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Microbiology > Fungi > Flashcards

Fungi Flashcards

0
Q

What can Malassezia furfur cause?

A

Pityriasis versicolor

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1
Q

What is the morphology of Malassezia furfur?

A

“Spaghetti and meatballs”

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2
Q

What happens in Pityriasis versicolor?

A

Hypo or hyperpigmented patches on the skin.

Surrounding skin darkens with sunlight while the patches remain white.

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3
Q

How do we diagnose Malassezia furfur infection?

A

KOH prep:

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

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4
Q

What is the location of the Malassezia furfur infection?

A

Superficial

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5
Q

What is the morphology of Exophiala werneckii?

A

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

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6
Q

What can Exophiala werneckii cause?

A

Tina nigra

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7
Q

What happens in tinea nigra?

A

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

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8
Q

How do we diagnose Exophiala werneckii?

A

KOH prep:

Brown pigmented, branched septate hyphae and budding yeast cells.

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9
Q

What is the location of Exophiala werneckii infection?

A

Superficial

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10
Q

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

A

Depending on the particular species:

  1. Soil
  2. Animals
  3. Humans
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11
Q

What can Microsporum, Trichophyton, and Epidermophyton floccosum cause?

A 
Dermatophytosis.
Tinea corporis - ringworm
Tinea cruris - jock itch
Tinea pedis - athlete's foot
Tinea capitis - scalp
Tinea unguium - Onychomycosis
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12
Q

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

A
  1. KOH: branched hyphae.

2. Wood’s light: certain species of Microsporum will fluoresce under UV light.

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13
Q

What do Microscporum, Trichophyton, and Epidermophyton floccosum secrete?

A

Keratinase

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14
Q

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

A

Cutaneous

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15
Q

Where is Sporothrix schenckii found?

A

On rose thorns.

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16
Q

What can Sporothrix schenckii cause?

A

Sporotrichosis

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17
Q

What happens in sporotrichosis?

A
  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.
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18
Q

How do we diagnose Sporothrix schenckii?

A

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

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19
Q

What is the location of Sporotrhix schenckii infection?

A

Subcutaneous

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20
Q

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

A

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

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21
Q

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

A

Sclerotic bodies: copper colored cells.

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22
Q

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

A

Chromoblastomycosis

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23
Q

What happens in chromoblastomycosis?

A

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

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24
Q

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

A

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

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25
Q

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

A

Subcutaneous

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26
Q

Where is Coccidioides immitis found?

A
  1. Desert areas of the southwestern US and northern Mexico.

2. Respiratory transmission.

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27
Q

What is the morphology of Coccidioides immitis?

A

Dimorphic:

  1. Mycelial forms with spores at 25C.
  2. Yeast forms at 37C.
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28
Q

What happens in Coccidioidomycosis?

A
  1. Asymptomatic (in most persons)
  2. Pneumonia
  3. Disseminated –> affects lung, skin, bones, meninges.
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29
Q

What is useful to keep in mind about coccidioidomycosis?

A

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

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30
Q

How do we diagnose Coccidioides immitis infection?

A
  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
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31
Q

What is the location of Coccidioides immitis infection?

A

Systemic

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32
Q

Where is Histoplasma capsulatum found?

A
  1. Mississippi valley

2. Present in bird and bat droppings

33
Q

How is Histoplasma capsulatum transmitted?

A

Via respiratory route

34
Q

What happens in Histoplasmosis?

A
  1. Asymptomatic (in most persons).
  2. Pneumonia: lesions calcify (similar to TB).
  3. Disseminated –> any organ, most commonly lung, liver, spleen.
35
Q

How do we diagnose histoplasmosis?

A
  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
Q

What is important to remember about Histoplasma capsulatum?

A

Can survive intracellularly within macrophages.

37
Q

What is the location of Histoplasma capsulatum infection?

38
Q

Where is Blastomyces dermatitidis found?

