question

Hyphae

answer

Tubular filaments that are the microscopic units of the fungi and intertwine to form the mycelium.

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Mycelium

answer

Intertwining structure of fungi composed of tubular filaments or hyphae.

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Septate hyphae

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Hyphae with separations or walls.

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Aseptate hyphae

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No walls or septate.

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Blastoconidia

answer

Asexual conidia produced by formation of conidia by simple budding from mother’s cells hyphae, or pseudohyphae.

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Chlamydoconidia

answer

Thick walled asexual conidia that are formed during unfavorable conditions and germinate when environment improves; greater in diameter than hyphae and may be observed at hyphal tip, within the hyphae, and on the sides of the hyphae.

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Arthroconidia

answer

Asexual spores formed by fragmentation of mycelia into rectangular barrel shaped or cask shaped thick walled spores.

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Sporangiospores

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Asexual spore contained in a saclike structure in which spores are formed and held (sporangium); the sporangium is housed in a specialized hyphal stalk or sporangiophore.

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Ascospores

answer

Type of specialized spore involved in sexual reproduction of some fungi in which two to eight spores are contained in a sac like ascus.

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Thallophytes

answer

Those members of the plant family that possess true nuclei lack stems and roots, do not possess chlorophyll, and absorb nutrients from the environment.

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Dimorphic fungi

answer

Fungi that possess both a yeast phase at 37oC and a mold or mycelial phase at 25oC.

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Fungi imperfecti

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Imperfect fungi that do not exhibit a sexual phase and produce spores asexually from the mycelium.

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Conidia

answer

Asexual spores produced by some fungi either singly or multiply in long chains or clusters by specialized hyphae known as conidiophores.

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Macroconidia

answer

Large multicellular club oval or spindle shaped asexual fungal spores that are usually septate.

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Microconidia

answer

Small unicellular round elliptical or piriform asexual fungal spores.

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Sporangiospore

answer

Asexual fungal spores contained in a sac or sporangium that are produced terminally on sporangiophores or aseptate hyphae.

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Deuteromycetes

answer

Division in the botanical taxonomy that includes most medically important fungi characterized by septate hyphae and asexual reproduction.

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Endothrix

answer

Fungal infection of the hair involving the inside of the hair shaft.

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Ectothrix

answer

Fungal infection of the hair shaft involving the outside of the hair shaft.

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Mold phase

answer

Mycelial phase of a dimorphic fungus that is observed on Sabouraud’s dextrose agar at 25C. The saprophytic phase is usually seen in nature.

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Yeast phase

answer

Yeast phase of a dimorphic fungus that is observed in tissue or invasive in vivo and grows on enriched media at 37oC.

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Vegetative portion

answer

The mycelium consists of a thallus (vegetative portion) which grows in or on a substrate and absorbs water and nutrients.

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Reproductive area

answer

The aerial portion with fruiting bodies.

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Sexual reproduction

answer

Reproduction by fungi involving ascospores (example). Requires the formation of a special structure so that fertilization or nuclear fission can occur.

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Oospores

answer

Sexual reproductive spore in some fungi that involves fusion of cells from two separate non-identical hyphae.

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Zygospores

answer

Sexual reproductive spore of some fungi that involves the fusion of two identical cells arising from the same hyphae.

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Basidiospores

answer

Type of specialized spore involved in sexual reproduction of some fungi; the spores are contained in a club shaped basidium.

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Dermatiaceous fungi

answer

A group of dark slow growing fungi that are found on vegetation and are associated with subcutaneous mycoses, including the development of chronic warty tumor like lesions of the feet and lower legs.

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Topography

answer

Best observed from the reverse side and may be flat, heaped, or folded.

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Texture

answer

Best observed in a cross section and it is usually related to the length of the aerial hyphae.

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Chromoblastomycosis

answer

Type of subcutaneous fungi infection caused by the dermatiaceous fungi; generally these infections are transmitted thru a puncture wound or skin trauma involving fungus contaminated vegetation.

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Mycetoma

answer

Chronic granulomatous infection of the cutaneous and subcutaneous tissues and bone characterized by tumor like deformities of the subcutaneous tissue with abscesses, draining sinuses, and granulomatous pus.

