(dematiaceous fungi) mycology quiz 2 - micro II (cls 542)

dematiaceous fungi

• Brown to black pigment in the cell walls

• Found more in tropical regions or where people go barefoot

• Cause the following diseases:

  • Chromoblastomycosis

  • Mycetoma

  • Phaeohyphomycosis

  • Sporotrichosis

evidence for an organism being a pathogen instead of a contaminate

• Isolation of organism from multiple cultures from the same location

• Isolation of organism on more than one plate or tube of media

• Isolation of organism from a normally sterile site

• Ability of the organism to grow at 37 C

specimen types for subcutaneous fungi infections

• Aspirates, biopsy material, scrapings, surgical tissue specimens

• Protect from dehydration (except for skin scrapings)

• Avoid the use of cotton swabs

  • Contains fatty acids

  • Cotton fibers look like hyphae

  • Difficult to get the material out of the cotton

(dematiaceous; subcutaneous) chromoblastomycosis

• Acquired via traumatic inoculation

• Papule develops

  • turns into a warty ‘cauliflower’ lesion

  • Hyphae near the surface

• Muriform cells in the deeper tissues

  • Muriform cells, medlar bodies, sclerotic bodies, or “copper pennies”, is diagnostic for the disease

causative agents for chromoblastomycosis 

• Fonsecaeae pedrosoi

• Cladophialophora carrionii

• Phialophora verrucosa

• Rhinocladiella aquaspersa

• Exophiala jeanselmei

• Exophiala spinifera

diagnosis of chromoblastomycosis

• Skin scraping 10% KOH prep

• Brown pigmented, planate-dividing rounded sclerotic bodies (aka copper pennis or muriform cells)

• tissue biopsy

(chromoblastomycosis) phialophora verrucosa

• Slow growing (7-12 days)

• Suede-like texture

• Colonies become embedded in the agar

• Reverse is black

phialide vs annelide 

• Phialide: flared collarette

• Annellide: tapered collarette with growth rings; need 100x to visualize

(chromoblastomycosis) fonsecaea pedrosi

• A mould of many hats

• 4 sporulation patterns (1st pic)

  • a. Fonsecaea type ; b. Cladosporium type

  • c. Rhinocladiella type ; d. Philophora type

• Fonsecaea type:

  • Denticle--short stalk-like structure from which conidia arise

    • Hard to see; Can be thin or swollen

colony morphology of fonsecaea pedrosi 

• Slow growing

• Silvery, velvety surface that turns black

• Colonies slightly embed into media

• Reverse in black

(chromoblastomycosis) cladophialophora carrionii

• Slow growing

  • Mature in 18 days

• Velvety, dull dark surface

• Reverse is black

• Cladosporium type sporulation

• somewhat poiny conidia

mycetoma

• Chronic granulomatous infection

• Primarily seen on the lower extremities

• Swollen, purplish discoloration, tumor like deformities of the subcutaneous tissues

• Multiple draining sinus tracts w/ pus and ‘sulfur’ granules

• Painless Infection

• Progresses to a bone infection and usually requires amputation

epidemiology of mycetoma

• Found in tropical and hot temperate zones of the world

• Not endemic in the USA

  • Those at risk:

    • Farmers / Field Workers

    • Sugarcane Workers

    • Fishermen

types of mycetoma (2)

• Eumycotic– caused by dematiaceous fungi

• Actinomycotic– caused by bacteria

• Both are acquired by traumatic implantation

• Everything except the etiological agent is the same

 

(mycetoma) exophiala jeanselmei complex colony morphology 

• Matures in 14 days

• Grows slower or not at all at 37 C

• Starts off as moist and skin like

• Gradually develops velvety, short, mycelia

• Reverse is black

• colony can become elevated

(mycetoma) exophiala jeanselmei complex microscopic morphology 

• Slender annellides, sometimes branched

• Conidia clustered at the end of the tapered annellide

• Oval/elongated conidia

(mycetoma) scedosporium

• Formerly Pseudallescheria boydii

• Mature in 7 days

• White, spready cottony, aerial mycelium turns gray to dark brown as it ages

• Reverse – white changing to black

• Asexual state grows in presence of Cyclohexamide

morphology of asexual stage of scedosporium

• Septate hyphae

• Conidiophores produce single conidia

• Conidia appear cut off at base

  • Flattened end/truncate

sexual stage of scedosporium

• Cleistothecia

  • Large sack

  • contain asci that contain ascospores when ruptured

• development inhibited by cycloheximide

phaeohyphomycosis

• Can be superficial, cutaneous, subcutaneous or invasive/systemic forms

  • May cause keratitis

• Yeast-like cells and/or hyphae are seen in the tissues

  • No ‘unique’ structures seen

causative agents of phaeohyphomycosis (6)

•  rapidly growing moulds--mature in about 3-5 days

  • Alternaria

  • Aureobasidium

  • Bipolaris

  • Cladosporium

  • Curvularia

  • Hortaea

(phaeohyphomycosis) alternaria sp colony morphology

• Wool surface with short aerial mycelia

• Greyish-greenish-sometimes black

• Light border

• Reverse is black

• Mature in 5 days

sporulation pattern of alternaria sp

• racket-shaped conidia are the characteristics identification feature, regardless of the arrangement

  • AKA murifrom cells

(phaeohyphomycosis) aureobasidium pullulans colony morphology

• Starts as white, moist, creamy colonies

• Develops brown/black shiny areas

• Matures in 3-5 days

• Reverse is black once mature

hyphae of aureobasidium pullulans (2)

has 2 types:

• Chains of darkly pigmented arthroconidia that break apart into arthrospores

• Hyaline hyphae that produce oval hyaline conidia on denticles

(phaeohyphomycosis) biopularis sp

• Gray/brown turning to black

• Reverse is black

• Matures in 5 days

• genticulate/zig-zag conidiophore + dark conidia

germ tubes of biopularis sp (pic)

(phaeohyphomycosis) curvularia sp macro + microscopic morphology

• Black wooly surface

• Matures in 5 days

• Reverse is black

• Dark multi-celled conidia arise from pores on the Geniculate conidiophore

• One of the central cells of the conidia grows faster than the others

  • That’s why it curves

(phaeohyphomycosis) hortaea werneckii 

• Formerly known as Wangiella werneckii

• Slow grower—matures in 21 days

• Moist, shiny, yeast-like at first

• Starts brownish then becomes a dull olive black

• Reverse is dark

• 2-celled, brown, yeast-like conidia w darkly pigmented septa

(phaeohyphomycosis) cladosporium sp colony morph + microscopic pic

• Saprophytic contaminant, but still dematiaceous

• Matures in 7 days

• Greenish brown to black, becomes heaped, folded with a velvety texture

• Very similar to Cladophilophora, except conidia are NOT pointy