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MEDICAL MICROBIOLOGY > Mycology > Flashcards

Mycology Flashcards

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Biology 101 flashcards USMLE® Step 1 flashcards
1
Q

True or False.

All fungi are able to grow as yeasts and molds.

A

False.

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2
Q

True or False.

Although fungi are eukaryotes, they lack mitochondria.

A

False.

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3
Q

True or False.

Fungi are photosynthetic.

A

False.

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4
Q

True or False.

Fungi have one or more nuclei or chromosomes.

A

True

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5
Q

True or False.

Few fungi posses cell membranes.

A

False

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6
Q

True or False.

Pseudohyphae are produced by all yeasts.

A

False

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7
Q

True or False.

Molds produce hyphae that may or may not be partitioned with cross-walls or septa.

A

True

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8
Q

True or False.

Conidia are produced by sexual reproduction.

A

False. Asexual Reproduction.

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9
Q

True or False.

Most yeasts reproduce by budding and lack cell walls.

A

False. They have cell walls

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10
Q

True or False.

Most pathogenic dimorphic molds produce hyphae in the host and yeasts at 30 degrees Celsius

A

False

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11
Q

True or False.

The major components of fungal cell walls are proteins such as chitin, glucans, and mannans.

A

False

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12
Q

True or False.

The cell wall is no essential for fungal viability or survival.

A

False

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13
Q

True or False.

Ligands associated with the cell walls of certain fungi mediate attachment to host cells.

A

True

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14
Q

True or False.
Fungal cell wall components are the targets for the major classes of antifungal antibiotics, such as the polyenes and azoles.

A

False. Plasma membrane.

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15
Q

True or False.

Fungal cell wall components rarely stimulate an immune response.

A

False

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16
Q

A 54-year-old man developed a slowly worsening headache followed by gradual, progressive weakness in his right arm. A brain scan revealed a cerebral lesion. At surgery an abscess surrounded by granulomatous material was found. Sections of the tissue and subsequent culture showed darkly pigmented septate hyphae indicating phaeohyphomycosis. This infection may be cause by species of which genus below?

a. Aspergillus
b. Cladophialophora
c. Coccidioides
d. Mallasezia
e. Sporothrix

A

b. Cladophialophora

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17
Q

A35-year-oldmanisafarmerinatropicalareaofWestAfrica. He developed a persistent scaly papule on his leg. Ten months later a new crop of wart-like purplish scaly lesions appeared. These lesions slowly progressed to a cauliflower-like appearance. Chromoblastomycosis (chromomycosis) was diagnosed. Which statement regarding this disease is most correct?
(A) In tissue, the organisms convert to spherical cells that reproduce by fission and exhibit transverse septations.
(B) The etiologic agents are endogenous members of the mam-
malian flora and possess melanized cell walls.
(C) The disease is caused by a single species.
(D) Most infections are systemic.
(E) Most infections are acute and clear spontaneously.

A

(A) In tissue, the organisms convert to spherical cells that reproduce by fission and exhibit transverse septations.

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18
Q

A 42-year-old HIV-positive male, originally from Vietnam but now residing in Tucson, Arizona, presents with a painful ulcerative lesion on his upper lip (cheilitis). A biopsy was obtained, and the histopathologic slide (hematoxylin and eosin stain) revealed spherical structures (20–50 μm in diameter) with thick refractory cell walls. What is the likely disease consistent with this finding?
(A) Infection with Penicillium marneffei
(B) Cryptococcosis
(C) Blastomycosis
(D) Coccidioidomycosis
(E) No diagnostic significance

A

(D) Coccidioidomycosis

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19
Q

A 47-year-old man with poorly controlled diabetes mellitus developed a bloody nasal discharge, facial edema, and necrosis of his nasal septum. Culture of his cloudy nasal secretions yielded Rhizopus species. What is the most important implication of this finding?
(A) No diagnostic value because this mold is an airborne contaminant.
(B) Consider treatment for rhinocerebral mucormycosis (zygomycosis).
(C) Strongly suggestive of ketoacidosis.
(D) Strongly suggestive of HIV infection.
(E) The patient has been exposed to indoor mold contamination.

A

(B) Consider treatment for rhinocerebral mucormycosis (zygomycosis).

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20
Q 
An 8-year-old boy develops a circular dry, scaly, and pruritic lesion on his leg. What is the diagnostic significance of observ- ing branching, septate, nonpigmented hyphae in a potassium hydroxide/calcofluor white preparation of a scraping from this skin lesion?
(A) Chromomycosis
(B) Dermatophytosis
(C) Phaeohyphomycosis
(D) Sporotrichosis
(E) No diagnostic significance
A

(B) Dermatophytosis

21
Q

True or False.

Patients receiving bone marrow transplants are not at risk for systemic candidiasis.

A

False.

22
Q

True or False.

Patients with impaired or low numbers of neutrophils and monocytes are not at risk for systemic candidiasis.

A

False

23
Q

True or False.

Patients with any form of diabetes have enhanced resistance to candidiasis.

A

False.

24
Q

True or False.

Patients with AIDS frequently develop mucocutaneous candidiasis, such as thrush.

