Microbiology: Mycology

Question 1

How is Pneumocystis pneumonia diagnosed?

Answer 1

From a bronchoalveolar lavage or lung biopsy; sample stained with methenamine silver or identified with a fluorescent antibody

Question 2

A woman has a fungal infection that produces aflatoxins. For what condition should this patient periodically be monitored?

Answer 2

Hepatocellular carcinoma (Aflatoxins, produced by some Aspergillus species, are associated with this malignancy)

Question 3

How do you treat disseminated systemic mycoses?

Answer 3

Amphotericin B

Question 4

What region is blastomycosis endemic to?

Answer 4

Eastern or central United States, Great Lakes

Question 5

How is histoplasmosis generally acquired?

Answer 5

Inhalation from bird (eg, starling) or bat droppings

Question 6

How do Histoplasma, Blastomyces, Coccidioides, and Paracoccidioides organisms compare in terms of size to an RBC?

Answer 6

Histoplasma organisms are smaller; Blastomyces organisms are the same size; Coccidioides and Paracoccidioides organisms are larger

Question 7

A man with diabetes mellitus has a headache, facial pain, a black necrotic facial eschar, and cranial nerve palsies. What might cause his cranial nerve palsies?

Answer 7

Cavernous sinus thromboses, a possible complication of Mucor and Rhizopus infections

Question 8

How does Aspergillus fumigatus appear on culture media at 37°C?

Answer 8

45° branching septate hyphae with conidia radiating from the ends of conidiophores (broom-like appearance)

Question 9

A 70-year-old patient is diagnosed with coccidioidomycosis pneumonia subsequently develops persistent headache and blurry vision. What condition should he be evaluated for?

Answer 9

Meningitis; as coccidioidomycosis can result in meningitis

Question 10

How do you treat disseminated candidiasis?

Answer 10

Amphotericin B, fluconazole, or echinocandins

Question 11

What treatment options are available for Aspergillus infections?

Answer 11

Voriconazole, echinocandins (2nd line)

Question 12

Pathologically, how are systemic mycoses and tuberculosis similar?

Answer 12

Both can form granulomas

Question 13

An immunocompromised patient presents with “soap bubble” lesions in his brain on imaging. How does this infection most likely develop?

Answer 13

Cryptococcus neoformans spreads to the CNS (usually meninges) through hematogenous dissemination after inhalation

Question 14

A man has multiple erythematous scaling rings with central clearing. Where are these rings typically found?

Answer 14

On the torso; he likely has tinea corporis infection (ringworm)

Question 15

At what CD4+ count should patients who are HIV+ begin to receive prophylaxis against Pneumocystis pneumonia?

Answer 15

< 200 cells/mm3

Question 16

How do Mucor and Rhizopus proliferate in the body and cause infection?

Answer 16

The fungi grow in the blood vessels and enter the brain via the cribriform plate

Question 17

All systemic mycoses can primarily cause what type of illness?

Answer 17

Pneumonia; all can disseminate

Question 18

What class of organisms causes tinea pedis, cruris, corporis, capitis, and unguium?

Answer 18

Dermatophytes (representative geni include Microsporum, Trichophyton, Epidermophyton)

Question 19

Which group of hosts would be symptomatic if infected with Pneumocystis?

Answer 19

Immunocompromised patients (eg, those with AIDS); otherwise, most are asymptomatic

Question 20

A gardener presents with a pustule on her forearm and multiple nodules tracing upward toward her axilla. What is the most likely diagnosis?

Answer 20

Sporotrichosis (rose gardener’s disease)

Question 21

How do Mucor and Rhizopus enter the body?

Answer 21

Via inhalation of spores

Question 22

How is sporotrichosis treated?

Answer 22

Itraconazole or potassium iodide (for cutaneous/lymphocutaneous disease)

Question 23

An athlete has hypopigmented and hyperpigmented macules on her back after intensive summer training. What is the most likely diagnosis?

Answer 23

Tinea (pityriasis) versicolor (Malassezia spp, Pityrosporum spp)

Question 24

How are Mucor and Rhizopus infections with brain involvement treated?

Answer 24

Surgical debridement and amphotericin B or isavuconazole

Question 25

What populations are more likely to develop invasive aspergillosis?

Answer 25

Patients who are immunocompromised and those with disorders of neutrophil dysfunction (ie, chronic granulomatous disease)

Question 26

How does tinea versicolor cause discolored patches on skin?

Answer 26

Lipid degradation by Malassezia spp (Pityrosporum spp) produces acids→inhibit tyrosinase (melanin synthesis)→hypopigmentation; inflammatory responses→hyperpigmentation/pink patches

Question 27

Name 3 infections caused by Cryptococcus neoformans typically found in immunocompromised patients

Answer 27

Cryptococcosis, cryptococcal encephalitis, and cryptococcal meningitis

Question 28

What region is Coccidioidomycosis endemic to?

