dematiaceous
Having crosswalls
Septate
Lacking crosswalls
Aseptate
Hyphae that grow w/in the surface of the medium (agar)
Vegetative
Hyphae w/ filaments that extend above the surface of the agar
Aerial
List the sexual forms of fungal reproduction
- Zygospores
- Ascospores
- Basidiospores
This form of fungal reproduction is rarely seen in tissue or studied in the lab?
Sexual
Fungus reproducing sexually
Teleomorph
What form of fungal reproduction is studied in the lab?
Asexual
List the asexual forms of fungal reproduction
- Blastoconidia
- Arthroconidia
- Chlamydoconidia
List the lab methods used in the identification of yeast and mold isolates
- Direct observation in patient tissue
- Lab culture/morphologic identification
- Direct Ag and Ab detection
List the stains that are used in direct observation of patient tissues
- 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
What is the purpose of the Gram stain in fungal identification?
- Most YLF stain GP
- Molds may vary according to pickup of stain
What is the purpose of the KOH method in fungal identification?
Breaks down keratin in nails, hair, and skin allowing a better view of the hyphae
What is the purpose of the Calcofluor white stain in fungal identification?
Fluorescent dye stains chitin
What is the purpose of the India ink in fungal identification?
Stains the capsule of Cryptococcus
What is the purpose of the Giemsa stain in fungal identification?
YLF stain blue
What is the purpose of the GMS stain in fungal identification?
ALL yeasts and hyphae are brown-black (not just dematiaceous)
What is the purpose of the PAS stain in fungal identification?
Fungi stain pink
What is the purpose of the LPCB stain in fungal identification?
- Only used on growing fungi, NEVER on patient specimens
- Morphology of hyphae, conidia, conidiophoer, and phialide stain blue
What is the best stain for examining hair, skin, and nails?
KOH
What is the best stain for examining mold cultures?
LPCB
What is the best stain for examining yeast cultures?
LPCB
List the fungal isolation media
- 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)
Incubation requirements for molds
22°-25°C (room temp)
Incubation requirements for yeast
37°C
How long are cultures held for?
4-6 weeks
Why are cases of fungal infections increasing?
- More immunocompromised patients (transplants, anti-cancer drugs)
- Invasive catheters (bladder, CNS, vascular)
- Use of broad-spectrum antibiotics
- Host has changed, not the fungi
How do people get mycoses?
- 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)
Which antifungal agent is responsible for renal toxicity?
Amphotericin B
Which “azole” antifungal agent is used only for yeast?
Fluconazole