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Phaeohyphomycosis

answer

Darkly pigmented molds.

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Hyalohyphomycetes

answer

Hyaline mold (nonpigmented). Opportunist infection. Found in soil and vegetation.

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Saline wet mount

answer

Quick simple method to observe fungal elements including budding yeast, hyphae, and pseudo hyphae.

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Lactophenol cotton blue (LCB)

answer

Used to visualize microscopic fungal morphology by imparting a blue color to the cell walls.

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KOH Preparation (Potassium Hydroxide)

answer

Dissolve keratin in skin hair and nail specimens to observe the fungal elements in the specimen.

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Cellufluor

answer

A brightening agent added to KOH to bind chitin in the fungal cell wall and provides excellent contrast in the preparation when examined with a fluorescent microscope.

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India ink

answer

The nigrosin prep to identify the capsule of the Cryptococcus neoformans organism in CSF.

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Silver stain

answer

Methenamine silver nitrate stain, which is useful for the screening of clinical specimens providing good contrast and staining for the fungal elements. Fungi appear outlined in black against a pale background.

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Periodic acid Schiff (PAS)

answer

Stains the hyphae of molds and also some yeast by oxidizing the hydrosol in the carbohydrates of the cell walls of the organisms to form aldehydes, which react with fuschin dye and form a pink purple complex.

question

typical general guidelines for fungal specimen collection techniques:

answer

Very similar to those for bacterial infections. Includes the use of sterile collection methods and devices to avoid contamination and provide sufficient quantity for culture.

question

Sabouraud Dextrose Agar (SDA)

answer

General isolation medium with peptone and glucose.

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Dermatophyte test medium (DTM)

answer

Used for the recovery of dermatophytes from specimens contaminated with fungi or bacteria.

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Brain heart infusion (BHI)

answer

Useful for isolation of agents of systemic mycoses. It is most useful in the isolation of pathogenic fungi from sterile specimens.

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Sabouraud Dextrose Agar with Cycloheximide & Chloramphenicol (SDA-CC)

answer

contains cycloheximide which inhibits many saprophytic contaminating fungi while the chloramphenical is a bacterial inhibitor.

question

Tease mount

answer

Tease preparation of a wet mount with Lactophenol blue in which a portion of actively growing fungus is examined.

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Slide culture

answer

Culture prepared on agar which is on a slide.

question

Germ tube

answer

Serum with inoculated specimen examined after 2 hour incubation in CO2 to view germ tubes of yeast.

question

Carbohydrate assimilation

answer

Can provide a definite identification for yeast and yeast like organisms.

question

Rapid Urease

answer

The production of the enzyme urease is useful in the preliminary identification of mainly yeast.

question

BHI with antibiotics

answer

Isolation of pathogenic fungi exclusive of dermatophytes. Useful for specimens that may be contaminated with bacteria or saprophytic fungi

question

BHI biphasic

answer

Recovery of fungi from blood or bone marrow.

question

Mycosel agar

answer

Isolation of hair, nail and skin infections specimens similar to DTM.

question

Birdseed agar

answer

For isolation for Cryptococcus neoformans which produces phenol oxidase breaking up the medium causing growth of brown melanin colonies.

question

Cornmeal agar

answer

Stimulation of conidia and chlamydospore (chlamydoconidia) production in Candida species. Used to identify Candida albicans.

question

Potato dextrose agar

answer

Stimulation of conidia production in the fungi.

question

Rice medium

answer

For identification of M. audouinii.

question

Trichophyton agar

answer

Nutritional requirement for differentiation of Trichophyton.

question

Urea agar

answer

Detection of urease production by Cryptococcus neoformans and differentiation of Trichophyton mentagrophytes from Trichophyton rubrum.

question

Tinea barbae
typical infection site

answer

Ringworm of the beard.

question

Tinea capitis
typical infection site

answer

Ringworm of the head/scalp.

question

Tinea corporis
typical infection site

answer

Ringworm of the body

question

Tinea crusis
typical infection site

answer

Ringworm of the groin.

question

Tinea pedis
typical infection site

answer

Ringworm of the foot or athlete's foot.

question

Tinea unguium
typical infection site

answer

Ringworm of the nails.