Answer 28

Southwestern United States and California

Question 29

What is the first-line treatment for oral thrush alone?

Answer 29

Treatment for superficial Candida infections is nystatin, fluconazole, or echinocandins

Question 30

What exposure is most strongly associated with coccidioidomycosis infection?

Answer 30

Dust exposure in endemic areas (eg, after earthquakes or during excavations)

Question 31

What fungal infection are patients with TB at risk for due to their cavitary lesions?

Answer 31

Aspergillus fumigatus, which may cause aspergillomas in preexisting lung cavities (especially those from TB)

Question 32

How is sporotrichosis transmitted?

Answer 32

Introduction of fungal spores into the skin after an injury, often caused by thorns (hence, rose gardener's disease)

Question 33

Paracoccidioidomycosis presents most similarly to which other systemic fungal disease?

Answer 33

Blastomycosis

Question 34

Which 2 groups of patients are most likely to develop ABPA (allergic bronchopulmonary aspergillosis)?

Answer 34

Patients with asthma and cystic fibrosis

Question 35

What is observed when the causative organism of diaper rash is grown at 37°C?

Answer 35

Germ tube formation at 37°C, which is diagnostic for Candida albicans

Question 36

What structure must Mucor and Rhizopus penetrate to invade the brain?

Answer 36

Cribriform plate

Question 37

How do TB and the systemic mycoses differ in transmission?

Answer 37

Only TB can be transmitted from person to person

Question 38

How is Coccidioides distinguished from all other dimorphic fungi?

Answer 38

It is a spherule in tissue (37°C), not a yeast

Question 39

What populations are at high risk for oral/esophageal thrush?

Answer 39

Immunocompromised: neonates, patients with diabetes and AIDS, chronic steroid users

Question 40

A 40-year-old immunocompromised man presents with pneumonia and verrucous skin lesions shortly after traveling to Wisconsin. What is the most likely diagnosis?

Answer 40

Blastomycosis

Question 41

How do you treat local infections of systemic mycoses?

Answer 41

With azoles (eg, itraconazole, fluconazole)

Question 42

What opportunistic fungus is a cause of endocarditis in IV drug users?

Answer 42

Candida albicans

Question 43

What part of the body is affected in a tinea unguium infection?

Answer 43

Nails (fungal nail infection is also termed onychomycosis)

Question 44

How do Mucor and Rhizopus spp. appear on culture media?

Answer 44

Broad, irregular, nonseptate hyphae that branch at wide angles

Question 45

What are the various prophylaxis options for Pneumocystis pneumonia?

Answer 45

Trimethoprim-sulfamethoxazole (TMP-SMX), dapsone, pentamidine, or atovaquone

Question 46

How does Pneumocystis pneumonia appear on methanamine-stained samples?

Answer 46

Disc-shaped yeasts

Question 47

Where is paracoccidioidomycosis endemic?

Answer 47

Latin America (Paracoccidioparasails with the captain’s wheel all the way to Latin America)

Question 48

You culture Cryptococcus neoformans at 25°C and then at 37°C. What morphology do you note?

Answer 48

C neoformans grows as a yeast at both temperatures (it is not dimorphic)

Question 49

What are the 3 different manifestations of tinea pedis?

Answer 49

Moccasin distribution, vesicular type, and interdigital (most common)

Question 50

Where is histoplasmosis endemic?

Answer 50

The Ohio and Mississippi River valleys

Question 51

What is the most specific test to confirm an infection with Cryptococcus neoformans?

Answer 51

Latex agglutination test to detect the polysaccharide capsular antigen

Question 52

A male patient, positive for HIV, has an infection with a heavily encapsulated, nondimorphic yeast. What stains are used to confirm the diagnosis?

Answer 52

India ink stain and mucicarmine; this is a Cryptococcus infection

Question 53

What is the appearance of Pneumocystis pneumonia on chest imaging?

Answer 53

Diffuse, bilateral ground-glass opacities with pneumatoceles

Question 54

What physical exam findings are evident in coccidioidomycosis?

Answer 54

Erythema nodosum (desert bumps) and multiforme arthralgias (desert rheumatism), may see meningeal signs if meningitis is present

Question 55

Where are the abscesses in Mucor and Rhizopus infections most commonly found?

Answer 55

Rhinocerebral and frontal lobes

Question 56

What do histoplasmosis, paracoccidioidomycosis, and blastomycosis have in common?

Answer 56

All are systemic mycoses caused by dimorphic fungi (metamorphosing into mold in cold [20°C] and into yeast in heat [37°C])

Question 57

Branching hyphae with rosettes of conidia grow on Sabouraud agar. How does this fungus appear when grown at 37°C?

Answer 57

Cigar-shaped buds (yeast phase); Sporothrix schenckii is dimorphic