8.9 Mycology

Question 1

All of the following are examples of appropriate specimens for the recovery of fungi except:
A. Tissue biopsy
B. Cerebrospinal fluid
C. Aspirate of exudate
D. Swab

Answer 1

D. Swab

Question 2

For which clinical specimens is the KOH direct mount technique for examination of fungal elements used?
A. Skin
B. Cerebrospinal fluid
C. Blood
D. Bone marrow

Answer 2

A. Skin

Question 3

The India ink stain is used as a presumptive test for the presence of which organism?
A. Aspergillus niger in blood
B. Cryptococcus neoformans in CSF
C. Histoplasma capsulatum in CSF
D. Candida albicans in blood or body fluids

Answer 3

B. Cryptococcus neoformans in CSF

Question 4

Cutaneous disease involving skin, hair, and nails usually indicates an infection with a:
A. Dimorphic fungus
B. Dermatophyte
C. Mucorales (previously Zygomycetes)
D. Candida species

Answer 4

B. Dermatophyte

Question 5

What is the first step to be performed in the identification of an unknown yeast isolate?
A. Gram staining
B. India ink staining
C. Catalase test
D. Germ tube test

Answer 5

D. Germ tube test

Question 6

An isolate produced a constriction that was interpreted as a positive germ tube, but C. albicans was ruled out when confirmatory tests were performed. Which of the following fungi is the most likely identification?
A. Candida tropicalis
B. Cryptococcus neoformans
C. Candida glabrata
D. Rhodotorula rubra

Answer 6

A. Candida tropicalis

Question 7

Cornmeal agar with Tween 80 is used to identify which characteristic of an unknown yeast isolate?
A. Hyphae (true and pseudo)
B. Blastoconidia and arthroconidia
C. Chlamydoconidia
D. All of these options

Answer 7

D. All of these options

Question 8

Blastoconidia are the beginning of which structures?
A. Arthroconidia
B. Germ tubes
C. Pseudohyphae
D. True hyphae

Answer 8

C. Pseudohyphae

Question 9

An isolate from CSF growing on cornmeal agar produces the following structures:
Blastoconidia = + Pseudohyphae = Neg
Chlamydoconidia = Neg Arthroconidia= Neg
Which tests should be performed next?
A. Birdseed agar and urease
B. Germ tube and glucose
C. India ink and germ tube
D. All of these options

Answer 9

A. Birdseed agar and urease

Question 10

Which of the following yeast enzymes is detected using birdseed (niger seed) agar?
A. Phenol oxidase
B. Catalase
C. Urease
D. Nitrate reductase

Answer 10

A. Phenol oxidase

Question 11

Which of the following yeasts is characteristically positive for germ tube production?
A. Candida tropicalis
B. Candida kefyr (pseudotropicalis)
C. Cryptococcus neoformans
D. Candida albicans

Answer 11

D. Candida albicans

Question 12

Arthroconidia production is used to differentiate which two yeast isolates?
A. Candida albicans and Candida dubliniensis
B. Trichosporon cutaneum and Cryptococcus neoformans
C. Candida albicans and Candida tropicalis
D. Saccharomyces cerevisiae and Candida glabrata

Answer 12

B. Trichosporon cutaneum and Cryptococcus neoformans

Question 13

The urease test, niger seed agar test, and the germ tube test are all used for the presumptive identification of:
A. Rhodotorula rubra
B. Cryptococcus neoformans
C. Trichosporon cutaneum
D. Candida albicans

Answer 13

B. Cryptococcus neoformans

Question 14

Which of the following yeasts produces only blastoconidia on cornmeal Tween 80 agar?
A. Candida spp.
B. Trichosporon spp.
C. Geotrichum spp.
D. Cryptococcus spp.

Answer 14

D. Cryptococcus spp.

Question 15

Ascospores are formed by which yeast isolate?
A. Saccharomyces cerevisiae
B. Candida albicans
C. Cryptococcus neoformans
D. All of these options

Answer 15

A. Saccharomyces cerevisiae

Question 16

A germ tube–negative, pink yeast isolate was recovered from the respiratory secretions and urine of a patient with AIDS. Given the following results, what is the most likely identification?
CORNMEAL TWEEN 80 AGAR
Blastoconidia = + Pseudohyphae = Neg
Arthroconidia= Neg Urease = +
A. Candida albicans
B. Rhodotorula spp.
C. Cryptococcus spp.
D. Trichosporon spp

Answer 16

B. Rhodotorula spp.

Question 17

Terminal chlamydoconidia production is demonstrated by which Candida species?
A. Candida glabrata
B. Candida krusei
C. Candida albicans
D. Candida tropicalis

