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

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

• Scedosporium spp. complex

• Graphium spp.

• Exophiala jeanselmei complex

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

list of cutaneous mycosis — dematiaceous fungi

• hortae (phaeoannellomyces (exophiala)) werneckii

• piedraia hortae

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

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

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

3. Scedosporium aurantiacum

4. Scedosporium dehoogii

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

Pleurostomophora (phialophora) richardsiae microscopic morphology

• septate hyphae; similar to phialophora verrucosa

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

Cladophialophora (cladosporium) carrionii basic info and pathogenicity

• causes chromoblastomycosis

• slow grower <18 days

• colony morphology — dark surface; black reverse

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

  

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

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

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

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

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

‘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

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

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.

  

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

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

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

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

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

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

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

most infectious element of dermatophytes

arthroconidia

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

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

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

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

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

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

Microsporum gypseum

• colony is cinnamon in color

• </= 6 septations

Microsporum ferruguineum

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

• ‘bamboo’ hyphae

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)

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)

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

  

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)

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

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

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

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

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

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