Micro 201unit 5

Which characteristic is used in the diagnostic laboratory to help identify clinically significant molds?

A combination of the characteristics given in above is used.

A fungus culture is growing a mold that has rhizoids that originate between sporangiophores. The sporangia are pyriform and have a funnel-shaped area at the junction of the sporangium and the sporangiophore. This fungus should be identified as

Absidia.

A mold that has septate hyphae, conidia in clusters, and no pigment would likely belong to which group of fungi?

Acremonium

Using the Koneman and Roberts working schema for identifying clinical mold isolates, a mold that has dark-pigmented septate hyphae and multicelled conidia would likely belong to which group of fungi?

Alternaria

Hyphae fragmentation through the points of septation produces what type of spore?

Arthroconidia.

A KOH preparation of respiratory secretions of a 78-year-old man reveals large, spherical, thick-walled yeast cells 8 to 15 µm in diameter, usually with a single bud that is connected to the parent cell by a broad base. Which fungus will likely be isolated from the culture?

Blastomyces dermatitidis

Large, spherical, thick-walled yeast cells 8 to 15 µm in diameter, usually with a single bud that is connected to the parent cell by a broad base, usually indicates infection with

Blastomyces dermatitidis.

The rounding up and enlargement of the terminal cells of the hyphae in which there is a concentration of protoplasm and nutrient material produces what type of spore?

Chlamydoconidia

A mold that has dark-pigmented, septate hyphae and single-celled conidia would likely belong to which group of fungi?

Cladosporium

The presence of nonbudding, thick-walled spherules containing granular material in a KOH preparation of cerebrospinal fluid usually indicates infection with

Coccidioides immitis.

The presence of nonbudding, thick-walled spherules, 20 to 200 µm in diameter, containing either granular material or numerous small, nonbudding endospores, usually indicates infection with

Coccidioides immitis.

A white fungus is growing on fungal medium with cycloheximide and chloramphenicol additives on which nail scrapings were inoculated. Which fungi is likely growing?

Dermatophytes

Which group of fungi produce infections that involve the superficial areas of the body, including the hair, skin, and nails?

Dermatophytes

Aerial mycelia are those that serve what main purpose?

Give rise to fruiting bodies from which asexual spores are borne

Sporangiophores that are singularly produced or branched and have at their tip a round sporangium filled with sporangiospores and the absence of rhizoids or stolons would usually indicate infection with

Mucor.

Vegetative mycelium are those that serve what main purpose?

Nutrient absorption and water exchange

The presence of large, round or oval, multiply budding yeast cells, which resemble a "mariner's wheel," detected on direct microscopic examination usually indicates infection with

Paracoccidioides brasiliensis.

The presence of large, round or oval, multiply budding yeast cells, which resemble a "mariner's wheel," usually indicates infection with

Paracoccidioides brasiliensis.

A fungus culture is growing a mold that has unbranched sporangiophores with rhizoids that appear at the base of the sporangiophore at the point where the stolon arises. This fungus should be identified as

Rhizopus.

Unbranched sporangiophores with rhizoids that appear at the point where the stolon arises at the base of the sporangiophore would usually indicate infection with

Rhizopus.

Unbranched sporangiophores with rhizoids that appear at the point where the stolon arises, at the base of the sporangiophore would usually indicate infection with

Rhizopus.

Laboratories that have a high incidence of dimorphic fungi recovered from blood specimens should use which system of recovery?

The lysis-centrifugation system

The genus ___________ is capable of invading the hair, skin, and nails.

Trichophyton

The same dermatophyte is isolated from plucked hairs, skin scrapings, and nails of an older patient. The most likely identification is

Trichophyton.

A KOH preparation on a sputum specimen from a patient on immune suppressive therapy shows large, broad, nonseptate hyphae. Choose the most likely agent.

Zygomycetes

Irregular, large, ribbonlike hyphae with no apparent septa, saclike fruiting structures, and rhizoids are seen in which group of molds?

Zygomycetes

Using the Koneman and Roberts working schema for identifying clinical mold isolates, a mold which has hyphae that appear to be predominantly nonseptate would likely belong to which group of fungi?

Zygomycetes

Which group of molds characteristically produces large, ribbonlike hyphae that are irregular in diameter and contain only occasional septa?

Zygomycetes

Which group of molds is referred to as the "aseptate" fungi?

Zygomycetes

Immunocompromised patients, particularly those who have uncontrolled diabetes mellitus and those who are receiving prolonged corticosteroid, antibiotic, or cytotoxic therapy, are at greatest risk of developing infection with

Zygomycetes.

