Microbiology Mycology - First Aid

Question 1

Systemic mycoses can all cause…

Answer 1

pneumonia and can disseminate.

Question 2

All systemic mycoses are caused by…

Answer 2

dimorphic fungi:

• cold (20 C) = mold
• heat (37 C) = yeast

*The only exception is coccidioidomycosis which is a spherule (not yeast) in tissue.

Question 3

Treatment for Systemic Mycoses

Answer 3

Local infection: Fluconazole or Itracoazole

Systemic infection: Amphotericin B

Question 4

Systemic mycoses can mimic…

Answer 4

TB (w/ granuloma formation) but unlike TB, they have no person-to-person transmission.

Question 5

Systemic mycoses types (4)

Answer 5

1. Histoplasmosis
2. Blastomycosis
3. Coccidioidomycosis
4. Paracoccidioidomycosis

Question 6

Histoplamosis features (4)

Answer 6

• Mississippi and Ohio River valleys
• causes pneumonia
• macrophages filled with histo
• bird or bat droppings

Question 7

Blastomycosis features (4)

Answer 7

• states east of Mississippi river (and Central America)
• causes inflammatory lung disease and can disseminate to bone and skin
• forms granulomatous nodules
• broad-base budding

Question 8

Coccidioidomycosis features (6)

Answer 8

• Southwest US
• causes pneumonia and meningitis
• can disseminate to skin and bone
• spherule filled with endospores
• erythema nodosum (desert bumps)
• arthralgias (desert rheumatism)

Question 9

Coccidioidomycosis rates increase after…

Answer 9

earthquakes which causes spores in the dust to be thrown up into the air.

Question 10

Paracoccidioidomycosis features (2)

Answer 10

• Latin America

- budding yeast w/ “captain’s wheel” formation

Question 11

Tinea versicolor is caused by…

Answer 11

Malassezia furfur which degrades lipids producing acids that damage melanocytes and cause hypopigmented/hyperpigmented patches.

Question 12

Tinea versicolor occurs in…

Answer 12

hot, humid weather.

Has a “spaghetti and meatball” appearance.

Question 13

Treatment for tinea versicolor

Answer 13

topical miconazole, selenium sulfide

Question 14

Other tineae (cutaneous mycoses) include…

Answer 14

tinea pedis (foot)
tinea cruris (groin)
tinea corporis (ringworm, on body)
tinea capitis (head, scalp)
tinea unguium (onychomycosis on nails)

Question 15

Dermatophytes include (3):

Answer 15

1. Microsporum
2. Trichophyton
3. Epidermophyton

Question 16

Dermatophytes cause..

Answer 16

pruritic lesions with central clearing resembling a ring.

Question 17

In a KOH prep, dermatophytes show as…

Answer 17

mold hyphae, not dimorphic.

Question 18

Opportunistic fungal infections (6)

Answer 18

1. Candida albicans
2. Aspergillus fumigatus
3. Cryptococus neoformans
4. Mucor and Rhizopus
5. Pneumocystis jirovecii
6. Sporothrix schenckii

Question 19

Candida albicans causes:

Answer 19

• oral and esophageal thrush
• vulvovaginitis
• diaper rash
• endocarditis in IV drug users
• mucocutaneous candidiasis

Question 20

Treatment for Candida albicans

Answer 20

Vaginal - topical azole
Oral/esophageal - fluconzaole, caspofungin
Systemic - fluconazole, Amphotericin B, Caspofungin

Question 21

Aspergillus fumigatus casues…

Answer 21

Allergic Bronchopulmonary Aspergillosis: associated with asthma and CF; may cause bronchiectasis and eosinophilia

Aspergillomas in lung cavities, esp after TB.

Question 22

Some species of Aspergillus produce…

Answer 22

aflatoxins which are associated with hepatocellualr carcinoma.

Question 23

Candida albicans features (3)

Answer 23

• dimorphic yeast
• pseudohyphae and budding yeasts at 20 C
• germ tubes at 37 C

Question 24

Aspergillus fumigatus features (4)

Answer 24

• invasive esp in those with chronic granulomatous disease
• septate hyphae that branch at acute (45 degree) angles
• conidiophore with radiating chains of spores
• not dimorphic

Question 25

Cryptococcus neoformans causes…

Answer 25

cryptococcal meningitis (soap bubble lesions in the brain) and cryptococcosis.

Question 26

Cryptococcus neoformans features

Answer 26

• heavily encapsulated yeast
• not dimorphic
• soil, pigeon droppings
• wide capsular halos and unequal budding

Question 27

Cryptococcuus neoformans is acquired through…

Answer 27

inhalation with hematogenous dissemination to the meninges.

Question 28

The most specific test for cryptococcus neoformans is…

Answer 28

latex agglutination test which detects polysaccharide capsular antigen.

Question 29

Mucor and Rhizopus cause…

Answer 29

mucormycosis mostly in ketoacidotic diabetic and leukemic pts.

Question 30

Mucor and Rhizopus fungi proliferate in…

Answer 30

blood vessel walls when there is excess ketone and glucose, penetrate the cribiform plate and enter the brain. This causes rhinocerebral, frontal lobe abcesses.

Question 31

Signs of Mucor and Rhizopus infection

Answer 31

• HA
• facial pain
• black necrotic eschar on face
• cranial nerve involvement

Question 32

Treatment for Mucor and Rhizpus

Answer 32

Amphotericin B

Question 33

Mucor appearance

Answer 33

irregular, broad, nonseptate hyphae branching at wide angles

Question 34

Pneumocystis jirovecii causes…

Answer 34

pneumocystis pneumonia, a diffuse interstitial pneumonia.

Question 35

Pneumocystis jirovecii features

Answer 35

• inhaled
• usually asymptomatic
• disc-shaped yeast forms on methenamine silver stain of lung tissue

Question 36

Treatment/prophylaxis for pneumocystis jirovecii

Answer 36

TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only)

Question 37

Start prophylaxis for pneumocystits when…

Answer 37

CD4 count drops to less than 200 in HIV pts.

Question 38

Sporothrix schenckii causes…

Answer 38

sporotrichosis. When spores are traumatically introduced into the skin, typically by a thorn (rose gardener’s disease), it causes a pustule/ulcer with nodules along draining lymphatics.

Question 39

Sporothrix schenckii features (3)

Answer 39

• dimorphic
• cigar-shaped budding yeast
• lives on vegetation

Question 40

Treatment for Sporothrix schenckii

Answer 40

Itraconazole or Potassium iodide