SOLO 3 -- dematiaceous fungi, subcutaneous/cutaneous mycoses, dermatophytes

dematiaceous fungi list:

• aureobasidium pullulans

• Cladosporium spp.

• Helminthosporium

• bipolaris

• cuvularia

• Exserohilum

• Alternaria

• Ulocladium

• stemphylium

• Epicoccum

• Nigrospora

• Chaetomium (perithecia w/ ascospores)

• Phoma (pycnidia)

dematiaceous fungi overview:

• dark colonies — melanin pigment in cell walls

• diseases are classified according to presentation and appearance of organism in tissue:

  • chromoblastomycosis

  • phaeohyphomycosis

  • mycetoma

chromoblastomycosis

• fungi in tissues are seen as sclortic bodies or “copper pennies.”

• chronic infection, which causes warty nodules, tumor-like masses, or cauliflower-like lesions containing sclerotic bodies

• the lesions usually develop in subcutaneous tissue of the lower extremeities but are sometimes on other exposed areas, such as hands, head, or trunk

phaeohypomycosis

• fungi appear as dark, yeast-like cells, pseudohypha-like elements, variously shaped hyphae, or any combination of these forms

• can be cutaneous, subcutaneous, or systemic

mycetoma

• characterized by swollen, tumor-like lesions containing granular pus through draining sinuses

• very few of the meatiaceous fungi are etiologic agents of this disease

• usually in hands or feet

Aureobasidium pullulans basic info

• Common contaminant; rare agent of phaeohypomycosis

• moderately rapid growth

• white at first, matures to black, shiny, and leathery; black reverse

Aureobasidium pullulans microscopic morphology

• young colonies are typically yeast-like

• two types of hyphae:

  • hyaline, delicate: thin walled, producing conidia directly from the walls at certain fertile points

  • thick walled, dark, closely seprated: with some cells forming short tubes which produce hyaline and oval onidia

What can Aureobasidium pullulans be confused with?

• Exophilia (wangiella) dermatitidis

• Hortaea (phaeoannellomyces) werneckii

***review rate of growth and microscopic morphology for each***

Cladosporium basic info

• common contaminant; must be differentiated from cladophialophora spp.

  • Cladophialophora carrionii causes chromoblastomycosis (Australia, Venezuela, South Africa)

  • Cladophialophora bantiana causes cerebral phaeohyphomycosis

• moderately rapid growth

• greenish brown to black colonies, becoming heaped or folded; black reverse

Cladosporium microscopic morphology

• dark septate hyphae

• branched conidiophores, which may produce two or more conidial chains

• conidia are oval and form branching tree-like chains, which are easily dislodged, revealing dark spots (hila -scars of attachment)

• “shield cells” are also present

Helminthosporium spp. basic info

• common contaminant

• rapid growth

• dark gray to black colonies, black reverse

Helminthosporium spp. microscopic morphology

• septate hyphae

• conidiophores are brown and determinate (do not elongate at the point of conidium formation)

• condidia characteristics

  • form along sides of conidiophores

  • frequently in whorls

  • large

  • club-shaped w/ broader end toward the conidiophore

  • usually contains six or more cells

Bipolaris spp. basic info

• common contaminant, but occasionally can infect the eye, bones, aorta, sinuses, lung, brain, and skin

• rapid growth

• graish brown colonies at first, becomes black w/ matted center and raised gray periphery; black reverse

Bipolaris spp. microscopic morphology

• septate hyphae

• conidiophores elongate and bend at the point where each conidioum is formed (sympodial geniculate growth)

• conidia are thick-walled, oblong, or cylindrical, have 3-5 septations, and a slightly protruding hilum

Bipolaris spp. confirmation

• germ tube test must be performed

• differentiates Bipolaris spp. from Drechslera spp.

