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STEP 1 (4) > Mycology > Flashcards

Mycology Flashcards

1
Q

What fungi can cause systemic mycoses?

A

Histoplasmosis

Blastomycosis

Coccidioidomycosis

Paracoccidioidomycosis

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2
Q

Notes about the systemic mycoses inducing fungi

A
  • All can cause pneumonia and can disseminate
  • All are dimorphic fungi (cold (20C)= mold; heat (37C)= yeast)- the only exception is coccoidomycosis, which is a spherule (not yeast) in tissue

Tx with fluconazole or itra for local infection and ampho B for systemic

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3
Q

Systemic mycoses can mimic TB (granuloma formation) but…

A

they have no person-person transmission

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4
Q

What is this?

A

Histoplasmosis (histo bodies within macrophages)- associated with brid or bat droppings

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5
Q

Where is Histoplasmosis endemic?

A

Mississippi and Ohio River Valleys- causes pneumonia

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6
Q

Blastomycosis-broad-based buding (same size as RBCs)

A

Blastomycosis- causes inflammatory lung disease and can disseminate to skin and bone (forms granulomatous nodules)

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7
Q

Blastomycosis- common in states east of the Mississippi River and Central America

A
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8
Q

Coccidioidomycosis- spherules (much larger than RBCs)- filled with endospores

A

Coccidioidomycosis

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9
Q

Where is Coccidioidomycosis common?

A

Southwestern US, California- causes meningitis and penumonia and can disseminate to bone and skin

Common after earthquakes when spores are thrown into the air and inhaled to form spherules

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10
Q

Paracoccidioidoycosis- budding yeast with ‘captains wheel’ formation

A

Paracoccidioidoycosis-common in Latin America

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11
Q

What are the major cutaneous mycoses?

A

TInea (dermatophytes)- capitis, corporis, cruris, pedis, unguium

Tinea versicolor

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12
Q

Dermatophytes (tinea) include what spp?

A

Microsporum

Trichophyton

Epidermophyton

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13
Q

How is Tinea diagnosed?

A

branching septate hyphae visible on KOH prep with blue fungal stain

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14
Q

How does tinea capitis present?

A

Occurs on head, scalp, and is associated with LD< alopcia, and scaling

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15
Q

How does tinea corporis present?

A

Occurs on the body and is marked by erythematous scaling rings (ringworm) and central clearing- can be acquired from contact with an infected dog or cat

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16
Q

How does tinea cruris present?

A

Occurs in inguinal area and often DOES NOT show the central clearing seen in tinea corporis

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17
Q

Describe tinea pedia

A

3 varieties:

Interdigital (most common) (below)

Moccasin distribution

Vesicular types

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18
Q

Tinea pedis- Vesicular type

A

Tinea pedis- Moccasin type

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19
Q

Describe Tinea unguium

A

Onchomycosis; occurs on nails

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20
Q

What causes Tinea versicolor?

A

Malassezia spp (Pityrosporum spp.), a yeast-like fungus (not a dermatophyte despite being called tinea)

NOTE: Below: degradation of lipids produces acids that daage melanocytes and cause hypopigmentation and/or pink patches

21
Q

When is Tinea versicolor most common?

A

summer (hot, humid weather)

22
Q

What does Tinea versicolor look like on microscopy?

A

Spaghetti and meatballs

23
Q

What are the main opportunistic fungal infections?

A

Candida albicans

Aspergillus fumigatus

Crytpococcus neoformans

Mucor and Rhizopus spp.

24
Q

What is this?

A

Candida albicans- pseudohyphae and budding yeasts at 20C and germ tubes at 37C

25
Q

Candida can cause oral and esophageal thrush in immunocompromised (neonates, steroids, diabetes, AIDs), vulvoganitis (diabets, ABX users), diaper rash, endocarditis in IVDU, disseminated candidiasis

A

Candida vulvovaginitis

26
Q

How is Candida tx?

A

topical axzole for vaginal

nystatin, fluconazole, or caspofungin for oral/esophagel

fluconazole, caspofungin, or ampho B for systemic

27
Q

Aspergillus fumigatus- invasive aspergillosis, especially in immunocompromised and those with chronic granulomatous disease

Diagnosis: Septate hyphae that branch at 45 degrees (ACUTE!!)

A

NOT dimorphic

28
Q

What diseases does Aspergillus fumigatus cause?

A

Alergic bronchopulmonary aspergillosis (ABPA)- associated with asthma and cystic fibrosis; may cause bronchiectasis and eosinophilia

Aspergillomas in lung cavities, especially after TB infection

29
Q

Some species of Aspergillus produce _______

A

alfatoxins, which are associated with hepatocellular carcinoma

30
Q

What is this?

A

Cryptococcus neoformans, the cause of cryptococcosis

31
Q

What is the structure of Cryptococcus neoformans?

A

heavily encapsulated yeast (not dimorphic)

32
Q

What is the major association of Cryptococcus neoformans?

A

soil and pigeon droppings (acquired through inhalation with heme dissemination to meninges)

33
Q

How is Cryptococcus neoformans confirmed?

A

India Ink or mucicarmine stain

culture on Saboruaud agar

Latex agglutination test detects polysaccharide capsular antigen and is more specific

34
Q

Crypto- soap bubble lesion in brains

A

Crypto- soap bubble lesion in brains

35
Q

What fungal disease is most common in ketoacidotic diabetics and/or neutropenic pts (e.g. leukemia)?

A

Mucormycosis

36
Q

Mucomycosis- look for rhinocerebeal, frontal lobe abscesses, or cavernous sinus thrombosis

HA, facial pain, and black necrotic eschars on face common

A

Wide angle branching hyphae!!

37
Q

How is Mucormycosis tx?

A

surgical debridement and ampho B

38
Q

What is the cause of Pneumocystis pneumonia (PCP)?

A

Pneumocystis jirovecii

39
Q

Describe Pneumocystis jirovecii

A

This is a yeast like fungus that is inhaled and most infections are asymptomatic and immunosuppression predisposes to disease.

40
Q

How does PCP present?

A

diffuse, bilateral ground-glass opacitices on CXR/CT

41
Q

Opacities seen with PCP- look near the back of each lung

A
42
Q

How is PCP diagnosed?

A

lung lavage or lung biopsy

43
Q

How does Pneumocystis jirovecii appear on methanmine silver stain of lung tissue?

A

Disc-dhaped yeast form

44
Q

How is PCP tx?

A

TMP-SMX, pentamidine, dapsone (prophylaxis only), atovaquone (prophylaxis only)- make sure to start prophylaxis when CD4+ count drops below 200/MM3 in HIV pts.

45
Q

What is this?

A

Sporotrichosis (sporothrix schenckii)

46
Q

Describe Sporothrix schenckii

A

dimorphic, cigar-shaped budding yeast that lives on vegetation

47
Q

How is Sporothrix schenckii transmitted?

A

When spores are traumatically introduced into the skin, typically by a thorn (rose gardener’ disease), it causes a local pustule or ulcer with nodules along draining lymphatics (asending lymphangitis)

Disseminated disease possible in immunocompromised hosts

48
Q

How is Sporothrix schenckii tx?

A

itra or posassium iodidi

STEP 1 (4) (18 decks)

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