The tubular outpouching that occurs in some yeast cells without constriction at its base is referred to as

a germ tube.

The reproductive process known as budding is that which involves

a weakening and outpouching of the yeast cell wall and then formation of a cell wall septum between the mother and daughter yeast cells.

The portion of the fungus extending above the substrate surface and which often gives rise to fruiting bodies from which asexual spores are borne is known as

aerial mycelia.

The process of reproduction in yeast that begins with cell wall expansion and mitosis and is followed by a new cell wall septum created between the two newly formed nuclei is called

binary fission.

A recent immigrant from Latin America presents with a fungal infection of the hair of the scalp and pubic hair. The fungus culture reveals a dematiaceous fungi. The most likely diagnosis would be

black piedra.

The process of reproduction in yeast that begins with a weakening and outpouching of the yeast cell wall and then formation of a cell wall septum between the mother and daughter yeast cells is called

budding.

Binary fission is the process of reproduction in yeast that involves

cell wall expansion and mitosis, followed by a new cell wall septum created between the two newly formed nuclei.

Molds that have pigmentation within the hyphae or the spores are referred to as

dematiaceous molds.

A chronic granulomatous infection that is characterized by swelling, purplish discoloration, tumorlike deformities of the subcutaneous tissue, and multiple sinus tracts that drain pus

eumycotic mycetoma.

A recent immigrant from Africa presents with tumorlike deformities of the subcutaneous tissue and multiple sinus tracts that drain pus containing granules. The fungus culture reveals a hyaline septate fungi. The most likely diagnosis would be

eumycotic mycetoma.

Molds that have no pigmentation within the hyphae nor the spores are referred to as

hyaline molds.

Arthroconidia are produced by

hyphae fragmentation through the points of septation.

The basic structural unit of the molds are tubelike projections known as

hyphae.

The genus Microsporum is characterized by

large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia.

Macroconidia can be defined as

large, usually multiseptate and club- or spindle-shaped spores.

Mycelium can be defined as

loose intertwined network of tubelike projections from which the fungus obtains the nutrients for growth.

Large, usually multiseptate and club- or spindle-shaped spores are called

macroconidia.

Optimal recovery of fungi from specimens in the clinical microbiology laboratory requires

media with and without blood enrichment.

Optimal recovery of fungi from most types of specimens in the clinical microbiology laboratory requires

media with and without blood enrichment. incubation at 30° C. relative humidity in the range of 10% to 50%. 21 to 30 days of incubation time.

In most instances the most definitive means for identification of clinically significant molds is

microscopic morphologic features such as shape, method of production, and arrangement of spores.

The term hyaline is used to describe

molds that have pauciseptate hyphae.

The loose intertwined network of basic structural units of the molds which penetrates the substrate from which it obtains the necessary nutrients for growth is called the

mycelium.

The genus Epidermophyton is characterized by

numerous smooth, thin-walled, club-shaped, multiseptate macroconidia, which are rounded at the tip and are borne singly on a conidiophore or in groups of two or three, no microconidia, and numerous chlamydoconidia.

The genus Trichophyton is characterized by

predominate spherical, teardrop-shaped or club-shaped microconidia and smooth, club-shaped, thin-walled macroconidia with 8 to 10 septa borne singly at the terminal ends of hyphae or on short conidiophores.

The fungal element that is produced when buds elongate and fail to dissociate is referred to as a

pseudohyphae.

Microconidia can be defined as

small, unicellular, round, elliptical, or pyriform.

Optimal recovery of filamentous fungi from blood specimens requires

the lysis-centrifugation system.

Features of the fungi as a group include the following:

the presence of chitin in the cell wall.

Features of the fungi as a group include the following:

the presence of chitin in the cell wall. the presence of ergosterol in the cell membrane. reproduction by means of spores, either asexually or sexually. heterotopic nature.

The term dematiaceous is used to describe

the presence of pigmentation within the hyphae or the spores.

Chlamydoconidia are produced by

the rounding up and enlargement of the terminal cells of the hyphae in which there is a concentration of protoplasm and nutrient material.

Rough-walled spores called zygospores are formed by

the union of two matching types of Zygomycetes.

A superficial skin infection, caused by Exophiala werneckii, manifested by blackish brown macular patches on the palm of the hand or sole of the foot is called

tinea nigra.

Hyphae can be defined as

tubelike projections that are the basic structural unit of the molds.

The nutrient-absorbing and water-exchanging portion of the fungus is called

vegetative mycelium.

One type of sexual reproduction produces rough-walled spores called ______________, which are formed by the union of two matching types of Zygomycetes.

zygospores