Deck 47: Laboratory Methods in Basic Mycology

Question 1

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

A)vegetative mycelium.
B)germ tubes.
C)reproductive hyphae.
D)aerial mycelia.

Answer 1

D
The mycelium penetrates the culture media or other substrate and consists of hyphae with various purposes. The portion extending above the substrate surface is known as aerial mycelium, which can give rise to fruiting bodies from which asexual spores are produced.

Question 2

The simplest type of sporulation is the development of a spore directly from the vegetative hyphae. Arthroconidia are formed directly from the hyphae by fragmentation through the points of septation . When mature, they appear as square, rectangular, or barrel-shaped, thick-walled cells. These result from the simple fragmentation of the hyphae into spores, which are easily dislodged and disseminated into the environment.
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?

A)Arthroconidia
B)Chlamydoconidia
C)Ascospores
D)Ascoconidia

Answer 2

B
Chlamydoconidia (chlamydospores) are round, thick-walled spores formed directly from the differentiation of hyphae in which there is a concentration of protoplasm and nutrient material. These appear to be resistant resting spores produced by the rounding up and enlargement of the cells of the hyphae. Chlamydoconidia may be intercalary (within the hyphae) or terminal (on the end of hyphae).

Question 3

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?

A)dematiaceous fungi
B)Zygomycetes
C)hyaline fungi
D)Ascomycetes

Answer 3

B
To assist persons working in clinical microbiology laboratories with the identification of clinically important fungi, Koneman and Roberts have suggested the use of a practical working schema designed to assist in the recognition of fungi most commonly encountered in clinical specimens and those that are strictly pathogenic.

Question 4

Optimal recovery of filamentous fungi from blood specimens requires

A)an automated blood culture system.
B)the lysis-centrifugation system.
C)filteration through a 0.45-µm membrane filter.
D)a biphasic blood culture system.

Question 5

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

A)mycelium.
B)hyphae.
C)germ tubes.
D)pseudohyphae.

Question 6

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

A)the growth rate.
B)colonial morphologic features such as color and texture.
C)microscopic morphologic features such as shape, method of production, and arrangement of spores.
D)biochemical reactions.

Question 7

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

A)Dermatophytes
B)Zygomycetes
C)Dimorphic fungi
D)Dematiaceous fungi

Question 8

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

A)pseudohyphae.
B)a germ tube.
C)ascospore.
D)a bud scar.

Question 9

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

A)sporangiophores
B)zygospores
C)zygoconidiaphores
D)conidiophores

Question 10

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

A)hyphae.
B)germ tubes.
C)pseudohyphae.
D)mycelium.

Question 11

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

A)Arthroconidia.
B)Chlamydoconidia.
C)ascospores.
D)ascocarps.

Question 12

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

A)binary fission.
B)unisexual division.
C)budding.
D)outpouch germing.

Question 13

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

A)vegetative mycelium.
B)aerial mycelia.
C)reproductive hyphae.
D)germ tubes.

Question 14

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

A)dermatophytes.
B)Zygomycetes.
C)dimorphic fungi.
D)dematiaceous fungi.

Question 15

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

A)media with and without blood enrichment.
B)incubation at 35° C.
C)relative humidity in the range of 10% to 20%.
D)the use of decontamination and concentration methods.
E)All of the above are correct.

Question 16

Features of the fungi as a group include the following:

A)the presence of chitin in the cell wall.
B)the presence of ergosterol in the cell membrane.
C)reproduction by means of spores, either asexually or sexually.
D)heterotopic nature.
E)All of the above are correct.

Question 17

The term dematiaceous is used to describe

A)molds that have septate hyphae.
B)molds that have pauciseptate hyphae.
C)the presence of pigmentation within the hyphae or the spores.
D)the absence of pigmentation within the hyphae or the spores.

Question 18

The term hyaline is used to describe

A)molds that have septate hyphae.
B)molds that have pauciseptate hyphae.
C)the presence of pigmentation within the hyphae or the spores.
D)the absence of pigmentation within the hyphae or the spores.

Question 19

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

A)budding.
B)unisexual division.
C)binary fission.
D)outpouch germing.

Question 20

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

A)microconidia.
B)macroconidia.
C)conidiophores.
D)phialides.

Question 21

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

A)Coccidioides immitis.
B)Blastomyces dermatitidis.
C)Histoplasma capsulatum.
D)Paracoccidioides brasiliensis.

Question 22

Mycelium can be defined as

A)loose intertwined network of tubelike projections from which the fungus obtains the nutrients for growth.
B)tubelike projections that are the basic structural unit of the molds.
C)premature germ tubes.
D)a fungal element that is produced when buds elongate and fail to dissociate.

Question 23

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

A)Cunninghamella.
B)Absidia.
C)Mucor.
D)Rhizopus.