Answer 17

C. Candida albicans

Question 18

Carbohydrate assimilation tests are used for the identification of yeast isolates by inoculating media:
A. Free of carbohydrates
B. Free of niger seed
C. Containing carbohydrates
D. Containing yeast extract

Answer 18

A. Free of carbohydrates

Question 19

Yeast recovered from the urine of a catheterized patient receiving chemotherapy for cancer gave the following results:
CORNMEAL TWEEN 80 AGAR
Germ tube = +
Pseudohyphae = +
Terminal chlamydoconidia = +
Blastoconidia = +
Arthroconidia= Neg
What further testing is necessary?
A. Carbohydrate assimilation and urease
B. Urease and niger seed
C. Nitrate reductase and carbohydrate fermentation
D. No further testing is needed for identification

Answer 19

D. No further testing is needed for identification

Question 20

A blood agar plate inoculated with sputum from a patient with diabetes mellitus grew very few bacterial flora and a predominance of yeast. Given the following results, what is the most likely identification of the yeast isolate?
CORNMEAL TWEEN 80 AGAR
Germ tube = Neg
Arthroconidia = Neg
Pseudohyphae = +
Blastoconidia = + (arranged along pseudohyphae)
Chlamydoconidia = Neg
A. Candida tropicalis
B. Candida kefyr (pseudotropicalis)
C. Trichosporon cutaneum
D. Geotrichum candidum

Answer 20

A. Candida tropicalis

Question 21

Dimorphic molds are found in infected tissue in which form?
A. Mold phase
B. Yeast phase
C. Encapsulated
D. Latent

Answer 21

B. Yeast phase

Question 22

The mycelial form of which dimorphic mold produces thick-walled, rectangular, or barrel-shaped alternate arthroconidia?
A. Coccidioides immitis
B. Sporothrix schenckii
C. Histoplasma capsulatum
D. Blastomyces dermatitidis

Answer 22

A. Coccidioides immitis

Question 23

The yeast form of which dimorphic fungus appears as oval or elongated cigar shapes?
A. Coccidioides immitis
B. Sporothrix schenckii
C. Histoplasma capsulatum
D. Blastomyces dermatitidis

Answer 23

B. Sporothrix schenckii

Question 24

The mycelial form of H. capsulatum seen on agar resembles:
A. Sepedonium spp.
B. Penicillium spp.
C. Sporothrix spp.
D. Coccidioides spp

Answer 24

A. Sepedonium spp.

Question 25

The yeast form of which dimorphic mold shows a large parent yeast cell surrounded by smaller budding yeast cells?
A. Paracoccidioides brasiliensis
B. Sporothrix schenckii
C. Coccidioides immitis
D. Histoplasma capsulatum

Answer 25

A. Paracoccidioides brasiliensis

Question 26

Which group of molds can be ruled out when septate hyphae are observed in a culture?
A. Dematiaceous
B. Mucorales (formerly Zygomycetes)
C. Dermatophytes
D. Dimorphic molds

Answer 26

B. Mucorales (formerly Zygomycetes)

Question 27

Tinea versicolor is a skin infection caused by:
A. Malassezia furfur
B. Trichophyton rubrum
C. Trichophyton schoenleinii
D. Microsporum gypseum

Answer 27

A. Malassezia furfur

Question 28

Which of the following structures is (are) invaded by the genus Trichophyton?
A. Hair
B. Nails
C. Skin
D. All of these options

Answer 28

D. All of these options

Question 29

An organism cultured from the skin produces colonies displaying a cherry-red color on Sabouraud dextrose agar after 3 to 4 weeks and teardrop-shaped microconidia along the sides of the hyphae. The most likely identification is:
A. Trichophyton rubrum
B. Trichophyton tonsurans
C. Trichophyton schoenleinii
D. Trichophyton violaceum

Answer 29

A. Trichophyton rubrum

Question 30

Which Microsporum species causes an epidemic form of tinea capitis in children?
A. Microsporum canis
B. Microsporum audouinii
C. Microsporum gypseum
D. All of these options

Answer 30

B. Microsporum audouinii

Question 31

Microscopic examination of a fungus cultured from a patient with athlete’s foot showed large, smooth-walled, club-shaped macroconidia appearing singly or in clusters of two to three from the tips of short conidiophores. The colonies did not produce microconidia. What is the most likely identification?
A. Trichophyton spp.
B. Alternaria spp.
C. Epidermophyton spp.
D. Microsporum spp

