intro to mycology

vegetative

food-absorbing hyphae under surface of agar

mold

yeast/mold have hyphae

aerial

hyphae that extend above agar surface supporting conidia

aseptate

no cross walls

septate

have cross walls

terminal

chlamydospores at hyphal tip

intercalary

chlamydospores within hyphae

sessile

chlamydospores arising on side of hyphae

hyaline

describes colorless/white pigmentation

dematiaceous

describes brown/black pigmentation

37

yeast/tissue phase growth temp

dimorphism

fungi grow as yeast at one temp and as mold in another

25

mold phase growth temp

sporangiospores

asexual spores of zygomycetes

-form within sac like struct

sporangia

structure that holds asexual spores of zygomycetes

conidia

arise by budding off specialized hyphae (not in sac)

conidiophores

specialized hyphal structures that produce conidia

metulae

terminal branches of conidiophores in Penicillium spp

asexual

imperfect reproduction

-structures: phialoconidia, annelloconidia, arthroconidia, blastoconidia, macro/microconidia, sporangia

sexual (telomorph)

perfect reproduction

-requires joining of two compatible nuclei followed by meiosis

-two forms: asexual (anamorph) and synamorph

anamorph

asexual form of telomorph

synamorph

telomorph producing more than one anamorph

ascospores

sexual spores

cleistothecium

round structure that holds ascospores and ascus

-class Ascomycota

-pac man when open

Zygomycota (zygomycetes)

-soil molds

-asexual stage seen most freq

-sporangiospores on aseptate hyphae

Ascomycota (ascomycetes)

-ascospores and ascus

-Pseudoallescheria boydii

Basidiomycota (basidiomycetes)

-produce basidiospores sexually

-sexual form of Cryptococcus neoformans

Deuteromycetes

-Fungi imperfecti

-identified by asexual reproductive structures

-majority of pathogenic fungi

superficial

mycoses affecting outermost layer of skin or hair

-tinea versicolor

cutaneous

mycoses affecting keratinized tissue

-Dermatophyte infections

-itchy, scaly skin, brittle hair, discolored nail

subcutaneous

mycosis of deeper skin layers: muscle, connective tissue, bone

-chromoblastomycosis

-phaeohyphomycosis

-eumycotic mycetoma

systemic

disseminated mycosis: internal organs or deep tissues

-dimorphics

opportunistic

mycoses infections by 

-aseptate and hyaline fungi

-septate and hyaline saprophytes

-septate and dematiaceous saprophytes

rugose

-topography morphology

-deep furrows irregularly radiating from center of culture

umbonate

-topography morphology

-button-like central elevation

verrucose

-topography morphology

-wrinkled, convoluted surface with no defined center

2

BSL for working with fungi

hood

bench/hood is best place to work with fungi

no

yes/no

negative pressure rooms are required to work with fungi

saline wet prep

direct examination of yeast specimen

lactophenol cotton blue (LPCB)

-primary stain

-molds

phenol

LPCB component that kills orgs

cotton blue

LPCB component that stains chitin of cell walls

lactic acid

LPCB component that preserves fungal struct

calcofluor white

-fluorescent dye

-blue

-binds to polysacch in chitin

KOH

clearing agent for fluorescence examination

-green

-breaks down keratin and skin layers

india ink

-negative stain

-observe yeast capsule

-usually CSF cultures

Periodic acid Schiff (PAS)

histology stain

-fungal elem light pink or green against background

Gomori methenamine silver (GMS)

histology stain

-fungal elem black against green background

gentamicin, chloramphenicol, cyclohexamide

antibiotics in inhibitory media

gentamicin

antibiotic inhibits bacteria

chloramphenicol

antibiotic inhibits fungus-like bacteria and yeast phases of dimorphic fungi

cycloheximide

antibiotic inhibits fungus-like bact, many yeasts and fungal opportunists (sapros)

sabouraud dextrose agar (SDA)

-general media

-acid pH with high dextrose to inhibit bact

-yeast isolation

inhibitory mold agar (IMA)

-general media

-nutrient rich

-contains antibiotics to inhibit bact

-fungus selective

BHI

-general media

-nutrient rich

-contains blood, peptone, dextrose, maybe antibiotics

-nonselective, but good for dimorphics

cycloheximide

-general media

-inhibits sapro fungi

-promotes growth of slow-growing, pathogenic fungi

CHROMagar

-general media

-chloramphenicol

-selective for yeast

-color to identify yeast species

mycosel

-general media

-chloramphenicol and cycloheximide

-selective for dermatophytes (skin, hair, nail samples)

potato dextrose agar (PDA)

-special media

-stresses mold to get sporulation 

-repro struct and pigment

rice agar with Tween 80

special media for yeast structure identification

cornmeal

special media for repro/struct for mold and yeast identification

-chlamydospores, blastoconidia, arthroconidia, pseudohyphae

bird seed agar

-special media

-phenol oxidase activity in C. neoformans

-black: pos

aerobic (O2)

ambient air for incubation

4-6 wks

time held for no growth

one month

Histoplasma hold time for no growth

2

read plates x times a week

shrink seal

how to keep fungi from drying out during incubation

scotch tape

procedure used to visualize mold with LPCB

true

true/pseudo germ tube lacks constriction around base

pseudo

true/pseudo germ tube has constriction around base

42

temp study for Candida

-C. albicans grows

-C. dublinensis does not

trehalose

-carbohydrate assimilation and fermentation test

-pos identifies C. glabrata

5 day urease

test pos for Trichophyton mentagraphytes, Cryptococcus, and Rhodotorula

-neg for Trichophyton rubrum and Candida spp.

-pink: pos

hair perforation

-penetration: pos

-Trichophyton mentargraphytes pos

-Trichophyton rubrum neg (surface erosion only)

Cryptococcus

testing involves latex agglutination for antigen detection

Aspergillus

testing involves exoantigen immunodiffusion or temperature studies

qualitative (colorimetric)

Fungitell STAT

-detection of (1,3)-B-D-glucan

-immunocompromised patients with risk of disseminated fungal infections

-Candida, Apergillus, Pneumocystis

fluorescence (CO2)

BD BACTEC FX40

-automated blood culture system

-detection for mycobacteria, yeast, fungi using Myco/F lytic bottle

macrolides

therapy for Aspergillus, Candida, Cryptococcus

-Amphotericin B

azoles

therapy for Candida, C. neoformans, Coccidioides, Histoplasma, Paracoccidioides, Blastomyces

-ketoconazole, fluconazole, itraconazole, posaconazole, voriconazole

echinocandins

therapy for Candida and Aspergillus

-caspofungin

allylamines

therapy for fungal nail inf or onyochomycosis, athletes foot

-terbinafine (Lamisil)

Flucytosine

antifungal therapy for Candida, C. neoformans, Aspergillus

Griseofulvin

antifungal therapy for dermatophytes: Microsporum, Epidermophyton, Trichophyton

Macrolides, Azoles, Echinocandins, Allylamines

four classes of mycoses therapy