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0

What is the morphology of Malassezia furfur?

"Spaghetti and meatballs"

1

What can Malassezia furfur cause?

Pityriasis versicolor

2

What happens in Pityriasis versicolor?

Hypo or hyperpigmented patches on the skin.
Surrounding skin darkens with sunlight while the patches remain white.

3

How do we diagnose Malassezia furfur infection?

KOH prep:
Reveals short, curved, unbranched hyphae, with spherical yeast cells (looks like spaghetti with meatballs).

4

What is the location of the Malassezia furfur infection?

Superficial

5

What is the morphology of Exophiala werneckii?

Brown-pigmented, branched, septate hyphae and budding yeast cells.

6

What can Exophiala werneckii cause?

Tina nigra

7

What happens in tinea nigra?

Dark brown to black patches on the soles of the hands and feet.

8

How do we diagnose Exophiala werneckii?

KOH prep:
Brown pigmented, branched septate hyphae and budding yeast cells.

9

What is the location of Exophiala werneckii infection?

Superficial

10

Where are Microsporum, Trichophyton species, and Epidermophyton floccosum found?

Depending on the particular species:
1. Soil
2. Animals
3. Humans

11

What can Microsporum, Trichophyton, and Epidermophyton floccosum cause?

Dermatophytosis.
Tinea corporis - ringworm
Tinea cruris - jock itch
Tinea pedis - athlete's foot
Tinea capitis - scalp
Tinea unguium - Onychomycosis

12

How do we diagnose Microsporum, Trichophyton, and Epidermophyton floccosum species?

1. KOH: branched hyphae.
2. Wood's light: certain species of Microsporum will fluoresce under UV light.

13

What do Microscporum, Trichophyton, and Epidermophyton floccosum secrete?

Keratinase

14

What is the location of Microsporum, Trichophyton, and Epidermophyton floccosum infection?

Cutaneous

15

Where is Sporothrix schenckii found?

On rose thorns.

16

What can Sporothrix schenckii cause?

Sporotrichosis

17

What happens in sporotrichosis?

1. Subcutaneous nodule gradually appears at site of thorn prick.
2. This nodule becomes necrotic and ulcerates.
3. This ulcer heals but new nodules pop up nearby along the lymphatic tracts.

18

How do we diagnose Sporothrix schenckii?

Dimorphic:
Culture at 25C --> branching hyphae.
Culture at 37C --> yeast cells.

19

What is the location of Sporotrhix schenckii infection?

Subcutaneous

20

Where are Phialophora verrucosa, Cladosporium carrionii, Fonsecaea species found?

These copper-colored soil saprophytes can be found on rotting wood.

21

What is the morphology of Phialophora verrucosa, Cladosporium carrionii, and Fonsecaea species?

Sclerotic bodies: copper colored cells.

22

What can Phialophora verrucosa, Cladosporium carrionii, and Fonsecaea species?

Chromoblastomycosis

23

What happens in chromoblastomycosis?

Following a puncture wound, a small violet wart-like lesion develops.
With time, clusters of these skin lesions can develop. (Resembling cauliflower)

24

How do we diagnose Phialophora verrucosa, Cladosporium carrionii, and Fonsecaea species?

Skin scrappings with KOH prep reveal copper-colored cells, called sclerotic bodies.

25

What is the location of Phialophora verrucosa, Cladosporium carrionii and Fonsecaea species infection?

Subcutaneous

26

Where is Coccidioides immitis found?

1. Desert areas of the southwestern US and northern Mexico.
2. Respiratory transmission.

27

What is the morphology of Coccidioides immitis?

Dimorphic:
1. Mycelial forms with spores at 25C.
2. Yeast forms at 37C.

28

What happens in Coccidioidomycosis?

1. Asymptomatic (in most persons)
2. Pneumonia
3. Disseminated --> affects lung, skin, bones, meninges.

29

What is useful to keep in mind about coccidioidomycosis?

A small percentage of individuals with this infection will develop painful erythematous nodular lesions called erythema nodosum.

30

How do we diagnose Coccidioides immitis infection?

1. Biopsy of affected tissue: lung biopsy, skin biopsy etc.
a. Silver stain or KOH prep.
b. Culture on Sabouraud's agar.
2. Serology
3. Skin test

31

What is the location of Coccidioides immitis infection?

Systemic

32

Where is Histoplasma capsulatum found?

1. Mississippi valley
2. Present in bird and bat droppings

33

How is Histoplasma capsulatum transmitted?

Via respiratory route

34

What happens in Histoplasmosis?

1. Asymptomatic (in most persons).
2. Pneumonia: lesions calcify (similar to TB).
3. Disseminated --> any organ, most commonly lung, liver, spleen.

35

How do we diagnose histoplasmosis?

1. Lung biopsy - silver stain specimen/ culture on Sabouraud's agar will reveal dimorphic fungi.
2. Serology
3. Skin test
4. Urine antigen test

36

What is important to remember about Histoplasma capsulatum?

Can survive intracellularly within macrophages.

37

What is the location of Histoplasma capsulatum infection?

Systemic

38

Where is Blastomyces dermatitidis found?

1. Mississippi River valley extending north to the Great Lakes.
2. In soil or rotten wood.

39

What is the morphology of Blastomyces dermatitidis?

Dimorphic:
Myceliac forms with spores at 25C.
Yeast forms at 37C.

40

What happens in blastomycosis?