Answer 31

C. Epidermophyton spp.

Question 32

Which Trichophyton species causes the favus type of tinea capitis seen in the Scandinavian countries and in the Appalachian region of the United States?
A. Trichophyton verrucosum
B. Trichophyton violaceum
C. Trichophyton tonsurans
D. Trichophyton schoenleinii

Answer 32

D. Trichophyton schoenleinii

Question 33

The hair baiting test is used to differentiate which two species of Trichophyton that produce red colonies on Sabouraud agar plates?
A. Trichophyton mentagrophytes and Trichophyton rubrum
B. Trichophyton tonsurans and Trichophyton schoenleinii
C. Trichophyton tonsurans and Trichophyton violaceum
D. Trichophyton verrucosum and Trichophyton rubrum

Answer 33

A. Trichophyton mentagrophytes and Trichophyton rubrum

Question 34

A mold that produces colonies with a dark brown, green-black, or black appearance of both the surface and reverse side is classified as a:
A. Dematiaceous mold
B. Dermatophyte
C. Hyaline mold
D. Dimorphic fungus

Answer 34

A. Dematiaceous mold

Question 35

A rapidly growing hyaline mold began as a white colony but soon developed a black “pepper” effect on the agar surface. The older colony produced a black matte, making it resemble a dematiaceous mold. What is the most likely identification?
A. Penicillium notatum
B. Aspergillus niger
C. Paecilomyces spp.
D. Scopulariopsis spp.

Answer 35

B. Aspergillus niger

Question 36

Which dematiaceous mold forms flask-shaped phialides, each with a flask-shaped collarette?
A. Phialophora spp.
B. Exophiala spp.
C. Wangiella spp.
D. All of these options

Answer 36

A. Phialophora spp.

Question 37

Which Aspergillus species, recovered from sputum or bronchial mucus, is the most common cause of pulmonary aspergillosis?
A. Aspergillus niger
B. Aspergillus flavus
C. Aspergillus fumigatus
D. All of these options

Answer 37

C. Aspergillus fumigatus

Question 38

A hyaline mold recovered from a patient with AIDS produced rose-colored colonies with lavender centers on Sabouraud dextrose agar. Microscopic examination showed multiseptate macroconidia appearing as sickles or canoes. What is the most likely identification?
A. Fusarium spp.
B. Wangiella spp.
C. Exophiala spp.
D. Phialophora spp.

Answer 38

A. Fusarium spp.

Question 39

Material from a fungus-ball infection produced colonies with a green surface on Sabouraud agar in 5 days at 30°C. Microscopic examination showed club-shaped vesicles with sporulation only from the top half of the vesicle. This hyaline mold is most probably which Aspergillus spp.?
A. Aspergillus niger
B. Aspergillus fumigatus
C. Aspergillus flavus
D. Aspergillus terreus

Answer 39

B. Aspergillus fumigatus

Question 40

A rapidly growing nonseptate mold produced colonies with a gray surface resembling cotton candy that covered the entire plate. Microscopic examination revealed sporangiophores arising between, not opposite, the rhizoids and producing pear-shaped sporangia. What is the most likely identification?
A. Lichtheimis (formerly Absidia) spp.
B. Penicillium spp.
C. Rhizopus spp.
D. Aspergillus spp.

Answer 40

A. Lichtheimis (formerly Absidia) spp.

Question 41

An India ink test was performed on CSF from a male patient with HIV infection. Many encapsulated yeast cells were seen in the centrifuged sample. Further testing revealed a positive urease test and growth of brown colonies on niger seed agar. The diagnosis of meningitis was caused by which yeast?
A. Candida albicans
B. Cryptococcus neoformans
C. Cryptococcus laurentii
D. Candida tropicalis

Answer 41

B. Cryptococcus neoformans

Question 42

A bone marrow sample obtained from an immunocompromised patient revealed small intracellular cells using a Wright stain preparation. Growth on Sabouraud dextrose agar plates of a mold phase at 25°C and a yeast phase at 37°C designates the organism as dimorphic. The mold phase produced thick, spherical tuberculated macroconidia. What is the most likely identification?
A. Histoplasma capsulatum
B. Sepedonium spp.
C. Sporothrix schenckii
D. Coccidioides immitis

Answer 42

A. Histoplasma capsulatum

Question 43

A lung biopsy obtained from an immunocompromised patient showed many “cups-haped” cysts (gray to black) in a foamy exudate (green background) using Gomori methenamine silver (GMS) stain. The organism cannot be cultured because it does not grow on routine culture media for molds. The patient was diagnosed with pneumonia resistant to antibiotic treatment. The most likely identification is:
A. Pneumocystis jirovecii (previously Pneumocystis carinii)
B. Histoplasma capsulatum
C. Sporothrix schenckii
D. Scopulariopsis spp.