Question 24

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

A)Dermatophytes
B)Zygomycetes
C)Dimorphic fungi
D)Dematiaceous fungi

Question 25

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

A)Coccidioides immitis.
B)Blastomyces dermatitidis.
C)Histoplasma capsulatum.
D)Paracoccidioides brasiliensis.

Question 26

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

A)pseudohyphae.
B)germ tube.
C)ascospore.
D)bud scar.

Question 27

The reproductive process known as budding is that which involves

A)cell wall expansion and mitosis, followed by a new cell wall septum created between the two newly formed nuclei.
B)a portion of the fungus extending above the substrate surface to give rise to fruiting bodies from which asexual spores are borne.
C)a weakening and outpouching of the yeast cell wall and then formation of a cell wall septum between the mother and daughter yeast cells.
D)the sexual union of two mother cells to produce a daughter cell that eventually separates from the mother cells.

Question 28

The genus Microsporum is characterized by

A)large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia.
B)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.
C)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.
D)spherical, teardrop-shaped microconidia and rough, club-shaped, thick-walled macroconidia with 8 to 10 septa borne on short conidiophores.

Question 29

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

A)Cunninghamella.
B)Absidia.
C)Mucor.
D)Rhizopus.

Question 30

Hyphae can be defined as

A)loose intertwined network of tubelike projections from which the fungus obtains the nutrients for growth.
B)tubelike projections that are the basic structural unit of the molds.
C)premature germ tubes.
D)a fungal element that is produced when buds elongate and fail to dissociate.

Question 31

Vegetative mycelium are those that serve what main purpose?

A)Nutrient absorption and water exchange
B)Penetration of host cells
C)Transfer of genetic material from cell to cell
D)Give rise to fruiting bodies from which asexual spores are borne

Question 32

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

A)tinea nigra.
B)black piedra.
C)eumycotic mycetoma.
D)chromoblastomycosis.

Question 33

The genus Microsporum can be easily recognized by the presence of large (8 to 15 × 35 to 150 μm), spindle-shaped, rough-walled macroconidia with thick (up to 4 μm) walls that contain 4 or more septa . The exception is Microsporum nanum, which characteristically produces macroconidia having two cells. Microconidia, when present, are small (3 to 7 μm) and club-shaped, and are borne on the hyphae, either laterally or on short conidiophores.
The genus Epidermophyton is characterized by

A)large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia.
B)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.
C)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.
D)spherical, teardrop-shaped microconidia and rough, club-shaped, thick-walled macroconidia with 8 to 10 septa borne on short conidiophores.

Question 34

Binary fission is the process of reproduction in yeast that involves

A)cell wall expansion and mitosis, followed by a new cell wall septum created between the two newly formed nuclei.
B)a portion of the fungus extending above the substrate surface to give rise to fruiting bodies from which asexual spores are borne.
C)a weakening and outpouching of the yeast cell wall and then formation of a cell wall septum between the mother and daughter yeast cells.
D)the sexual union of two mother cells to produce a daughter cell that eventually separates from the mother cells.

Question 35

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

A)Dermatophytes
B)Zygomycetes
C)Dimorphic fungi
D)Dematiaceous fungi

Question 36

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

A)tinea nigra.
B)black piedra.
C)eumycotic mycetoma.
D)chromoblastomycosis.

Question 37

Aerial mycelia are those that serve what main purpose?

A)Nutrient absorption and water exchange
B)Penetration of host cells
C)Transfer of genetic material from cell to cell
D)Give rise to fruiting bodies from which asexual spores are borne

Question 38

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

A)Trichophyton
B)Epidermophyton
C)Microsporum canis
D)All of the above are correct.

Question 39

The genus Trichophyton is characterized by

A)large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia.
B)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.
C)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.
D)spherical, teardrop-shaped microconidia and rough, club-shaped, thick-walled macroconidia with 8 to 10 septa borne on short conidiophores.

Question 40

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

A)Coccidioides immitis.
B)Blastomyces dermatitidis.
C)Histoplasma capsulatum.
D)Paracoccidioides brasiliensis.

Question 41

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

A)hyaline molds.
B)pauciseptate molds.
C)dematiaceous molds.
D)nigraceous molds.

Question 42

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

A)Alternaria
B)Zygomycetes
C)Cladosporium
D)Microsporum

Question 43

The simplest type of sporulation is the development of a spore directly from the vegetative hyphae. Arthroconidia are formed directly from the hyphae by fragmentation through the points of septation . When mature, they appear as square, rectangular, or barrel-shaped, thick-walled cells. These result from the simple fragmentation of the hyphae into spores, which are easily dislodged and disseminated into the environment.
Chlamydoconidia are produced by

A)hyphae fragmentation through the points of septation.
B)the rounding up and enlargement of the terminal cells of the hyphae in which there is a concentration of protoplasm and nutrient material.
C)the union of two matching types of Zygomycetes.
D)ascocarps that are multiplied by binary fission.