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Microsporum audouinii
macroscopic and microscopic descriptions

answer

Cottony and white, rare conidia, form chlamydoconida like swellings terminally on hyphae. Once a leading cause of tinea capitis in children. Fluoresces with Wood’s light.

question

Microsporum canis
macroscopic and microscopic descriptions

answer

Macroconidia are spindle shaped with thick walls, spiny ends, and may be elongated. Colonies are fluffy and white; reverse is lemon-yellow. Causes ringworm in cats, dogs, and other animals.

question

Microsporum. gypseum
macroscopic and microscopic descriptions

answer

Thick walled conidia. Forms tan colonies. Found in soil.

question

Epidermophyton floccosum
macroscopic and microscopic descriptions

answer

Smooth, thin walled macroconidia. Yellow to yellow-tan small colonies.

question

Trichophyton mentagrophytes
macroscopic and microscopic descriptions

answer

Macroconidia are thin walled, smooth, and cigar shaped. Produced singly on hyphae. Rapid grower compared to other dermatophytes. Produces flat white cream colored colonies with a red brown underside.

question

Trichophyton rubrum
macroscopic and microscopic descriptions

answer

Produces white fluffy granular colonies with a deep cherry red or burgundy pigment on the underside. Hard to find macroconidia. Typically see microconidia on hyphae.

question

Trichophyton tonsurans
macroscopic and microscopic descriptions

answer

Forms rust colored pigment on reverse side of agar. Agent of epidemic tinea capitis in children (including U.S.).

question

Germ tubes:+

answer

C. albicans

question

Wide capsules

answer

C.neoformans

question

Blastoconidia present

answer

Candida sp., Saccharomyces, Cryptococcus sp.,Rhodotorula

question

Arthroconidia present

answer

Trichosporon

question

Urease: +

answer

Cryptococcus sp., Rhodotorula

question

Terminal chlamydo

answer

C. albicans

question

Red pigmented on SAB

answer

Rhodotorula

question

Ascospores

answer

Saccharomyces

question

Blastomyces
typical clinical significance

answer

Causes blastomycosis.
Involves skin, lung, and kidney infections.
Produces flu-like symptoms leading to pulmonary, skin, and organ involvement. May be rapidly fatal. Known as Gilchrist’s disease, North American blastomycosis, and Chicago disease.

question

Coccidioides
typical clinical significance

answer

Causes Coccidioidomycosis.
Involves inhalation of arthroconidia of the dimorphic fungus.
Produces pulmonary involvement and allergic reactions.

question

Histoplasma
typical clinical significance

answer

-Causes histoplasmosis (also called reticuloendothelia cytomycosis, cave disease, spelunker’s disease, and Darlings disease).
-Produces an infection caused by inhalation of microconidia in soil contaminated with excreta from birds found in the Mississippi river valley. -Involves lungs, liver, and spleen. -Organisms may remain in the host for years (may be reactivated).

question

Paracoccidioides
typical clinical significance

answer

Causes paracoccidioidomycosis. Produces a chronic fungal infection caused by P. brasiliensis and is characterized by ulcers of the mouth and lymph node involvement. Prefers cooler areas of the body to grow (will spread to other areas of the body if immunocompromised).

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Sporothrix schenckii
typical clinical significance

answer

Causes lymphocutaneous sporotrichosis a chronic subcutaneous fungal infection characterized by skin ulcers, subcutaneous nodules, and lymphatic infection. Found in soil and decaying vegetation.

question

Fonsecaea pedrosoi
typical clinical significance

answer

Causes Chromoblastomycosis of the feet and lower legs.

question

Penicillium marneffei
typical clinical significance

answer

Only true pathogen in this genus. Common cause of systemic infection (organs and skin lesions) in immunocompromised patients. Dimorphic. Yeast like cells in body. Mold form may have green aerial hyphae and reddish-brown vegetative hyphae with a red pigment.

question

Sporothrix schenckii
typical microscopic identify characteristics

answer

Small, cigar shaped yeast at 35oC. Room temperature culture shows conidia in a rosette pattern at the ends of conidiophores.

