Microbiology - Mycology

Front 1

What are the common characteristics of Systemic Mycoses?

Back 1

- All can cause pneumonia and disseminate
- All caused by dimorphic fungi - cold (20°C) = mold; heat (37°C) = yeast (exception: cocci is a spherule not yeast in tissue)
- Treat local infection with fluconazole or itraconazole
- Treat systemic infection with amphotericin B
- Systemic mycoses can mimic TB (granuloma formation) but there is no person-to-person transmission

Front 2

How do Systemic Mycoses compare to TB?

Back 2

- Both have granuloma formation
- Mycoses do not have person-to-person transmission

Front 3

What are the systemic mycoses?

Back 3

- Histoplasmosis
- Blastomycosis
- Coccidioidomycosis
- Paracoccidioidomycosis

Front 4

Which mycoses is endemic to the Mississippi and Ohio River valleys? What does it cause? Pathologic features?

Back 4

Histoplasmosis
- Causes pneumonia
- Macrophages filled with histoplasma (smaller than RBCs) - "Histo Hides (within macrophages)"
- Associated with bird and bat droppings

Front 5

Which mycoses is endemic to the states east of the Mississippi River and Central America? What does it cause? Pathologic features?

Back 5

Blastomycosis
- Causes inflammatory lung disease and can disseminate to skin and bone
- Forms granulomatous nodules
- Blasto Buds Broadly (same size as RBCs)

Front 6

Which mycoses is endemic to the SW US and California? What does it cause? Pathologic features?

Back 6

Coccidioidomycosis
- Causes pneumonia and meningitis
- Can disseminate to skin ("desert bumps" = erythema nodosum) and bone ("desert rheumatism" = arthrlagias)
- Case rate increases after earthquakes (spores in dust are thrown up in the air and become spherules in lungs)
- Spherule (much larger than RBCs) filled with endospores - "Coccidio Crowds"

Front 7

Which mycoses is endemic to Latin America? What does it cause? Pathologic features?

Back 7

Paracoccidioidomycosis
- Budding yeast with "Captain's Wheel" formation (much larger than RBCs
- "Paracoccidio parasails with the captain's wheel all the way to Latin America"

Front 8

What is the relative size of the systemic mycoses to RBCs?

Back 8

- Histoplasmosis: smaller than RBC
- Blastomycosis: same size as RBC
- Coccidioidomycosis: much larger than RBC
- Paracoccidioidomycosis: much larger than RBC

Front 9

What is the location in which the systemic mycoses are endemic?

Back 9

- Histoplasmosis: Mississippi and Ohio River valleys
- Blastomycosis: states east of Mississippi River and Central America
- Coccidioidomycosis: SW US, California
- Paracoccidioidomycosis: Latin America

Front 10

What are the cutaneous mycoses?

Back 10

- Tinea versicolor
- Other Tinea: pedis (foot), cruris (groin), corporis (ringworm on body), capitis (head/scalp), unguium (onychomycosis - on fingernails)

Front 11

What is the cause of Tinea Versicolor? When is it more common?

Back 11

Malassezia Furfur - "spaghetti and meatball" appearance
- More common in hot, humid weather

Front 12

What does Malassezia Furfur cause?

Back 12

- Degradation of lipids produces acids that damage melanocytes
- Causes hypopigmented and/or hyperpigmented patches
- Causes Tinea Versicolor

Front 13

How do you treat Tinea Versicolor (Malassezia Furfur)?

Back 13

Topical miconazole, selenium sulfide (Selsun)

Front 14

What causes the other Tineae (eg, pedis, cruris, corporis, capitis, unguium)? Types of lesions?

Back 14

- Caused by Dermatophytes (Microsporum, Trichophyton, and Epidermophyton)
- Pruritic lesions with central clearing that resembles a ring

Front 15

What are the Dermatophytes that cause Tineae? Appearance?

Back 15

- Microsporum
- Trichophyton
- Epidermophyton

See mold hyphae in KOH prep but not dimorphic

Front 16

What are the opportunistic fungal infections?

Back 16

- Candida albicans
- Aspergillus fumigatus
- Cryptococcus neoformans
- Mucor and Rhizopus species
- Pneumocystis jirovecii
- Sporothrix schenckii

Front 17

Which fungus causes oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDS), vulvovaginitis (diabetes, use of antibiotics), diaper rash, endocarditis in IV drug users, disseminated infection (to any organ), and chronic mucocutaneous infection?

Back 17

Candida albicans (alba = white)

Front 18

What forms does Candida albicans have?

Back 18

Dimorphic yeast
- Pseudohyphae and budding yeasts at 20°C
- Germ tubes at 37°C

Front 19

What kind of Candida albicans infection occurs in patients who are immunocompromised (neonates, steroids, diabetes, AIDS)? Treatment?

Back 19

Oral and esophageal thrush - treat with fluconazole or caspofungin

Front 20

What kind of Candida albicans infection occurs in patients who have diabetes or are using antibiotics? Treatment?

Back 20

Vulvovaginitis - treat with topical azole

Front 21

What kind of Candida albicans infection occurs in infants?

Back 21

Diaper rash

Front 22

What kind of Candida albicans infection occurs in patients who are IV drug users?

