Micro - Mycology

Question 1

Most fungal spores are _____ (sexual/asexual).

Answer 1

Asexual

Question 2

Asexual fungal spores are also known as what?

Answer 2

Conidia

Question 3

A gardener has an arm pustule with ascending lymphangitis. You biopsy it and see a fungus. What is it and how do you treat it?

Answer 3

Sporotrichosis (“rose gardener’s disease”) caused by Sporothrix schenckii; treatment is itraconazole or potassium iodide

Question 4

A girl has hyperpigmented skin patches. You biopsy the skin and see “spaghetti and meatballs” on KOH prep. Diagnosis?

Answer 4

Tinea versicolor, caused by Malassezia furfur fungus

Question 5

Name two systemic mycoses that are transmitted by inhalation of asexual spores.

Answer 5

Coccidioidomycosis and histoplasmosis

Question 6

You see this fungus in the cerebrospinal fluid of an HIV-positive man with meningitis. What is it?

Answer 6

Candida albicans, yeasts with wide capsular halos that exhibit narrow-based budding

Question 7

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

Answer 7

They are all systemic mycoses caused by dimorphic fungi (mold in soil, but yeast in tissue (remember: mold = cold; heat = yeast)

Question 8

Histoplasmosis is endemic in what area of the United States?

Answer 8

The Mississippi and Ohio River valleys

Question 9

Histoplasmosis is most commonly transmitted via what substance?

Answer 9

Bird or bat droppings

Question 10

Blastomycosis is endemic in what areas of the United States?

Answer 10

The states east of the Mississippi River; it is also common in Central America

Question 11

What is the characteristic microscopic appearance of blastomycosis?

Answer 11

Big, broad-based budding

Question 12

A 40-year-old male from Central America presents with dyspnea and granulomatous skin nodules. What diagnosis do you expect?

Answer 12

Blastomycosis

Question 13

Coccidioidomycosis is endemic in what area of the United States?

Answer 13

The southwestern United States, including California

Question 14

What microscopic appearance distinguishes coccidioidomycosis from all other dimorphic fungi?

Answer 14

It is a spherule in tissue, not a yeast

Question 15

What are two colloquial names for disease caused by coccidioidomycosis?

Answer 15

San Joaquin Valley fever and desert valley fever (desert bumps)

Question 16

Paracoccidioidomycosis is endemic in what area?

Answer 16

Latin America

Question 17

The yeast that causes paracoccidioidomycosis has what appearance on microscopy?

Answer 17

The “captains wheel” appearance

Question 18

What is the treatment of choice for local infection with dimorphic fungi?

Answer 18

Fluconazole or ketoconazole

Question 19

What is the treatment of choice for systemic infection with dimorphic fungi?

Answer 19

Amphotericin B

Question 20

Systemic mycoses can mimic which other infectious disease with granuloma formation?

Answer 20

Tuberculosis

Question 21

Histoplasmosis has what appearance under microscopy?

Answer 21

Macrophages filled with yeast (remember: Histo Hides in macrophages)

Question 22

All systemic mycoses can cause what type of illness?

Answer 22

Pneumonia that can disseminate

Question 23

In addition to pneumonia, what other illnesses can coccidioidomycosis cause?

Answer 23

Meningitis with dissemination to skin and bone

Question 24

Describe the sizes of the four dimorphic fungi in relation to the size of a red blood cell.

Answer 24

Histoplasmosis: smaller; blastomycosis: same; coccidioidomycosis and paracoccidioidomycosis: larger

Question 25

Tinea versicolor is caused by what organism?

Answer 25

*Malassezia furfur*

Question 26

An athlete presents with hypopigmented macules on her upper back after a summer of exercising. What is your diagnosis and what is the treatment?

Answer 26

Tinea versicolor; treat with topical miconazole and selenium sulfide

Question 27

What are the characteristic skin lesions of tinea pedis, cruris, corporis, and capitis?

Answer 27

Pruritic lesions with central clearing that resembles a ring (the infection is colloquially known as ringworm)

Question 28

Tinea pedis, tinea cruris, tinea corporis, and tinea capitis are caused by what organisms?

Answer 28

Dermatophytes (ie, *Microsporum, Trichophyton, Epidermophyton*)

Question 29

What animals are commonly reservoirs for *Microsporum*?

Answer 29

House pets

Question 30

What is the typical microscopic appearance of the agent causing tinea versicolor on KOH prep?

Answer 30

"Spaghetti and meatballs" (*Malassezia furfur*)

Question 31

Pets infected with *Microsporum* can be treated with what?

Answer 31

Topical azoles

Question 32

What causes hypopigmented patches of tinea versicolor?

Answer 32

Degradation of lipids by *Malassezia furfur*, producing acids that damage melanocytes

Question 33

Dermatophytes have what microscopic appearance in KOH prep?

Answer 33

Visible mold hyphae

Question 34

What four patient populations commonly contract oral and esophageal thrush as a result of *Candida* infection?

Answer 34

Neonates, steroid users, patients with diabetes, and patients with AIDS

Question 35

How is *Candida albicans* diagnosed microscopically?

Answer 35

Yeast with pseudohyphae in culture, germ tubes at body temperature

Question 36

Vulvovaginitis caused by *Candida albicans* commonly occurs in what types of patients?

Answer 36

Women with a high vaginal pH, diabetes, and/or a recent history of antibiotic use

Question 37

What three diseases are caused by *Aspergillus fumigatus*?

Answer 37

Allergic bronchopulmonary aspergillosis, lung cavity aspergilloma ("fungus ball"), and invasive aspergillosis

Question 38

*Aspergillus fumigatus* is a ____ (mold/yeast/dimorphic) with a _____ branching pattern and ____ hyphae.

Answer 38

Mold (not dimorphic); V-shaped (remember: **A**cute **A**ngles in **A**spergillus); septate

Question 39

*Cryptococcus neoformans* causes what two diseases?

Answer 39

Cryptococcosis and cryptococcal meningitis

Question 40

Which two tests can be used to diagnose cryptococcal infection?

Answer 40

India ink stain and latex agglutination test

Question 41

Where can the heavily encapsulated yeast of *Cryptococcus neoformans* be found in nature?

Answer 41

Soil and pigeon droppings

Question 42

On what medium is *Cryptococcus neoformans* cultured?

Answer 42

Sabouraud’s agar

Question 43

What stain can be used to visualize *Cryptococcus neoformans*?

Answer 43

India Ink

Question 44

How are *Mucor* and *Rhizopus* species morphologically different from *Aspergillus* species?

Answer 44

*Mucor* and *Rhizopus* have irregular, nonseptate hyphae with wide-angle branching, while *Aspergillus* have more uniform septate hyphae with acute-angle branching

Question 45

This image shows the characteristic microscopic appearance of which fungus?

Answer 45

Blastomycosis with big, broad-based budding (**B**lasto **B**uds **B**roadly)

Question 46

The yeast that has a "captain's wheel" appearance causes what systemic mycosis?

Answer 46

Paracoccidioidomycosis

Question 47

A patient exposed to bat droppings develops pneumonia. You see macrophages filled with yeast on microscopy. Diagnosis?

Answer 47

Histoplasmosis

Question 48

A pigeon keeper on immunosuppressants develops meningitis. You sample the cerebrospinal fluid and see heavily encapsulated yeast. Diagnosis?

Answer 48

*Cryptococcus neoformans* infection