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USMLE (S1) Microbiology > Micro - Mycology > Flashcards

Flashcards in Micro - Mycology Deck (48)
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1
Q

Most fungal spores are _____ (sexual/asexual).

A

Asexual

2
Q

Asexual fungal spores are also known as what?

A

Conidia

3
Q

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?

A

Sporotrichosis ("rose gardener's disease") caused by Sporothrix schenckii; treatment is itraconazole or potassium iodide

4
Q

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

A

Tinea versicolor, caused by Malassezia furfur fungus

5
Q

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

A

Coccidioidomycosis and histoplasmosis

6
Q

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

A

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

7
Q

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

A

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

8
Q

Histoplasmosis is endemic in what area of the United States?

A

The Mississippi and Ohio River valleys

9
Q

Histoplasmosis is most commonly transmitted via what substance?

A

Bird or bat droppings

10
Q

Blastomycosis is endemic in what areas of the United States?

A

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

11
Q

What is the characteristic microscopic appearance of blastomycosis?

A

Big, broad-based budding

12
Q

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

A

Blastomycosis

13
Q

Coccidioidomycosis is endemic in what area of the United States?

A

The southwestern United States, including California

14
Q

What microscopic appearance distinguishes coccidioidomycosis from all other dimorphic fungi?

A

It is a spherule in tissue, not a yeast

15
Q

What are two colloquial names for disease caused by coccidioidomycosis?

A

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

16
Q

Paracoccidioidomycosis is endemic in what area?

A

Latin America

17
Q

The yeast that causes paracoccidioidomycosis has what appearance on microscopy?

A

The "captains wheel" appearance

18
Q

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

A

Fluconazole or ketoconazole

19
Q

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

A

Amphotericin B

20
Q

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

A

Tuberculosis

21
Q

Histoplasmosis has what appearance under microscopy?

A

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

22
Q

All systemic mycoses can cause what type of illness?

A

Pneumonia that can disseminate

23
Q

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

A

Meningitis with dissemination to skin and bone

24
Q

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

A

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

25
Q

Tinea versicolor is caused by what organism?

A

Malassezia furfur

26
Q

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

A

Tinea versicolor; treat with topical miconazole and selenium sulfide

27
Q

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

A

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

28
Q

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

A

Dermatophytes (ie, Microsporum, Trichophyton, Epidermophyton)

29
Q

What animals are commonly reservoirs for Microsporum?

A

House pets

30
Q

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

A

"Spaghetti and meatballs" (Malassezia furfur)

31
Q

Pets infected with Microsporum can be treated with what?

A

Topical azoles

32
Q

What causes hypopigmented patches of tinea versicolor?

A

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

33
Q

Dermatophytes have what microscopic appearance in KOH prep?

A

Visible mold hyphae

34
Q

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

A

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

35
Q

How is Candida albicans diagnosed microscopically?

A

Yeast with pseudohyphae in culture, germ tubes at body temperature

36
Q

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

A

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

37
Q

What three diseases are caused by Aspergillus fumigatus?

A

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

38
Q

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

A

Mold (not dimorphic); V-shaped (remember: Acute Angles in Aspergillus); septate

39
Q

Cryptococcus neoformans causes what two diseases?

A

Cryptococcosis and cryptococcal meningitis

40
Q

Which two tests can be used to diagnose cryptococcal infection?

A

India ink stain and latex agglutination test

41
Q

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

A

Soil and pigeon droppings

42
Q

On what medium is Cryptococcus neoformans cultured?

A

Sabouraud’s agar

43
Q

What stain can be used to visualize Cryptococcus neoformans?

A

India Ink

44
Q

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

A

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

45
Q

This image shows the characteristic microscopic appearance of which fungus?

A

Blastomycosis with big, broad-based budding (Blasto Buds Broadly)

46
Q

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

A

Paracoccidioidomycosis

47
Q

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

A

Histoplasmosis

48
Q

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

A

Cryptococcus neoformans infection