A

True.

25
Q

True or False.

Pregnancy lowers the risk of candidal vaginitis.

A

False.

26
Q

True or False.

Chronic infections of dermatophytosis are associated with zoophilic dermato­phytes, such as Microsporum canis.

A

False.

27
Q

True or False.

Acute infections of dermatophytosis are associated with zoophilic dermatophytes, such as M canis.

A

True

28
Q

True or False.

Chronic infections of dermatophytosis are associated with anthropophilic dermatophytes, such as M canis

A

False

29
Q

True or False.

Acute infections of dermatophytosis are associated with anthropophilic dermatophytes, such as M canis

A

False.

30
Q

True or False.
Histoplasma capsulatum typically requires less than 48 hours of incubation to yield positive cultures from clinical specimens.

A

False.

31
Q

True or False.
Since many saprobic (nonpathogenic) molds resemble dimorphic mycotic agents in culture at 30°C, the identification of putative dimorphic pathogenic fungi must be confirmed by conversion to the tissue form in vitro or by the detection of species-specific antigens or DNA sequence analysis.

A

True.

32
Q

True or False.
Molds are routinely speciated by a battery of physiologic tests, such as the ability to assimilate various sugars.

A

False.

33
Q

True or False.

A positive germ tube test provides a rapid presumptive identification of Candida glabrata.

A

False

34
Q

True or False.

Budding yeast cells and abundant pseudohyphae are typical of Pneumocystis jiroveci.

A

False.

35
Q

A 28-year-old female sex worker from southern California complained of headaches, dizziness, and occasional episodes of “spacing out” during the past 2 weeks. A lumbar puncture revealed reduced sugar, elevated protein, and 450 mononuclear leukocytes per milliliter. She was seropositive for HIV. Her history is compatible with fungal meningitis due to Cryptococcus neoformans, Coccidioides posadasii, or a species of Candida. Which one of the following tests is confirmatory?
(A) Meningitis due to Coccidioides posadasii would be confirmed by a positive test of the CSF for cryptococcal capsular antigen.
(B) Meningitis due to Cryptococcus neoformans would be conf irmed by a positive test of the CSF for complement fixation antibodies to coccidioidin.
(C) Meningitis due to a species of Candida would be confirmed by the microscopic observation of oval yeast cells and pseudohyphae in the CSF.
(D) Meningitis due to Coccidioides posadasii would be confirmed by a positive skin test to coccidioidin.

A

(C). Meningitis due to a species of Candida would be confirmed by the microscopic observation of oval yeast cells and pseudohyphae in the CSF.

36
Q

Which statement about phaeohyphomycosis is correct?
(A) The infection only occurs in immunocompetent patients.
(B) Infected tissue reveals branching, septate nonpigmented hyphae.
(C) The causative agents are members of the normal microbial f lora and can be isolated readily from the skin and mucosa of healthy persons.
(D) Phaeohyphomycosis may exhibit several clinical manifestations, including subcutaneous or systemic disease, as well as sinusitis.
(E) Cases rarely respond to treatment with itraconazole.

A

(D) Phaeohyphomycosis may exhibit several clinical manifestations, including subcutaneous or systemic disease, as well as sinusitis.

37
Q 
A  37-year-old  male  with  AIDS,  currently  living  in  Indianapolis, Indiana,  presented  with  osteomyelitis  of  the  left  hip.  A  needle biopsy  of  the  bone  marrow  was  obtained,  and  the  calcofluor white  smear  revealed  a  variety  of  myelogenous  cells,  monocytes, and  macrophages  containing  numerous  intracellular  yeast  cells that  were  elliptical  and  approximately  2  ×  4  µm.  What  is  the most likely diagnosis? 
(A)  Blastomycosis 
(B)  Candidiasis 
(C)  Cryptococcosis 
(D)  Histoplasmosis 
(E)  No diagnostic significance
A

(D) Histoplasmosis

38
Q 
The  potassium  hydroxide  examination  of  sputum  from  a  heart transplant  patient  with  fever  and  pulmonary  infiltrates  contains  oval  budding  yeast  cells  and  pseudohyphae.  What  is  the diagnostic significance? 
(A)  Aspergillosis 
(B)  Candidiasis 
(C)  Hyalohyphomycosis 
(D)  Phaeohyphomycosis 
(E)  No diagnostic significance
A

(E) No diagnostic significance

39
Q

A middle-aged male resident of southern California received a liver transplant. During the following months, he gradually developed fatigue, weight loss, cough, night sweats, dyspnea, and a nonhealing subcutaneous nodule on his nose. The chest radiograph revealed hilar lymphadenopathy and diffuse infiltrates. Direct examination and culture of a respiratory specimen were negative. Skin tests with PPD, blastomycin, coccidioidin, and histoplasmin were negative. Serologic test results were as follows: Negative serum test for cryptococcal capsular antigen in blood, positive immunodiffusion test for serum precipitins to fungal antigen F, and negative immunodiffusion tests for precipitins to antigens h, m, and A. Serum tests for fungal complement fixation antibodies were negative for Blastomyces dermatitidis, as well as both the mycelial and yeast antigens of Histoplasma capsulatum but yielded a titer of 1:32 to coccidioidin. Which interpretation of these data is the most tenable? (A) Clinical and serologic findings are inconclusive. (B) Clinical and serologic findings are most consistent with active disseminated histoplasmosis. (C) Clinical and serologic findings are most consistent with active disseminated blastomycosis. (D) Clinical and serologic findings are consistent with active disseminated coccidioidomycosis. (E) Clinical and serologic findings exclude a diagnosis of blastomycosis, histoplasmosis, and coccidioidomycosis.