Back 22

Endocarditis

Front 23

How do you treat systemic Candida albicans infections?

Back 23

Fluconazole, Amphotericin B, OR Caspofungin

Front 24

Which fungus can cause invasive infection, allergic bronchopulmonary infection, and masses of fungus in lung cavities?

Back 24

Aspergillus fumigatus

Front 25

Characteristics of Aspergillus fumigatus? Appearance?

Back 25

- Septate hyphae branch at 45° angle ("think A for Acute Angles in Aspergillus")
- Not dimorphic
- Conidiophore with radiating chains of spores

Front 26

Who is most likely to get invasive Aspergillus fumigatus infection?

Back 26

Immunocompromised and those with chronic granulomatous disease

Front 27

Which form of Aspergillus fumigatus infection is associated with asthma and cystic fibrosis? What can it cause?

Back 27

Allergic Bronchopulmonary Aspergillosis (ABPA)
- May cause bronchiectasis and eosinophilia

Front 28

What form of Aspergillus fumigatus infection is more common after TB infection?

Back 28

Aspergillomas in lung cavities

Front 29

What can some species of Aspergillus fumigatus produce? Implications?

Back 29

Some species produce AFLATOXINS which are associated with Hepatocellular Carcinoma

Front 30

Which fungus is found in soil and pigeon droppings and can cause meningitis?

Back 30

Cryptococcus neoformans

Front 31

Characteristics of Cryptococcus neoformans?

Back 31

- Heavily encapsulated yeast with unequal budding
- Not dimorphic
- Culture on Sabouraud agar
- Stains with India ink (picture) and mucicarmine
- Latex agglutination test detects polysaccharide capsular antigen and is more specific

Front 32

What disease is caused by Cryptococcus neoformans infection? How is it acquired?

Back 32

- Cryptococcal meningitis
- Cryptococcosis

- Acquired through inhalation of fungus found in soil and pigeon droppings
- Hematogenous dissemination to meninges

Front 33

Which fungus causes "soap bubble" lesions in the brain?

Back 33

Cryptococcus neoformans

Front 34

Which fungus causes disease mainly in ketoacidotic diabetic and leukemic patients?

Back 34

Mucor and Rhizopus species → Mucormycosis

Front 35

What is the pathogenesis of Mucor and Rhizopus species?

Back 35

- Fungi proliferate in blood vessel walls when there is excess ketone and glucose
- Penetrates cribiform plate
- Enters brain → rhinocerebral and frontal lobe abscesses

Front 36

What are the symptoms of infection by Mucor and Rhizopus species?

Back 36

- Headache
- Facial pain
- Black necrotic eschar on face
- May have cranial nerve involvement
(due to abscesses in rhinocerebral, frontal lobes)

Front 37

How do you treat Mucor and Rhizopus species infections?

Back 37

Amphotericin B

Front 38

What is the appearance of Mucor species?

Back 38

Irregular, broad, non-septate hyphae branching at wide angles

Front 39

Which fungus is usually asymptomatic but in immunosuppressed (eg, AIDS) causes a diffuse interstitial pneumonia?

Back 39

Pneumocystis jirovecii

Front 40

Who is affected by Pneumocystis jirovecii infection? How?

Back 40

- Inhaled
- Most infections are asymptomatic
- Infection in immunosuppressed patients (eg, AIDS) predisposes to disease → Pneumocystis pneumonia (PCP)
- PCP is a diffuse interstitial pneumonia

Front 41

What are the characteristics of Pneumocystis pneumonia (PCP)? Diagnosis?

Back 41

- Diffuse interstitial pneumonia
- Diffuse, bilateral CXR appearance
- Diagnosed by lung biopsy or lavage
- Disc-shaped yeast forms on methenamine silver stain of lung tissue

Front 42

What is the appearance of Pneumocystis jirovecii?

Back 42

Yeast:
- Disc-shaped yeast forms on methenamine silver stain of lung tissue

Front 43

How do you treat a Pneumocystis jirovecii infection?

Back 43

- TMP-SMX
- Pentamidine

Front 44

When should you do prophylactic treatment for Pneumocystis jirovecii? Regimen?

Back 44

- Start prophylaxis when CD4 counts drop <200 cells/mm3 in HIV patients
- Use Dapsone, Atovaquone, TMP-SMX, and Pentamidine

Front 45

Which fungus typically presents in gardeners and causes a local pustule or ulcer with nodules along draining lymphatic (ascending lymphangitis)

Back 45

Sporothrix schenckii

Front 46

What is the appearance and location of Sporothrix schenckii?

Back 46

Dimorphic, cigar-shaped budding yeast that lives on vegetation

Front 47

How do you get infected with Sporothrix schenckii? Disease?

Back 47

- Spores are usually traumatically introduced into the skin, typically by a thorn ("rose gardener's disease")
- Causes Sporotrichosis → local pustule or ulcer with nodules along the draining lymphatics (ascending lymphangitis)
- Little systemic illness

Front 48

How do you treat Sporothrix schenckii?

Back 48

Itraconazole or POTassium iodide
(remember it is typically in rose gardener's - "plant a rose in the POT")