Systemic Mycosis Week 12

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Coccidioides immitis infection

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Coccidioidomycosis

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Colony Morphology
– Variable: often described as a “white fuzzy”
– No yeast phase, forms a spherule in tissue

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Coccidioides immitis

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Microscopic:
– Coarse Septate branched hyphae
– Thick walled barrel shaped arthroconidia (may take two weeks to develop)
– Arthroconidia alternate in the hyphae with empty cells that break away
– Spherules are large (10 – 80uM), round, thick walled; contain endospores (2-5 uM diameter)

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Coccidioides immitis

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Arthroconidia are extremely infectious. Cultures must be handled cautiously, grown only in tubes. A biological safety cabinet must be used when handling suspected cultures. Do not make slide cultures of these organisms.

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Coccidioides immitis

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Coccidioides immitis

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These large spherules with a thick wall and filled with endospores are characteristic for Coccidioides immitis growing in tissues. The spherule at the left is bursting to expel its endospores, which grow and continue the infection.

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is endemic to the desert southwest of the U.S.

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Coccidioides immitis

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Infections:
– Blastomycosis

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Blastomyces dermatitidis

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Slow growth; 14 days to mycelial forms mature. Hold suspected cultures for 8 weeks. Process specimens immediately.

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Blastomyces dermatitidis

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Colony Morphology
– Initially yeast like, then white and cottony, turning brown or tan with age
– At 35 – 37, cream to tan, waxy yeast phase

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Blastomyces dermatitidis

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Microscopic:
– Septate hyphae with short or long conidiaphores – Round or pear shaped conidia – lollipop appearance – Older cultures have thick walled chlamydoconidia – Yeast cells have a “Broad base bud”

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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Slow growth; 15 - 20 days to mycelial forms mature. Hold suspected cultures for 8 weeks. Process specimens immediately

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Histoplasma capsulatum

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Infections:
– Histoplasmosis

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Histoplasma capsulatum

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Colony Morphology
– White to brown, fine dense cottony texture, reverse is white
– At 35 – 37, moist white yeast-like colonies may form. May take many
generations to convert to yeast form.

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Histoplasma capsulatum

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Microscopic:
– Septate hyphae with round to pear shaped microconidia, which are sometimes
spiny – After several weeks, large thick walled macroconidia form – Macroconidia can be confused with Sepedonium
– At 35 – 37, small budding cells may be seen

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Histoplasma capsulatum

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Histoplasma capsulatum inside macrophages

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Very slow growth; 21 days to mature

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Paracoccidiodes brasiliensis

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Infections:
– Paracoccidioidomycosis

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Paracoccidiodes brasiliensis

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Colony Morphology
– White heaped compact, folded glabrous; turns brown with age
– At 35 – 37, cream to tan, moist and soft, becomes waxy

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Paracoccidiodes brasiliensis

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Microscopic:
– Septate hyphae with intercalary and terminal chlamydospores
– Few microconidia along the hyphae
– At 35 – 37, large round thickwalled cells from with single or multiple buds (ship’s wheel)

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Paracoccidiodes brasiliensis

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Paracoccidiodes brasiliensis

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Paracoccidiodes brasiliensis

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Only true pathogen in Penecillium genus
• Only Penecillium species that is dimorphic

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Penicillium marneffei

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Infections:
– Systemic infection in immunocompromized individuals
– Disseminated disease is typically fatal

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Penicillium marneffei

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Colony Morphology
– Sparse green aerial and reddish brown vegetative hyphae and production of a red diffusible pigment

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Penicillium marneffei

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Microscopic:
– Yeast-like cells detected in Wright-stained smears from skin
lesions or biopsy specimens.
– Cells resemble those of H. capsulatum
– Oval to cylindrical measuring 3 – 6 um long and may have a cross wall

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Penicillium marneffei

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Penicillium marneffei Other Tests

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Exoantigen and PCR tests

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Penicillium marneffei

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Penicillium marneffei

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other tests for Paracoccidiodes brasiliensis

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Convert mold to yeast phase

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other tests for Histoplasma capsulatum

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- DNA Probes are available
– Exoantigen testing
– Convert mold to yeast phase

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other tests for Blastomyces dermatitidis

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-- DNA Probes are available
– Exoantigen testing
– Convert mold to yeast phase

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other tests for Coccidioides immitis

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– DNA Probes are available
– Immuno-diffusion for exoantigen

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Mode of transmission of systemic mycosis

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Inhalation of infected conidia

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Coccidioides immitis

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can be isolated from soil, decaying vegetation,
and animal dung. It is commonly isolated as
a contaminant.