Question 44

Arthroconidia are produced by

A)hyphae fragmentation through the points of septation.
B)the rounding up and enlargement of the terminal cells of the hyphae in which there is a concentration of protoplasm and nutrient material.
C)the union of two matching types of Zygomycetes.
D)ascocarps that are multiplied by binary fission.

Question 45

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

A)Alternaria
B)Acremonium
C)Cladosporium
D)Microsporum

Question 46

Rough-walled spores called zygospores are formed by

A)progressive cleavage during maturation within the sporangium.
B)rupture of the sporangial wall.
C)the rounding up and enlargement of the terminal cells of the hyphae.
D)the union of two matching types of Zygomycetes.

Question 47

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?

A)Alternaria
B)Zygomycetes
C)Cladosporium
D)Microsporum

Question 48

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

A)media with and without blood enrichment.
B)incubation at 30° C.
C)relative humidity in the range of 10% to 50%.
D)21 to 30 days of incubation time.
E)All of the above are correct.

Question 49

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

A)Cunninghamella.
B)Absidia.
C)Mucor.
D)Rhizopus.

Question 50

Microconidia can be defined as

A)conidia that have divided into many smaller conidia.
B)large, usually multiseptate and club- or spindle-shaped spores.
C)large, elbow-shaped, rough-walled spores.
D)small, unicellular, round, elliptical, or pyriform.

Question 51

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

A)The growth rate
B)Colonial morphologic features such as color and texture
C)Microscopic morphologic features such as shape, method of production, and arrangement of spores
D)A combination of the characteristics given in above is used.

Question 52

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

A)Dermatophytes
B)Zygomycetes
C)Dimorphic fungi
D)Dematiaceous fungi

Question 53

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

A)Dermatophytes
B)Zygomycetes
C)Dimorphic fungi
D)Dematiaceous fungi

Question 54

Features of the fungi as a group include the following:

A)the presence of chitin in the cell wall.
B)the absence of ergosterol in the cell membrane.
C)reproduction by means of transduction and germination.
D)autotrophic nature.
E)All of the above are correct.

Question 55

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

A)Cunninghamella.
B)Absidia.
C)Mucor.
D)Rhizopus.

Question 56

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

A)hyaline molds.
B)pauciseptate molds.
C)dematiaceous molds.
D)nigraceous molds.

Question 57

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

A)Dermatophytes
B)Zygomycetes
C)Dimorphic fungi
D)Dematiaceous fungi

Question 58

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

A)An automated blood culture system
B)The lysis-centrifugation system
C)Filteration through a 0.45-µm membrane filter
D)A biphasic blood culture system

Question 59

Macroconidia can be defined as

A)microconidia that have swollen and are ready to produce hyphae.
B)large, usually multiseptate and club- or spindle-shaped spores.
C)large elbow-shaped rough-walled spores.
D)large, ribbonlike hyphae with phialides.

Question 60

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

A)Cunninghamella.
B)Absidia.
C)Mucor.
D)Rhizopus.

Question 61

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

A)Coccidioides immitis.
B)Blastomyces dermatitidis.
C)Histoplasma capsulatum.
D)Paracoccidioides brasiliensis.

Question 62

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

A)tinea nigra.
B)black piedra.
C)eumycotic mycetoma.
D)chromoblastomycosis.

Question 63

Match the fungus with its description. Choose from the following:
a.Large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia
b.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.
c.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.d.spherical, teardrop-shaped microconidia and rough, club-shaped, thick-walled macroconidia with 8 to 10 septa borne on short conidiophores.
Microsporum

Question 64

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

A)tinea nigra.
B)black piedra.
C)eumycotic mycetoma.
D)dermatophycosis.

Question 65

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?

A)Coccidioides immitis
B)Blastomyces dermatitidis
C)Histoplasma capsulatum
D)Paracoccidioides brasiliensis

Question 66

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

A)Coccidioides immitis.
B)Blastomyces dermatitidis.
C)Histoplasma capsulatum.
D)Paracoccidioides brasiliensis.

Question 67

Match the fungus with its description. Choose from the following:
a.Large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia
b.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.
c.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.d.spherical, teardrop-shaped microconidia and rough, club-shaped, thick-walled macroconidia with 8 to 10 septa borne on short conidiophores.
Epidermophyton

Question 68

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

A)Trichophyton.
B)Epidermophyton.
C)Microsporum canis.
D)All of the above are correct.

Question 69

Match the fungus with its description. Choose from the following:
a.Large spindle-shaped, rough-walled macroconidia with thick walls that contain 4 to 15 septa and small club-shaped microconidia
b.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.
c.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.d.spherical, teardrop-shaped microconidia and rough, club-shaped, thick-walled macroconidia with 8 to 10 septa borne on short conidiophores.
Trichophyton