Yeasts Week 15

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chlamydoconidia

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pseudohyphae &blastoconidia

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conidia

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spore

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arthroconidia

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Colony Morphology
– Cream colored, pasty, smooth.
– On blood agar, may form “feet” at edges of colony

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Candida albicans

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Microscopic: – Pseudohyphae, some true hyphae – Clusters of round blastoconidia at the septa of pseudohyphae – Large, thick walled, usually single terminal chlamydospores
– Germ Tube positive
– Urease negative (variable)

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Candida albicans

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Candida albicans

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Candida albicans

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Colony Morphology
– Cream colored
– On blood agar, may show wrinkling at edges
of colony

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Candida tropicalis

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Microscopic: – Pseudohyphae, some true hyphae – blastoconidia singly or in small groups
anywhere along pseudohyphae – Few tear drop shaped Chlamydospores may
be present
– Germ Tube negative
– Urease negative

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Candida tropicalis

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Candida tropicalis

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Candida tropicalis

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Candida tropicalis

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Infections in bloodstream,urogenital tract, normal flora• Colony Mor – Cream colored, sm yeast like -Microscopic: – Oval yeast cells w/ single terminal budding • No pseudohyphae
•Germ Tube neg – Urease neg

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Candida glabrata

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Candida (Torulopsis) glabrata

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• normal flora
• Colony Morph – Cream colored
• Microscopic: – Round blastoconidia
– Urease positive
– Growth on Bird Seed Agar (Niger Seed Agar): White (negative)
– Caffeic acid disk test: negative (alternative to Bird Seed Agar)

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Cryptococcus albidus

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Cryptococcosis or normal flora • C: Flat or slightly heaped, shiny, moist, mucoid – blood agar, may show wrinkling at edges Micro – Yeast cells round, dark walled, budding – No hyphae
– Capsules may be – Bird seed agar / Caffeic Acid test Positive – Germ Tube negative – Urease pos– India ink for capsule

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Cryptococcus neoformans

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Cryptococcus sp.

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Cryptococcus sp.

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Cryptococcus neoformans produces
phenoloxidase, The conversion of caffeic acid in the nigerseed agar test is in
keeping with this metabolic scheme.
The active ingredient in nigerseed agar is the
melanin-producing compound, 3,4
dihydrocinnamic acid (caffeic acid).

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caffeic acid test for

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Cryptococcus neoformans

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The API 20-C strip

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carbohydrate yeast id tests

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– Disease in severely compromised hosts
& normal flora
• Colony Morphology: White, moist, yeast-like
– Submerged hyphae may form on aging
• Microscopic: True hyphae – Arthroconidia
– No blastoconidia
• Germ Tube negative – Urease negative

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Geotrichum

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Geotrichum candidum

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Geotrichum sp.

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C:Usually pink or coral, orange to red Soft, moist, may be mucoid
• Micro Budding cells are round to oval Rare pseudohyphae– Faint capsule maybe

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Rhodoturola

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Rhodotorula rubrum

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Rhodotorula rubrum

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– Disease in immuno-compromised hosts
– Some species cause white piedra
– Found as normal flora skin, nails, and mouth

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Trichosporon sp.

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Colony Morphology
– Yeast like. Cream colored, moist and soft
– Dries with age, may crack the agar
• Microscopic:
– Hyphae and pseudohyphae present
– Blastoconidia, singly or in short chains
– Arthroconidia in older cultures

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Trichosporon sp.

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Trichosporon sp.

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Trichosporon beigellii

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Trichosporon sp.

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Colony Morph– Variable: “white fuzzy” – No
yeast phase, forms a spherule in tissue
• Microscopic: Coarse Septate branched

hyphae Thick walled barrel shaped arthroconidia Arthroconidia alternate in the hyphae w/
empty cells that break away – Malbranchea
may be confused w/

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Coccidioides immitis

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Spherules are lg, round, thick walled; contain endospores – DNA Probes are available – Immuno-diffusion 4 exoantigen

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Coccidioides immitis

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Coccidioides immitis

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Coccidioides immitis

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Coccidioides immitis

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Colony Morph – Variable: white, beige,
orange, pinkish. Granular, powdery or
woolly. – Light reverse • Microscopic:
– Coarse Septate branched hyphae, no
conidiophores – Arthroconidia not swollen
or thick walled. – Arthroconidia alternate in
the hyphae w/ empty cells that break away

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Malbranchea sp.

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Malbranchea sp.

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Malbranchia sp.

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Colony Morph Initially yeast like, then white & colony, turning brown or tan w/ age – At 35 – 37, cream to tan, waxy yeast phase • Micro: – Septate hyphae w/ short or long conidiaphores Round or pear shaped conidia lollipop appearance Older cultures have thick walled chlamydoconidia Scedosporium apiospermum

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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Blastomyces dermatitidis

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The colony is cottony and powdery with a pale brown color. Mature growth occurred in 6 days on SDA. There was no growth on media containing cycloheximide. The organism did not convert to a yeast form when cultured at 37
degrees. The reverse of the colony is brown.

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Chrysosoporium sp.

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Chrysosoporium sp.

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Chrysosoporium sp.

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• Colony Morph – White- brown, fine dense
colony texture, reverse white –At 35–37,
moist white yeast‐like colonies may form. May
take many generations to convert •Micro: Septate hyphae w/ round topear shaped microconidia, which are sometimes spiny After

several wks, lg thick walled macroconidia form

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Histoplasma capsulatum

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– Macroconidia can be confused w/ Sepedonium
– At 35– 37, small budding cells may be seen

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Histoplasma capsulatum

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Histoplasma capsulatum

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Histoplasma capsulatum

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Histoplasma capsulatum

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Histoplasma capsulatum

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Colony Morph: White & waxy then becoming colony. Reverse is white – At 37, little or no growth. • Micro: Septate hyphae w/ single or branched conidiophores – Conidia are round, thick walled, & rough & knobby
– No microconidia formed, no yeast phase

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Sepedonium sp.

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Sepedonium sp.

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Sepedonium sp.

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Colony Morph: White heaped compact,
folded glabrous; turns brown w/ age – At
35–37, cream to tan, moist and soft, becomes
waxy • Micro: Septate hyphae w/ intercalary
& terminal chlamydospores– Few microconidia
along the hyphae – At 35–37, lg round thick walled cells fr w/ single or multiple buds (ship’s
wheel)

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Paracoccidiodes brasilienses

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Paracoccidiodes brasilienses

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Paracoccidiodes brasilienses

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Paracoccidiodes immitis

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Paracoccidiodes immitis