Answer 43

A. Pneumocystis jirovecii (previously Pneumocystis carinii)

Question 44

Upon direct examination of a sputum specimen, several spherules that contained endospores were noted. Growth on Sabouraud–dextrose agar showed aerial mycelial elements. The septate hyphae produced barrel-shaped arthroconidia. What is the most likely identification?
A. Talaromyces (formerly Penicillium) marneffei
B. Scopulariopsis spp.
C. Cryptococcus neoformans
D. Coccidioides immitis

Answer 44

D. Coccidioides immitis

Question 45

A bone marrow specimen was obtained from an immunocompromised patient who tested positive for HIV. The organism grew rapidly at 3 days showing a mold form (at 25°C), displaying conidiophores with four to five terminal metulae with each having four to six phialides. The conidia at the end of the phialides were oval and in short chains. They appear as a fan or broom when viewing under 10× and 40× magnification. At 37°C, the yeast form grew more slowly, showing conidia that formed hyphal elements breaking at the septa to produce oval arthroconidia. This thermodimorphic mold is most likely:
A. Paecilomyces spp.
B. Talaromyces (formerly Penicillium) marneffei
C. Rhizomucor spp.
D. Aspergillus fumigatus

Answer 45

B. Talaromyces (formerly Penicillium) marneffei

Question 46

What is the specimen of choice for the initial diagnosis of P. jirovecii (carinii) in an immunocompromised patient, such as someone with AIDS?
A. Induced sputum
B. Open-thorax lung biopsy
C. CSF
D. Urine

Answer 46

A. Induced sputum

Question 47

A transplant patient is suspected of having invasive aspergillosis on the basis of clinical and radiological findings. Which specimen is best for the initial identification of aspergillosis by soluble antigen testing?
A. Blood culture
B. Lung biopsy
C. Serum or urine
D. Sputum

Answer 47

C. Serum or urine

Question 48

What is the most common cause of mucormycosis infection in humans?
A. Penicillium spp.
B. Candida albicans
C. Scopulariopsis spp.
D. Rhizopus spp.

Answer 48

D. Rhizopus spp.

Question 49

A thermally dimorphic fungus shows a filamentous mold form with tuberculate macroconidia at room temperature, and a yeast form above 35°C. Which organism best fits this description?
A. Histoplasma capsulatum
B. Paracoccidioides brasiliensis
C. Candida albicans
D. Coccidioides immitis

Answer 49

A. Histoplasma capsulatum

Question 50

SITUATION: After a vacation to the southwestern United States, a midwesterner complained of flulike symptoms with fever, chills, nonproductive cough, and chest pain. Microscopic examination of sputum, cleared with KOH, revealed large, thick-walled spherules containing endospores. Upon culture, the mold phase showed septate hyphae and alternating barrel-shaped arthroconidia. Which organism is most likely the cause of this pneumonia?
A. Coccidioides immitis
B. Histoplasma capsulatum
C. Paracoccidioides brasiliensis
D. Talaromyces (formerly Penicillium) marneffei

Answer 50

A. Coccidioides immitis

Question 51

Skin scrapings from a young male patient showed many yeast cells of oval and bottle-shapes with monopolar budding. The direct microscopic examination also showed hyphal elements with a “spaghetti and meatball” morphological appearance. The most likely identification of this yeast is?
A. Malassezia furfur
B. Candida glabrata
C. Candida albicans
D. Cryptococcus neoformans

Answer 51

A. Malassezia furfur

Question 52

Microscopically, Scopulariopsis spp. resemble Penicillium spp. Which of the following best differentiates the two?
A. Nonseptate hyphae and foot cells
B. Brush-like conidiophores and large echinulate conidia
C. No hyphae and no phialides
D. Growth at 45°C.

Answer 52

B. Brush-like conidiophores and large echinulate conidia

Question 53

A fast-growing (2–5 days) culture of fluffy white to blue-green colonies from a respiratory specimen obtained from an immunocompromised ICU patient showed septate hyphae with many conidiophores. The tips of the conidiophores expand into large dome-shaped vesicles with bottle-shaped phialides covering the upper half or two-thirds of its surface. Long chains of small conidia form a columnar mass on the surface. At the base of the conidiophore, a “foot cell” is seen attaching the conidiophore to the septate hyphae. The most likely organism is?
A. Penicillium spp.
B. Scopulariopsis spp.
C. Aspergillus fumigatus
D. Paecilomyces spp.

Answer 53

C. Aspergillus fumigatus