Micro - Mycology Flashcards
Most fungal spores are _____ (sexual/asexual).
Asexual
Asexual fungal spores are also known as what?
Conidia
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?
Sporotrichosis (“rose gardener’s disease”) caused by Sporothrix schenckii;
treatment is itraconazole or potassium iodide
A girl has hyperpigmented skin patches. You biopsy the skin and see “spaghetti
and meatballs” on KOH prep. Diagnosis?
Tinea versicolor, caused by Malassezia furfur fungus
Name two systemic mycoses that are transmitted by inhalation of asexual spores.
Coccidioidomycosis and histoplasmosis
What do histoplasmosis, paracoccidioidomycosis, and blastomycosis have in
common?
They are all systemic mycoses caused by dimorphic fungi (mold in soil, but yeast in tissue (remember: mold = cold; heat = yeast)
Histoplasmosis is endemic in what area of the United States?
The Mississippi and Ohio River valleys
Histoplasmosis is most commonly transmitted via what substance?
Bird or bat droppings
Blastomycosis is endemic in what areas of the United States?
The states east of the Mississippi River; it is also common in Central America
What is the characteristic microscopic appearance of blastomycosis?
Big, broad-based budding
A 40-year-old male from Central America presents with dyspnea and
granulomatous skin nodules. What diagnosis do you expect?
Blastomycosis
Coccidioidomycosis is endemic in what area of the United States?
The southwestern United States, including California
What are two colloquial names for disease caused by coccidioidomycosis?
San Joaquin Valley fever and desert valley fever (desert bumps)
Paracoccidioidomycosis is endemic in what area?
Latin America
The yeast that causes paracoccidioidomycosis has what appearance on
microscopy?
The “captains wheel” appearance
What is the treatment of choice for local infection with dimorphic fungi?
Fluconazole or ketoconazole
What is the treatment of choice for systemic infection with dimorphic fungi?
Amphotericin B
Systemic mycoses can mimic which other infectious disease with granuloma
formation?
Tuberculosis
Histoplasmosis has what appearance under microscopy?
Macrophages filled with yeast (remember: Histo Hides in macrophages)
All systemic mycoses can cause what type of illness?
Pneumonia that can disseminate
In addition to pneumonia, what other illnesses can coccidioidomycosis cause?
Meningitis with dissemination to skin and bone
Describe the sizes of the four dimorphic fungi in relation to the size of a red blood
cell.
Histoplasmosis: smaller; blastomycosis: same; coccidioidomycosis and
paracoccidioidomycosis: larger
Tinea versicolor is caused by what organism?
Malassezia furfur
An athlete presents with hypopigmented macules on her upper back after a summer
of exercising. What is your diagnosis and what is the treatment?
Tinea versicolor; treat with topical miconazole and selenium sulfide
What are the characteristic skin lesions of tinea pedis, cruris, corporis, and capitis?
Pruritic lesions with central clearing that resembles a ring (the infection is
colloquially known as ringworm)
Tinea pedis, tinea cruris, tinea corporis, and tinea capitis are caused by what
organisms?
Dermatophytes (ie, Microsporum, Trichophyton, Epidermophyton)
What animals are commonly reservoirs for Microsporum?
House pets
What is the typical microscopic appearance of the agent causing tinea versicolor on
KOH prep?
“Spaghetti and meatballs” (Malassezia furfur)
Pets infected with Microsporum can be treated with what?
Topical azoles
What causes hypopigmented patches of tinea versicolor?
Degradation of lipids by Malassezia furfur, producing acids that damage
melanocytes
Dermatophytes have what microscopic appearance in KOH prep?
Visible mold hyphae
What four patient populations commonly contract oral and esophageal thrush as a
result of Candida infection?
Neonates, steroid users, patients with diabetes, and patients with AIDS
How is Candida albicans diagnosed microscopically?
Yeast with pseudohyphae in culture, germ tubes at body temperature
Vulvovaginitis caused by Candida albicans commonly occurs in what types of
patients?
Women with a high vaginal pH, diabetes, and/or a recent history of antibiotic use
What three diseases are caused by Aspergillus fumigatus?
Allergic bronchopulmonary aspergillosis, lung cavity aspergilloma (“fungus ball”),
and invasive aspergillosis
Aspergillus fumigatus is a ____ (mold/yeast/dimorphic) with a _____ branching
pattern and ____ hyphae.
Mold (not dimorphic); V-shaped (remember: Acute Angles in Aspergillus); septate
Cryptococcus neoformanscauses what two diseases?
Cryptococcosis and cryptococcal meningitis
Which two tests can be used to diagnose cryptococcal infection?
India ink stain and latex agglutination test
Where can the heavily encapsulated yeast of Cryptococcus neoformans be found in
nature?
Soil and pigeon droppings
On what medium is Cryptococcus neoformanscultured?
Sabouraud’s agar
What stain can be used to visualize Cryptococcus neoformans?
India Ink
How are Mucorand Rhizopus species morphologically different
from Aspergillus species?
Mucor and Rhizopus have irregular, nonseptate hyphae with wide-angle branching,
while Aspergillus have more uniform septate hyphae with acute-angle branching
A patient exposed to bat droppings develops pneumonia. You see macrophages
filled with yeast on microscopy. Diagnosis?
Histoplasmosis
A pigeon keeper on immunosuppressants develops meningitis. You sample
the cerebrospinal fluid and see heavily encapsulated yeast. Diagnosis?
Cryptococcus neoformans infection
