intro to mycology + lab procedures for fungal cultures

favic chandeliers

resemble deer antlers

nodular organs

knots of twisted hyphae

pectinate

comb-shaped

racquet hyphae

resembles tennis racquets placed end to end

spiral hyphae

may be flat or corkscrew shaped

sexual reproduction

produce fruiting bodies (ascomata/ascocarp). ascomata → asci → ascospores. ex: chaetomium spp, pseudallescheria boydii

perithecium

type of ascomata (fruiting body). disperses spores through an opening called an ostiole.

cleistothecium

type of ascomata (fruiting body). lacks specialized opening. splits under pressure, releasing spores

asexual spores

produced from cytoplasmic cleavage. ex: sporangiospores

conidiophore

specialized hypha upon which the conidia develop. can refer to a conidiogenous cell or specialized structure supporting a conidiogenous cell or cells

conidiogenous cells

specialized cells that produce conidia. ex: annellides & phialides

conidium (conidia)

unicellular or multicellular fungal element specialized to detach from the mycelium & disseminate

blastoconidia

seen in molds or yeasts. molds: bud at apex or side of conidiophore or from another conidium. yeasts (candida): elongate to form pseudohyphae

phialoconidia

bottle shaped conidiogenous cells. apices produce conidia in masses or in chains. some apices have collarettes

anelloconidia

produce conidia in masses or in chains. deep staining truncated bases. series of annular rings at apex (not easily seen with light microscopy.

arthroconidia

arise from transformation of a series of cells long length of hypha. contiguous is simple. intercalated have separating cells (alternate)

chlamydoconidia

environmentally resistant resting cells that are formed from pre-existing cells within a hypha. inflated round cells with thick walls. seen in older cultures. ID marker for T. verrucosum

aleuroconidia

terminally or laterally located. truncated bases w/ small annular frills. macroconidia: larger, produced by same fungus, often multicellular. microconidia: smaller, produced by same fungus, unicellular

glabrous

smooth surface because they do not produce aerial mycelium. ex: yeasts

rugose

deep furrows irregularly radiating from center of culture

umbronate

button-like central elevation. may also have rugose furrows around elevation

verrucose

wrinkled & convoluted

dermatophytosis

diseases caused by microsporum, epidermophyton, trichophyton

common organisms on skin

dermatophytes, candida spp, malassezia spp, sporothrix schenkii

common organisms on hair

dermatophytes, candida spp, trichosporon spp, piedraia hortae

common organisms on nails

dermatophytes

common pathogens in respiratory

aerobic actinomycetes, aspergillus spp. dimorphic fungi: histoplasma capsulatum, blastomyces dermatitidis, coccidioides immitis

common organisms in blood

candida spp, cryptococcus neoformans, malassezia spp, histoplasma capsulatum

common organisms in sterile body fluids

histoplasma capsulatum, cryptococcus spp

common organisms in tissue specimens

yeast & filamentous fungi. aerobic actinomycetes

KOH prep

dissolves keratin & cellular debris while fungal elements remain visible

calcofluor white stain

binds fungal cell wall components (chitin). highly sensitive. fungi fluoresce bright white or blue-white

india ink stain

detection of encapsulated yeasts. classically used for cryptococcus neoformans from CSF. clear halo surrounding yeast cell

gram stain

yeasts stain gram-positive. demonstrates budding yeast & pseudohyphae

giemsa stain

blood & bone marrow specimens. used to look for histoplasma capsulatum, an intracellular organism that appears as small oval to pear-shaped yeast-like cells

modified acid-fast stain

differentiate acid-fast nocardia (bacteria) from other true fungal elements

mucicarmine stain

highlights cryptococcal capsule. capsule stains red

sabouraud’s dextrose agar (SAB or SDA)

primary isolation medium. grows non-patho & patho fungi. acidic pH inhibits bacteria. H. capsulatum & nocardia will not grow.

sabouraud’s dextrose with brain heart infusion agar (SABHI)

primary isolation medium superior to SAB. enriched for recovery of yeasts. chloramphenicol & gentamicin can be added to inhibit bacteria. cycloheximide can be added to inhibit rapidly growing fungi

mycosel agar

isolation of dermatophytes. chloramphenicol to inhibit bacteria. cycloheximide to inhibit saprophytic fungi & some yeasts

brain heart infusion slant (BHI)

more enriched than SAB. used in recovery of H. capsulatum

BHI with chloramphenicol & gentamicin

used for selective isolation of fungi from specimens heavily contaminated with bacteria

potato-dextrose agar & corn-meal agar

used in slide cultures. induces spore formation, aids in ID

caffeic acid agar (bird seed agar aka niger seed agar)

selective isolation & differentiation of cryptococcus neoformans & cryptococcus gatti. C. neoformans will produce melanin → black colonies. protect media from light

temperature fungal growth requirements

25-30C for most molds, some dimorphics prefer 37C.

35-37C for yeast

teased preparation

advantage: performed imediately after maturation of fungal colony

disadvantage: teasing disturbs hyphae & conidia, can make discerning morph difficult

slide culture techniques

advantage: undisturbed microscopic morphology

disadvantage: technical expertise, must wait for fungus to grow before examining

transpararent tape preparation

performed immediately after maturation of fungal colony

lactophenol cotton blue (LPCB)

lactic acid: clearing agent, helps preserve fungal structures

phenol: kills fungus, making it safe to remove slide from BSC

glycerol: slightly viscous, prevents drying of prepared slide

cotton blue: aniline dye, adds color to fungal prep, enhances & contrasts structures