question

Histoplasma capsulatum
typical microscopic identify characteristics

answer

Small, round, and oval within monocytes and neutrophils on peripheral or bone marrow smears. Yeast at 35oC culture. Tuberculate macroconidia at room temperature culture.

question

Blastomyces dermatitidis
typical microscopic identify characteristics

answer

Round, oval yeast with broad based budding at 35oC. Room temperature culture shows microconidia (not diagnostic).

question

Paracoccidioides brasiliensis
typical microscopic identify characteristics

answer

Yeast at 35oC culture. Multiple budding yeast cells (mariner’s wheel) observed at room temperature culture

question

Coccidioides immitis
typical microscopic identify characteristics

answer

Large thick walled round spherules with endospores on tissue prep (may see at 37oC culture). Produces alternating staining arthroconidia (disjunctor cell) on culture.

question

State the division of fungi causing the majority of fungal infections:

answer

Deuteromycetes.

question

typical length of time fungal cultures are minimally held:

answer

Fungal cultures minimally held at least 2 to 4 weeks.

question

typical macroconidia for:
Microsporum canis

answer

Multiseptate macroconidia.

question

typical macroconidia for:
Trichophyton mentagrophytes

answer

Smooth club shaped thin walled macroconidia with 8-10 septate.

question

typical macroconidia for:
Histoplasma capsulatum

answer

Large thick walled knobby tuberculate macroconidia.

question

typical macroconidia for:
Epidermophyton floccosum

answer

Numerous club shaped smooth walled with 2-4 septate.

question

Absidia
microscopic identification

answer

Like Rhizopus but the sporangiophores arise between nodes from which rhizoids are formed.

question

Mucor:
microscopic identification

answer

Like rhizopus with no rhizoids.

question

Aspergillus:
microscopic identification

answer

Branching septate hyphae that terminate in a conidiophore that expands into a large spherical vesicle covered with stalks (sterigmata).

question

Rhizopus
microscopic identification

answer

Large broad nonseptae hyphae producing horizontal runners or stolons attaching at rhizoids with sporangiophores arising in clusters terminating in sporangia.

question

Penicillium
microscopic identification

answer

Septate hyaline hyphae with brush like conidiophores which give rise to phialides

question

Alternaria
microscopic identification

answer

Septate dermatiaceous conidiophores that branch with chains of brown conidia which are muriform and tapered

question

Fusarium
microscopic identification

answer

Two celled or multi-celled structures, smooth walled, fusiform, macroconidia resembling a banana.

question

Malassezia furfur:
-clinical significance
-common name given to the infection
-significant microscopic appearance
-significant growth characteristics:

answer

Causes tinea versicolor.
Appears as tight clusters of spherical yeast like cells.
Grows on SDA with olive oil in 2-4 days at 30oC producing creamy yeast like colonies.

question

Cladosporium carrionii:
-clinical significance
-common name given to the infection
-significant microscopic appearance
-significant growth characteristics:

answer

Causes chromoblastomycosis.
Appears as dark, long, branching conidiophores that give rise to chains of blastoconidia with septae hyphae. Cannot grow above 37oC.
-Fast growing gray black moist yeast like colony.

question

Fonsecaea pedrosoi:
-clinical significance
-common name given to the infection
-significant microscopic appearance
-significant growth characteristics:

answer

-Causes chromoblastomycosis.
-Slow growing, black/brown colony with black aerial mycelium.
-Dark septate hyphae with primary mycosis conidia at conidiophore tip.

question

Phialophora verrucosa:
-clinical significance
-common name given to the infection
-significant microscopic appearance
-significant growth characteristics:

answer

Causes chromoblastomycosis.
Fast growing, black/gray, dome shaped. Septate hyphae with short conidiophores that give rise to flask or cup shaped phialides with collarettes.

question

Sporothrix schenckii:
-clinical significance
-common name given to the infection
-significant microscopic appearance
-significant growth characteristics:

answer

-Causes sporotrichosis.
-Rapidly growing white paste like colony that becomes brown black and leathery.
-It is a dimorphic fungus with septate hyphae and pyriform conidia arranged in floweret form.

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