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

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93 Terms

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dematiaceous fungi list:

  • aureobasidium pullulans

  • Cladosporium spp.

  • Helminthosporium

  • bipolaris

  • cuvularia

  • Exserohilum

  • Alternaria

  • Ulocladium

  • stemphylium

  • Epicoccum

  • Nigrospora

  • Chaetomium (perithecia w/ ascospores)

  • Phoma (pycnidia)

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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

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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

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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

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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

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Aureobasidium pullulans basic info

  • Common contaminant; rare agent of phaeohypomycosis

  • moderately rapid growth

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

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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

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What can Aureobasidium pullulans be confused with?

  • Exophilia (wangiella) dermatitidis

  • Hortaea (phaeoannellomyces) werneckii

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

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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

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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

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Helminthosporium spp. basic info

  • common contaminant

  • rapid growth

  • dark gray to black colonies, black reverse

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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

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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

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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

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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)

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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

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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

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Exserohilum spp. basic info

  • causes phaeohyphomycosis

  • rapid growth

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

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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)

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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

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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

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Ulocladium spp. basic info

  • common contaminant; rarely causes phaeohyphomycosis

  • rapid growth

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

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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)

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Pithomyces spp. basic info

  • common contaminant

  • rapid growth

  • surface is cottony, brown to black ;dark reverse

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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

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Stemphylium spp. basic info

  • common contaminant

  • rapid growth

  • surface is browth to balck and cottony; black reverse

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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

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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

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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

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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

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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

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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

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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

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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

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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

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list of subcutaneous mycosis — A. fungi associated w/ mycetomas

  • Scedosporium spp. complex

  • Graphium spp.

  • Exophiala jeanselmei complex

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list of subcutaneous mycosis — B. fungi associated w/ Chromoblastomycosis and phaeohyphomycosis

  • fonsecaea pedrosoi

  • fonsecaea compacta

  • phialophora verrucosa

  • cladophialophora (cladosporium) carrionii

  • cladophialophora (xylohypha) bantiana

  • Exophiala (wangiella) dermatitidis

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list of cutaneous mycosis — dematiaceous fungi

  • hortae (phaeoannellomyces (exophiala)) werneckii

  • piedraia hortae

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Scedosporium spp. complex nomenclature

  • was considered an anamorph (asexual stage) of Pseudoallescheria spp., the telemorph (sexual) state

  • newer guidelines stipulate each fungus has only one name

  • Scedosporium is now the preferred name for the entire holomorph (sexual and asexual states) of the organism

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four spp. of Scedosporium complex that are clinically encountered:

  1. Scedosporium apiospermum — MOST common clinically; cleistothecia (indicative of sexual Pseudoallescheria apiospurmum) rarely develop in clinical cultures

  1. Scedosporium boydii — more likely to form cleistothecia; its telemorph is Pseudoallescheria boydii

  1. Scedosporium aurantiacum

  1. Scedosporium dehoogii

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pathogenicity of Scedosporium spp. complex

  • common cause of… mycetoma and phaeohyphomycosis

  • can cause fungus ball in CF pt… may disseminate

  • most often infects upper or lower extremities — may occur on any exposed parts of the body

  • Scedosporium spp. are the most common cause of eumycetoma in north america… can infect subcutaneous tissue, muscle, bones, lungs, sinuses, eyes, and CNS; also the most common cause of fatal lung/CNS infections complicating near-drowning accidents in immunocompromised pts

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Scedosporium spp. complex basic colony info

  • moderately rapid growth (<7 days)

  • spreading, white cottony aerial mycelium which turns gray/brown

  • reverse begins white then turns gray/black

  • spp. of the complex can be separated by reverse colony color, growth at 40C and 45C, and growth in cyclohexamide…

    • S. apiospermumi/boydii have variable yellow diffusible pigment, grow and 40C and grow in cycloheximide

    • S. aurantiacum cylindrical or slightly flask-shaped condidiogenous cells, reverse orangish colony, diffusible yellow pigment, growth at 40C AND 45C, and growth in cycloheximide

    • S. dehoogii has cylindrical or slightly flask-shaped condidiogenous cells, no pigment, does not grow at 40C OR 45C, but does growth in cyclohexamide

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Scedosporium spp. complex microscopic morphology

  • septate hyphae

  • short OR long conidiophores bearing unicellular, oval truncate (cut off at the base) conidia singly or in small groups

  • in the sexual state, large, brown cleistothecia can be formed, which release elliptical ascospores when ruptured

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Graphium spp. pathogenicity and basic info

  • common contaminant, can be another asexual synapomorph of Scedosporium spp.