A

(D) Clinical and serologic findings are consistent with active disseminated coccidioidomycosis.

40
Q

Which statement regarding aspergillosis is correct?
(A) Patients with allergic bronchopulmonary aspergillosis rarely have eosinophilia.
(B) Patients receiving parenteral corticosteroids are not at risk for invasive aspergillosis.
(C) The diagnosis of pulmonary aspergillosis is frequently established by culturing Aspergillus from the sputum and blood.
(D) The clinical manifestations of aspergillosis include local infections of the ear, cornea, nails, and sinuses.
(E) Bone marrow transplant recipients are not at risk for invasive aspergillosis.

A

(D) The clinical manifestations of aspergillosis include local infections of the ear, cornea, nails, and sinuses.

41
Q

Which statement regarding sporotrichosis is correct?
(A) The most common etiologic agent is Pseudallescheria boydii (Scedosporium apiospermum).
(B) The etiologic agent is a dimorphic fungus.
(C) The ecology of the etiologic agent is unknown.
(D) Most cases are subcutaneous and nonlymphangitic.
(E) Most patients are immunocompromised.

A

(B) The etiologic agent is a dimorphic fungus.

42
Q 
A  24-year-old,  HIV-negative  migrant  worker  from  Colombia presented  with  a  painful  ulcerative  lesion  on  the  tongue.  The edge  of  the  lesion  was  gently  scraped  and  a  calcofluor  whitepotassium  hydroxide  smear  revealed  tissue  cells,  debris,  and several  large,  spherical,  multiply  budding  yeast  cells.  Based  on this observation, what is the most likely diagnosis? 
(A)  Blastomycosis 
(B)  Candidiasis 
(C)  Coccidioidomycosis 
(D)  Histoplasmosis 
(E)  Paracoccidioidomycosis
A

(E) Paracoccidioidomycosis

43
Q

Which statement about blastomycosis is correct?
(A) Similar to other endemic mycoses, this infection occurs equally in men and women.
(B) Infection starts in the skin, and the organisms commonly disseminate to the lungs, bone, genitourinary tract, or other sites.
(C) The disease is endemic to certain areas of South America.
(D) In tissue, one finds large, thick-walled, single budding yeast cells with broad connections between the parent yeast and bud.
(E) All cases require treatment with amphotericin B.

A

(D) In tissue, one finds large, thick-walled, single budding yeast cells with broad connections between the parent yeast and bud.

44
Q

Which statement regarding dermatophytosis is correct?
(A) Chronic infections are associated with zoophilic dermatophytes, such as Trichophyton rubrum.
(B) Acute infections are associated with zoophilic dermatophytes, such as T rubrum.
(C) Chronic infections are associated with anthropophilic dermatophytes, such as T rubrum.
(D) Acute infections are associated with anthropophilic dermatophytes, such as T rubrum.

A

(C) Chronic infections are associated with anthropophilic dermatophytes, such as T rubrum.

45
Q

Which statement regarding paracoccidiomycosis is not correct?
(A) The etiologic agent is a dimorphic fungus.
(B) Most patients acquired their infections in South America.
(C) Although the infection is acquired by inhalation and is initiated in the lungs, many patients develop cutaneous and mucocutaneous lesions.
(D) The vast majority of patients with active disease are males.
(E) The etiologic agent is inherently resistant to amphotericin B.

A

(E) The etiologic agent is inherently resistant to amphotericin B.

46
Q 
Your  kidney  transplant  patient  has  developed  nosocomial  systemic  candidiasis,  but  the  patient’s  isolate  of  Candida  glabrata is  resistant  to  fluconazole.  A  reasonable  alternative  would  be oral administration of: 
(A)  Flucytosine 
(B)  Posaconazole 
(C)  Griseofulvin 
(D)  Amphotericin B
A

(B) Posaconazole

47
Q 
Which one  of  the  following  antifungal  drugs  does  not  target  the biosynthesis of ergosterol in the fungal membrane? 
(A)  Voriconazole 
(B)  Itraconazole 
(C)  Terbinafine 
(D)  Fluconazole 
(E)  Micafungin
A

(E) Micafungin

48
Q 
Which  one  of  the  following  pathogenic  yeasts  is  not  a  common member of the normal human  flora or microbiota? 
(A)  Candida tropicalis 
(B)  Malassezia globosa 
(C)  Cryptococcus neoformans 
(D)  Candida glabrata 
(E)  Candida albicans
A

(C) Cryptococcus neoformans

MEDICAL MICROBIOLOGY (3 decks)

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