Mycology

Question 1

What are the dimorphic fungi?

Answer 1

Histo/Blasto/Cocci/Paracocci
Penicillium
Sporothrix
Chromoblastomycoses broadly

Question 2

Fungal culture media

Answer 2

Nonselective: SAB, BBHI,
Selective: Mycosel (contains cyclohexamide), birdseed (stains phenol oxidase producers)

Question 3

Fungal special stains

Answer 3

PAS - Nonselectively stains cell walls
GMS - As above
Mucicarmine - Crypto, rhinosporidium
Fontana-masson - Crypto & other melanin producers
India ink - Crypto

Calcofluor white: Chitin/cellulose, nonspecific
Lactophenol cotton blue: Wet preps, nonspecific

Question 4

Histoplasma

Answer 4

Bird/bat guano. Necrotizing granulomas. Intra-macrophage.

Mold: Tuberculated microconidia (studded wheel)
Yeast: 2-4uM narrow budding

Urine antigen test available

Question 5

Blastomyces

Answer 5

Mold: Pear-shaped (lollipop) conidia
Yeast: 8-20um double-walled, broad-budding

Question 6

Coccidioides

Answer 6

Note: Immitis and posadasii are identical.

Mold: Barrel-shaped arthroconidia. DO NOT CULTURE.
Yeast: 50um spherule with endospores (mucicarmine-negative)

Question 7

Rhinosporium

Answer 7

India, waterborne, mass-forming. Actually a parasite.

200um spherules with endospores (mucicarmine+)

Question 8

Paracoccidioides

Answer 8

Brazil!

Mold: Pear-shaped conidia
Yeast: 10-20um mother-daughter cysts (Mariner wheel)

Question 9

Eumycotic mycetoma

Answer 9

Mass-forming cutaneous lesion of usually black molds. Traumatic inoculation. “Madura foot”

Usually actinomyces (clumps of filamentous bacteria) or pseudallescheria (pear-shaped conidia).

Question 10

Chromoblastomycosis

Answer 10

Subcutaneous infection with dematiaceous fungi (melanin-producers). Granulomatous. `

Usually Fonsecacea, phialophora, or cladosporium.

Yeast: Copper/medlar bodies. Large, septated/multicellular.

Question 11

Sporothrix

Answer 11

Rose-thorn traumatic inoculation. Lymphangitic spread with buboes.

Mold: Daisy-wheel rosetting conidia.
Yeast: 2-5uM “cigar bodies”

Question 12

Lobomyces

Answer 12

Keloidal verrucae.

Chains of globose cells.

Cannot be cultured.

Question 13

Fusarium

Answer 13

Mold: “Banana”/canoe-shaped conidia. In tissue, appears to have swollen hyphal varicosities.

Question 14

Candida (species!)

Answer 14

Albicans: Most common. Forms germ tubes (CORNMEAL AGAR)
Glabrata: Elderly. Resists fluconazole. No germ tubes. Trehalose assimilation.
Krusei: Resists fluconazole. No germ tubes.
Auris: Multidrug resistant.
Parapsilopsis: Children.

Triphasic morphology with pseudohyphae. May speciate with FISH or biochemical ID panels, or sequencing. UREASE NEGATIVE

Question 15

Tinea versicolor

Answer 15

Malassezia furfur: Lipophilic organism, only grows with oil. Associated with IV lipids, catheters.

“Spaghetti & meatball” morphology. 2-4um yeast. Urease+

Question 16

Microsporum

Answer 16

Microsporum canis: Dogs. Macroconidia with tapered ends.

Microsporum gypseum: Rare. Macroconidia with rounded ends.

Question 17

Trichophyton

Answer 17

Rubrum: Feet, nails. Overall most common dermatophyte.
Tonsurans: Scalp

Microconidia (no macroconidia), “birds on a wire”

Question 18

Epidermophyton floccosum

Answer 18

Beaver-tail macroconidia

Question 19

Cryptococcus

Answer 19

Neoformans mainly (Gattii emerging). Bird guano, ubiquitous in soil. Cyclohexamide sensitive.

Yeast only. 2-20uM (variable!). Thick capsule, mucoid colonies.

Mucicarmine, Fontana-Masson.

Question 20

Hyalohyphomycoses

Answer 20

Tissue infection by hyaline hyphal fungi.

Includes ASPERGILLUS, fusarium, paecilomyces.

Do not try to speciate unless fruiting bodies are present (rare, requires airspace)

Question 21

Phaeohyphomycoses

Answer 21

Tissue infection with black molds (melanin producing)

Includes alternaria, curvularia, pseudallescheria, scedosporium.

Brown-red. Do not try to differentiate on H&E.

Question 22

Alternaria

Answer 22

Black mold (pigmented). Inhibited by cycloheximide

Hand-grenade or honey-wand conidia.

Common environmental allergen. Seen in pap smears.

Question 23

Curvularia

Answer 23

Black mold (pigmented)

Boomerang rounded conidia.

Question 24

Pseudallescheria

Answer 24

Black mold (pigmented)

Pear-shaped conidia. Nondescript.

Question 25

Zygomycetes

Answer 25

Rhizopus: Most common, has nodal rhizomes.
Mucor: Next most common, has no rhizomes.
Absidia: Rare, has internodal rhizomes.

Rapid growers (“lid-lifters”). Mince, do not grind.

Question 26

Urease positive fungi

Answer 26

Cryptococcus

Malassezia

Question 27

Aspergillus - Diagnosis

Answer 27

Rarely found in blood culture.

Galactomannan immunoassay

Question 28

Penicillium marneffei

Answer 28

Southeast asia. Opportunist.

In plate: Red diffusible pigment.
Mold: Slender “skeleton-hand” phialide & conidia

Question 29

Aspergillus species

Answer 29

Fumigatus: Green. Uniseriate phialide, conidia growing “up”. 45C growth. Cyclohexamide sensitive.
Niger: Black. Full circumference, black conidia.
Flavus: Yellow.
Terreus: Brown.

Question 30

Syncephalastrum racemosum

Answer 30

No phialides