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Malbranchea sp.

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Malbranchea sp.

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Due to the existence of arthroconidia
and the disjunctor cells, the two genera ________ & ________ are similar microscopically

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Malbranchea and Coccidioides

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grow moderately rapidly at 25°C. They are raised or flat, with or without furrows, and powdery,
woolly, or cottony in texture. The color of the colony may be white, orange, buff, tan, brown, or dark golden

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Malbranchea

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endemic in North America. Mississippi,
Ohio and Missouri valleys

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Blastomyces dermatitidis

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25°C- Septate hyaline hyphae and unbranched short conidiophores are observed. Conidiophores at right angles to hyphae. The conidia are unicellular and solitary.
37°C- budding yeast cells. The yeast cells refractile walls and a broad base attaching the bud to the parent cell.

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Blastomyces dermatitidis

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25°C - The growth rate is slow to moderately rapid. The texture is membranous and downy to woolly. The surface color is white to beige and reverse is pale to brownish.
37°C - texture is typically creamy and yeast-like. It appears granular to verrucose on the surface.
The color of the colony is white to beige.

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Blastomyces dermatitidis

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Microscopic mold phase looks similar to B dermatitidis, is not biphasic

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Scedosporium apiospermum

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endemic in the Tennessee- Ohio- Mississippi river valleys

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Histoplasma capsulatum

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At 25°C - Hyphae: septate + hyaline produce hyphae-like conidiophores which arise at right angles to the parent has macro- and microconidia. Macroconidia are tuberculate, thick-walled, round, unicellular, hyaline, lg w/ of fingerlike projections macroconidia aka tuberculochlamydospores or
macroaleurioconidia.

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Histoplasma capsulatum

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At 25°C - Colonies slow growing, granular to cottony. white, becomes buff brown with age. not sensitive to cycloheximide From the reverse, yellowish orange color. Sabouraud dextrose agar (SDA), brain heart infusion agar
(BHIA) enhance growth. At 37°C- Creamy, slowly growing, moist yeast-like infected tissues, in vitro on enriched media, such as BHIA containing 5-10% blood.

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Histoplasma capsulatum

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Microconidia (microaleurioconidia) are unicellular, hyaline and round, with a smooth or
rough wall. At 37°C - Narrow-based, ovoid, budding yeast cells are formed. Yeasts of var.
capsulatum are smaller than (2-4 μm)
those of var. duboisii (12-15 μm)

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Histoplasma capsulatum

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differs from Histoplasma capsulatum by not being dimorphic, not forming microconidia

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Sepedonium sp.

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25°C - hyphae are often sterile If present,
conidia are oval, unicellular, truncate + with a broad base and rounded apex. They are located along the hyphae. Arthroconidia and intercalary chlamydospores may also be
observed. 37°C- multiple buds surrounding the whole surface of the mother yeast cell. This
appearance resembles a steering wheel.

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Paracoccidiodes brasiliensis

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25:Colonies are filamentous, slow growing, leathery, flat to wrinkled, woolly, cottony or
glabrous to velvety. The front color is white cream, tan or brown and the reverse color is
yellowish brown to brown.
37:Colonies are yeast-like, white, heaped, wrinkled or folded.

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Paracoccidiodes brasiliensis

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Blastomyces dermatiditis

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Blastomyces dermatiditis

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Histoplasma capsulatum macroconidia and microconidia

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Scedosporium apiospermum

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Scedosporium apiospermum