  • moderately rapid rate of growth

  • colony morphology: gray, cottony surface, dark reverse

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Graphium spp. microscopic morphology

  • Septate hyphae

  • Long conidiophores that are cemented together, forming synemata

  • The apex of each synnema holds a cluster of oval, single-celled conidia

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Exophiala jeanselmei complex basic info and pathogenicity

  • pathogenicity: causes mycetoma (black grain) as well as phaeohyphomycosis

  • slow grower — <14 days at RT; may or may not grow at 37C

  • colony morphology — the surface is first dark and ‘skin like’ becoming velvety and gray; black reverse

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Exophiala jeanselmei complex microscopic morphology

  • young cultures have many yeast-like budding cells

  • older cultures will have septate hyphae w/ conidiophores bearing slender, tubular, sometimes branched annelids, which are characteristically tapered to a narrow, elongated tip

  • conidia are oval and clustered

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Fonsecaea pedrosoi basic info and pathogenicity

  • pathogenicity: MOST COMMON cause of chromoblastomycosis worldwide

  • slow grower — <14 days

  • colony morphology — surface is dark and velvety, usually flat but soon develops a convex cone-shaped protrusion in the center; black reverse

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Fonsecaea pedrosoi microscopic morphology

  • septate hyphae, usually branched

  • four types of conidial formation can be seen

    • fonsecaea type

    • cladosporium type

    • rhinocladiella type

    • phialophora type

  • characteristically, multiple types of conidiation (but not necessarily all) are seen in a single organism/colony

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Fonsecaea pedrosoi: conidial formation — fonsecaea type

septate, erect, and compactly sympodial conidiophores; swollen denticles bear single-celled oval primary conidia; denticles on the primary conidia support secondary single-celled conidia that may produce tertiary conidia, but long chains are not formed; conidia can form at fertile sites along the conidiophore, forming an asterisk-like appearance

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Fonsecaea pedrosoi: conidial formation — cladosporium type

erect conidiophores which produce shield-shaped conidia which in turn, produce chains of oval conidia having small dark hila

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Fonsecaea pedrosoi: conidial formation — rhindocladiella type

septate, erect, and sympodial conidiophores; swollen denticles bear oval conidia at the tip and sides of the conidiophores; chains of conidia are rare

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Fonsecaea pedrosoi: conidial formation — phialophora type

vase-shaped phialides w/ terminal cup-like collarettes; conidia accumulate at the apex of the phialides; this type of conidiation is very RARE

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Fonsecaea compacta basic info and pathogenicity

  • pathogenicity — causes chromoblastomycosis

  • very rarely encountered and considered as a mutant form of F. pedrosi

  • very slow grower <28 days

  • colony morphology — dark surface which is heaped and brittle; black reverse

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fonsecaea compacta microscopic morphology

  • septate and branched hyphae bearing predominantly fonsecaea type conidiophores, which produce short chains and masses of conidia in a compact arrangement

  • conidia have cask-like shape

  • other three types of conidiation may also be seen w/ this spp.

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Pleurostomophora (phialophora) richardsiae basic info and pathogenicity

  • pathogenicity — UNcommon agent of cystic subcutaneous phaeohyphomycosis

  • moderate rate of growth <10 day

  • colony morhpology — dark surface, brown diffusible pigment may develop w/ age; dark reverse

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Pleurostomophora (phialophora) richardsiae microscopic morphology

  • septate hyphae; similar to phialophora verrucosa

  • phialides are slightly flask-shaped w/ a characteristic flared, saucer-shaped collarette

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Cladophialophora (cladosporium) carrionii basic info and pathogenicity

  • causes chromoblastomycosis

  • slow grower <18 days

  • colony morphology — dark surface; black reverse

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Cladophialophora (cladosporium) carrionii microscopic morphology

  • septate hyphae

  • conidiophores produce long, branching chains of smooth, oval conidia w/ pale scars of attachment that are easily dispersed

  • in contrast to Cladosporium, ‘shield cells’ are usually NOT seen, does NOT grow in 15% NaCl, and is MDG assimilation positive

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Cladophialophora (Xylohypha) bantiana basic info and pathogenicity

  • pathogenicity — usually assoc. w/ disease of the CNS (cerebral phaeohyphomycosis); use extreme caution when handling

  • slow grower <15 days

  • colony morphology — dark surface; black reverse

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Cladophialophora (Xylohypha) bantiana microscopic morphology

  • septate hyphae

  • conidiophores resemble the hyphae

  • long, sparsely branched, wavy chains of smooth oval conidia which lack hila

  • no ‘shield cells’ seen, does not grow in 15% NaCl, and is MDG assimilation positive, max growth temp is 42-43C, whereas carrionii is 35-37