1. Asymptomatic (uncommon)
2. Pneumonia: rarely calcifications.
3. Disseminated: (most common).
4. Cutaneous: skin ulcers.

41

How do we diagnose Blastomyces dermatitidis?

1. Biopsy of affected tissue: lung, skin, etc.
2. Serology
3. Skin test

42

What is the location of Blastomyces dermatitidis infection?

Systemic

43

Where is Cryptococcus gattii (not neoformans) found?

In soil. (neoformans in pigeon droppings)

44

What is the morphology of Cryptococcus neoformans?

1. Polysaccharide capsule
2. Yeast form ONLY (not dimorphic).

45

What happens in Cryptococcosis?

1. Subacute or chronic meningitis
2. Pneumonia - usually self-limited.
3. Skin lesions - looks like acne.

46

How do we diagnose Cryptococcus neoformans infection?

1. India-ink stain of CSF: observe encapsulated yeast.
2. Cryptococcal antigen test of CSF --> detects polysaccharide antigens.
3. Fungal culture.

47

What is important to remember about Cryptococcosis?

Most cases occur in immunocompromised patients.

48

What is the location of Cryptococcus neoformans infection?

Systemic

49

Where is C.albicans found?

1. Normal inhabitant of the skin, mouth, and GI tract.
2. NOT in blood.

50

What is the morphology of C.albicans?

Pseudohyphae and yeast.

51

What happens in Candidiasis in a normal host?

1. Oral thrush
2. Vulvovaginal candidiasis
3. Cutaneous --> diaper rash, rash in the skin folds of obese individuals.

52

What happens in candidiasis in an immunocompromised host?

1. Thrush, vaginitis, and/or cutaneous.
2. Esophageal --> retrosternal chest pain, dysphagia etc.
3. Disseminated candidiasis (very sick hospitalized patients).
4. Chronic mucocutaneous candidiasis.

53

How do we diagnose C.albicans infection?

1. KOH stain of specimen.
2. Silver stain of specimen.
3. Blood culture --> growth must be respected.
4. Blood assay for beta-D-glucan.

54

What is the location of C.albicans infection?

Cutaneous or systemic (normal host, or opportunistic).

55

What are the three main pathogenic species of Aspergillus?

A.fumigatus
A.flavus
A.niger

56

Where is Aspergillus found?

1. Everywhere (frequent lab contaminant).
2. Aspiration of Aspergillus --> asthma.

57

What is the morphology of Aspergillus?

Branching septated hyphae.

58

What are the 4 forms of Aspergillosis?

1. Allergic bronchopulmonary aspergillosis.
2. Aspergilloma
3. Invasive aspergillosis
4. Aflatoxin

59

What happens in allergic bronchopulmonary aspergillosis?

IgE mediated - asthma type reaction with shortness of breath and high fever.

60

What happens in aspergilloma?

Fungus ball - associated with hemoptysis.

61

What happens in invasive aspergillosis?

Necrotizing pneumonia - may disseminate to other organs in immunocompromised patients.

62

What can cause aflatoxin consumption?

Aflatoxin produced by A.flavus, can cause liver damage and liver cancer.

63

How do we diagnose allergic bronchopulmonary aspergillosis?

1. High level of IgE and IgG against Aspergillus.
2. Sputum culture
3. Wheezing patient
4. Increased eosinophils
5. Skin test - immediate HSR

64

How do we diagnose Aspergilloma?

With chest X-Ray or CT scan.

65

How do we diagnose invasive aspergillosis?

Sputum examination and culture.

66

Where are Rhizopus, Rhizomucor, and Mucor found?

Saprophytic molds.

67

What is the morphology of Rhizopus, Rhizomucor, and Mucor?

Broad, non-septated branching hyphae.

68

What happens in Mucormycosis?

1. Rhinocerebral (diabetes association) --> starts on nasal mucosa and invades the sinus and orbit.
2. Pulmonary mucormycosis.

69

How do we diagnose Mucormycosis?

Biopsy and black nasal discharge.

70

What is important to remember about Mucormycosis?

This disease is rapidly fatal.

71

Where is Actinomyces israelii found?

Part of the normal flora of the mouth and GI tract.

72

What is the morphology of Actinomyces israelii?

1. Gram(+) rods
2. Anaerobic
3. Grow as branching chains or beaded filaments.

73

What can Actinomyces israelii cause?

Eroding abscesses of the mouth, lung, or GI tract:
1. Cervicofacial actinomycosis
2. Thoracic actinomycosis
3. Abdominal actinomycosis

74

How do we diagnose A.israelii infection?

1. Examine tissue or pus from infection site, and look for sulfur granules.
2. Anaerobic culture.

75

What are the yellow "sulfur granules"?

Microcolonies of Actinomyces and cellular debris.

76

Where is Nocardia asteroides found?

Never part of the normal flora.

77

How is Nocardia asteroides transmitted?

Respiratory route

78

What is the morphology of N.asteroides?

1. Gram(+) rods
2. Partially acid-fast
3. Aerobic
4. Grow as branching chains or beaded filaments.

79

What can N.asteroides cause?

1. Pneumonia
2. Formation of abscesses in the lung, kidney, and CNS.

80

How do we diagnose N.asteroides?

1. Gram stain
2. Modified acid fast stain - decolorize with 1% sulfuric acid instead of acid alcohol.
3. Aerobic culture.

81

What is important to keep in mind about Nocardia infections?

Usually occur in immunocompromised patients.