  • bipolaris spp. germinate at the ends (poles) of the conidia

  • Drechslera spp. germinate on the sides of conidia (perpendicular to axis)

Curvularia spp. basic info

• contaminant and opportunistic pathogen; can cause phaeohyphomycosis

• rapid growth

• colony surface is dark olive green to brown or black w/ pinkish gray surface; dark reverse

Curvularia spp. microscopic morphology

• septate hyphae

• simple or branched conidiophores that are geniculate

• large conidia, which usually contain four cells, appear curved due to the swelling of the central cell

• The central cell also tends to be darker than the end cells

Exserohilum spp. basic info

• causes phaeohyphomycosis

• rapid growth

• surface is dark gray or black and cottony; black reverse

Exserohilum spp. microscopic morphology

• septate hyphae

• elongated, geniculate conidiophores

• conidia are long, fusiform, and usually has 7-11 septa

• hilum is dark, conspicuous, and usually square

• germ tubes are produced along the axis of the conidium

• distinctive dark septum at each end of cell (basal and distal septa)

Alternaria spp. basic info

• common contaminant but sometimes assoc w/ phaeohyphomycosis

• rapid growth

• surface is graish white and wooly, becoming greenish black or brown; reverse is black

Alternaria spp. microscopic morphology

• septate hyphae

• septate conidiophores w/ zig-zag appearance

• large conidia w/ transverse longitudinal septations (muriform)

• conidia form singly or in chains, and take club-like shape

Ulocladium spp. basic info

• common contaminant; rarely causes phaeohyphomycosis

• rapid growth

• surface is cottony, dark brown to black; black reverse

Ulocladium spp. microscopic morphology

• septate hyphae

• simple or branched conidiophores that are bent at the point of conidial produciton

• conidia can be smooth/rough, round to oval, w/ transverse and logitudinal septations (muriform)

Pithomyces spp. basic info

• common contaminant

• rapid growth

• surface is cottony, brown to black ;dark reverse

Pithymyces spp. microscopic morphology

• septate hyphae

• peglik conidiophores (much shorter and simpler than Ulocladium)

• conidia are oval, yellow to brown, and rough w/ transverse and longitudinal septations

Stemphylium spp. basic info

• common contaminant

• rapid growth

• surface is browth to balck and cottony; black reverse

Stemphylium spp. microscopic morphology

• septate hyphae

• simple or branched conidiophores w/ swollen terminus bearing individual conidia

• The condia are smooth/rough, round or oval, and have transverse and longitudinal septations, sometimes marked w/constriction at the central septum

Epicoccum spp. basic info

• common contaminant

• moderatley rapid growth

• cottony, yellow to orange becoming dark w/ age colonies; reverse is sometimes red w/ diffusible pigment that may turn the agar yellow, orange, red, or brown

Epicoccum spp. microscopic morphology

• conidiophores form in clusters on hyphae by repeated branching to form a dense mass from which conidia arise

• Young conidia are smooth/round or pear-shaped; mature conidia are round w/ transverse and longitudinal septations and are often rough/warty

• characteristically, all stages of condia will present simultaneously in clusters

Nigrospora spp. basic info

• common contaminant

• rapid growth

• wooly, surface is white turning gray with age; black areas of conidiation apepar as it ages; reverse is black

Nigrospora spp. microscopic appearance

• septate hyphae

• short, swollen conidiophores which taper at the poitn of conidia formation

• conidia are large and densely black, almost round, and slightly flattened

Chaetomium spp. basic info

• common contaminant; occassionally causes phaeohyphomycosis

• rapid growth

• surface is cottony, usually white but comes gray to grayish olive w/ age; reverse is usually orange-tan tinted w/ red but may be dark

Chaetomium spp. microscopic appearance

• septate hyphae

• large, round, oval, or flask-shaped perithecia that have wavy and/or straight filamentous appendages (setae)

• asci contain four to egith oval or lemon shaped ascospores, and usually dissolves after release from the ostiole of the perithecium

Phoma spp. basic info

• common contaminant that can cause phaeohyphomycosis

• rapid growth

• surface is powdery or velvety

• graish-brown; reverse is black; some spp. have a reddish or brown diffusible pigment

Phoma spp. microscopic morphology

• septate hyphae

• large pycnidia (asexual fruiting bodies), which are dark and round or flask-shaped and have ostioles

• conidia (formed on conidiophores inside the pynicida) are oval, single-celled, and hyaline