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temperature studies for: Cladosporium spp, Cladophialophora carrionii, and Cladophialophora bantiana

  • Cladosporium spp — growth at <37 C

  • Cladophialophora carrionii — growth up to 37 C

  • Cladophialophora bantiana — growth up to 42 C

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Exophiala (Wangiella) dermatitidis basic info and pathogenicity

  • pathogenicity — causes phaeohyphomycosis and seems to have a predilection for the CNS

  • rate of growth is slow (yeast-like within 10 days, filamentous within 25 days)

  • colony morphology — surface is at first black, moist, and yeast-like, then turns olive-gray with the development of aerial hyphae; dark reverse

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Exophiala (Wangiella) dermatitidis microscopic morphology

  • young cultures contain oval or round budding yeast-like cells

  • septate hyphae are eventually produced which bear flask-shaped or cylindrical phialides that lacka flared tipe

  • round or oval conidia are produced which accumulate at the apex of the phialides and dow to the hyphae

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‘black yeast’ differentiation

  • Exophiala jeanselmei spp. complex

    • casein decomposition negative

    • tyrosine decompositioin positive (78%)

    • NG in 15% NaCl

    • KNO assimilaiton positive

    • max growth </=37 C

  • Exophiala dermatitidis

    • casein decomposition negative

    • tyrosine decomposition positive (83%)

    • NG in 15% NaCl

    • KNO assimilation negative

    • max growth at 42 C

  • Hortaea werneckii

    • casein decomposition positive (78%)

    • tyrosine decomposition negative (only 22% pos)

    • Growth in 15% NaCl

    • KNO assimilation positive

    • max growth <37 C

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Lomentospora prolificans: Scedosproium prolificans (inflatum) — basic info and pathogenicity

  • causes localized and disseminated infections in a variety of sites; isolates are often resistant to antifungal agents and disseminated infections are commonly fatal

  • rapid grower <5 days

  • colony morphology — begins cottony or moist (yeast-like) becoming gray to black w/ age; the reverse is dark

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Lomentospora prolificans: Scedosproium prolificans (inflatum) — microscopic morphology

  • septate hyphae

  • similar to Scedosporium apiospermum

  • conidiogenous cells (annellides) have swollen base and elongated ‘neck’; conidia are dark, single-celled and ovoid w/ slightly narrowed, truncated (cut off) base

  • there is no known sexual state

  • no pigment, growth at 40C and variable growth at 45 C

  • NG in cyclohexamide, unlike Scedosporium spp.

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Hortae (phaeoannellomyces (exophiala)) werneckii — basic info and pathogenicity

  • pathogenicity — causes tinea nigra (brown or black ringworm)

  • slow grower <21 days

  • colony morphology — surface at first is lightly colored and yeast-like, turns dark w/ age; reverse is black

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Hortae (phaeoannellomyces (exophiala)) werneckii — microscopic morphology

  • young cultures have yeast-like cells, some of which have a central septum — usually annelids, round at one end, while tapered and elongated w/ striations at the other end where conidia are formed

  • closely septate hyphae eventually produced

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Piadraia hortae — basic info and pathogenicity

  • causes black piedra

  • slow grower <21 days

  • colony morphology — small, dark, compact colonies which may form a reddish-brown diffusible pigment; black reverse

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Piadraia hortae — microscopic morphology

  • closely septated hyphae w/ thick walls and variations in diameter

  • intercalary chlamydoconidia

  • asci may be produced which release single-celled, curved, tapering ascospores w/ whip like extensions

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overview of dermatophytes

  • among the most common infectious organisms of humans and are found worldwide

  • filamentous fungi that are able to digest and obtain nutrients from keratin; require keratin for growth (hair, skin, and rarely nails)

  • no invasion of living tissue, just colonization of the keratinized outermost layer of skin

  • only fungi that have developed a dependency on human/animal infection for survival; therefore, these fungi are the most common infectious agents of humans

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dermatophyte infecitons

  • tinea or ringworm

    • capitis — scalp/hair

    • barbae — bearded areas, face, and neck

    • corporis — body/trunk

    • pedis — athelet’s foot

    • cruis - groin

    • manum — hand

    • unguium — nail

  • onychomycosis — any infeciton of the nail, not necessarily by dermatophytes

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infection known as ______ is transmitted by direct contact w/ objects or materials contaminated w/ organism; the result of the host reaction to the enzymes released by the fungus during its digestive process

tinea/ringworm

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most infectious element of dermatophytes

arthroconidia

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media for dermatophytes =

dermatophyte testing media (DTM): contains chlortetracycline, gentamicin, and cycloheximide along w/ phenol red as a pH indicator; turns yellow to red in the presence of dermatophyte due to alkaline metabolites produced by the fungus

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hair perforation test

  • arthroconidia can be seen outside of the hairshaft (ectothrix) or inside the shaft (endothrix)

  • test is performed by suspending hair and test organism in a solution of distilled water w/ dilute yeast extract — hair should NOT be bleached, sprayed, or permed

  • the hair is incubated for up to four weeks and regularly examined microscopically

  • a positive reaction is indicated by wedge-shaped perforations caused by hyphae that penetrate the hairs perpendicularly

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flourescence w/ wood’s UV light

  • wood’s UV light at 365 nm can be helpful in detecting hairs infected w/ any of the fluorescent (bright greenish yellow) species of microsporum

    • M. audouinii

    • M. canis

    • M. ferrugineum

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dermatophyte — basic differentiation by conidial formation:

  • Microsporum spp. — macroconidia are numerous, thick-walled, and rough; microconidia are usually present

  • Trichophyton spp. — macroconidia are rare, thin-walled, and smooth; microconidia are numerous

  • Epidermophyton floccusum — macroconidia are numerous, thin- and thick- walled, and smooth; microconidia are absent

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Microsporum audouinii

  • formerly caused widespread epidemics of ringworm of the scalp in children

  • hyphae are separated w/ terminal chlamydoconidia pointed on the end

  • pectinate (comb like) hyphae are regularly seen

  • can be diagnosed by apple-green fluorescence of infected hair

  • seldomly produces conidia

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Microsporum canis

  • children tend to acquire infections of the scalp and skin from dogs/cats

  • macroconidia are spindle-shaped, rough, and thick-walled, taper to beak-like ends

  • microconidia are club-shaped and smooth-walled; form along the hyphae

  • colony is orange/yellow in color

  • contains >/= 6 septations

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Microsporum gypseum

  • colony is cinnamon in color

  • </= 6 septations

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Microsporum ferruguineum

  • primarily causes ringworm of the scalp (tinea capitis) in children

  • ‘bamboo’ hyphae

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Trichophyton overview

  • rare macroconidia, a thin wall, smooth surface, and multiseptate

  • elongated and pencil shaped

  • macrocondiia are NOT present in T. violaceum or T. schoeleinii

  • mciroconidia are usually very numerous except in T. violaceum or T. schoeleinii

  • testing for produciton of red pigment on cornmeal dextrose agar is useful to differentiate T. rubrum from T. mentagrophytes

  • hair, skin, nails — T. rubrum (most common dermatophyte) and T. mentagrophytes are quite common; hairs infected w/ T. schoenleinii also fluoresce (dull silvery to blue-green color)

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T. rubrum

  • presently most frequently isolated dermatophyte infecting humans worldwide

  • feet and nails are most common sites

  • macroconidia are pencil-like ; microconidia form directly on hyphae; arthroconidia form on both hyphae and macroconidia

  • urea is negative

  • hair preformation is negative (ectothrix)

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T. verrucosum

  • grows best at 37 C

  • forms hyphae w/ many intercalary chlamydoconidia (typically in chains) and some w/ antler-like branches; string-bean or rat tail macroconidia

  • requires thiamine and usually inositol for formation of macro/micro conidia; otherwise forms chlamydoconidia chains on SDA

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T. mentagrophytes

  • macroconidia are sometimes present but not always; they are cigar-shaped and thin-walled

  • invades all parts of the body surface, including hair and nails

  • common cause of athlete’s foot

  • urea is positive

  • hair perforation is positive (endothrix)

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T. schoenleinii

  • causes favus — severe chronic, scarring scalp infection

  • can lead to permanent hair loss

  • dull silver fluorescence

  • hyphae appear as antler-like branching structures (favic chandeliers) with swollen tips that resemble nail heads

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T. tonsurans

  • principal etiologic agent of scalp ringworm in the USA

  • also infects skin and nails

  • most common cause of outbreaks of tinea captis in children and is the main cause of endothrix (inside) hair infections

  • microconidia = teardrop or club-shaped but may elongate or enlarge to round balloon forms

  • intercalary and terminal chlamydoconida are common in older cultures

  • rare macroconidia — irregular form and bit thick-walled

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Epidermophyton floccosum overview

  • macroconidia are presnt, thick and thin walled, with smooth surface; 2-6 cells

  • with age, macroconidia are often transformed into chlamydoconidia

  • microconidia are absent

  • infects skin and nails, NEVER hair

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dermatophytes w/ round, tear-like or variously shaped microconidia, macroconidia w/ smooth thin walls may be present:

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dermatophytes forming only hyphal elements — no conidia usually seen on SDA:

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dermatophytes having macroconidia with thin or thick walls; usually no microconidia