A
  1. Mississippi River valley extending north to the Great Lakes.
  2. In soil or rotten wood.
39
Q

What is the morphology of Blastomyces dermatitidis?

A

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

40
Q

What happens in blastomycosis?

A
  1. Asymptomatic (uncommon)
  2. Pneumonia: rarely calcifications.
  3. Disseminated: (most common).
  4. Cutaneous: skin ulcers.
41
Q

How do we diagnose Blastomyces dermatitidis?

A
  1. Biopsy of affected tissue: lung, skin, etc.
  2. Serology
  3. Skin test
42
Q

What is the location of Blastomyces dermatitidis infection?

43
Q

Where is Cryptococcus gattii (not neoformans) found?

A

In soil. (neoformans in pigeon droppings)

44
Q

What is the morphology of Cryptococcus neoformans?

A
  1. Polysaccharide capsule

2. Yeast form ONLY (not dimorphic).

45
Q

What happens in Cryptococcosis?

A
  1. Subacute or chronic meningitis
  2. Pneumonia - usually self-limited.
  3. Skin lesions - looks like acne.
46
Q

How do we diagnose Cryptococcus neoformans infection?

A
  1. India-ink stain of CSF: observe encapsulated yeast.
  2. Cryptococcal antigen test of CSF –> detects polysaccharide antigens.
  3. Fungal culture.
47
Q

What is important to remember about Cryptococcosis?

A

Most cases occur in immunocompromised patients.

48
Q

What is the location of Cryptococcus neoformans infection?

49
Q

Where is C.albicans found?

A
  1. Normal inhabitant of the skin, mouth, and GI tract.

2. NOT in blood.

50
Q

What is the morphology of C.albicans?

A

Pseudohyphae and yeast.

51
Q

What happens in Candidiasis in a normal host?

A
  1. Oral thrush
  2. Vulvovaginal candidiasis
  3. Cutaneous –> diaper rash, rash in the skin folds of obese individuals.
52
Q

What happens in candidiasis in an immunocompromised host?

A
  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
Q

How do we diagnose C.albicans infection?

A
  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
Q

What is the location of C.albicans infection?

A

Cutaneous or systemic (normal host, or opportunistic).

55
Q

What are the three main pathogenic species of Aspergillus?

A

A.fumigatus
A.flavus
A.niger

56
Q

Where is Aspergillus found?

A
  1. Everywhere (frequent lab contaminant).

2. Aspiration of Aspergillus –> asthma.

57
Q

What is the morphology of Aspergillus?

A

Branching septated hyphae.

58
Q

What are the 4 forms of Aspergillosis?

A
  1. Allergic bronchopulmonary aspergillosis.
  2. Aspergilloma
  3. Invasive aspergillosis
  4. Aflatoxin
59
Q

What happens in allergic bronchopulmonary aspergillosis?

A

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

60
Q

What happens in aspergilloma?

A

Fungus ball - associated with hemoptysis.

61
Q

What happens in invasive aspergillosis?

A

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

62
Q

What can cause aflatoxin consumption?

A

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

63
Q

How do we diagnose allergic bronchopulmonary aspergillosis?

A
  1. High level of IgE and IgG against Aspergillus.
  2. Sputum culture
  3. Wheezing patient
  4. Increased eosinophils
  5. Skin test - immediate HSR
64
Q

How do we diagnose Aspergilloma?

A

With chest X-Ray or CT scan.

65
Q

How do we diagnose invasive aspergillosis?

A

Sputum examination and culture.

66
Q

Where are Rhizopus, Rhizomucor, and Mucor found?

A

Saprophytic molds.

67
Q

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

A

Broad, non-septated branching hyphae.

68
Q

What happens in Mucormycosis?

A
  1. Rhinocerebral (diabetes association) –> starts on nasal mucosa and invades the sinus and orbit.
  2. Pulmonary mucormycosis.
69
Q

How do we diagnose Mucormycosis?

A

Biopsy and black nasal discharge.

70
Q

What is important to remember about Mucormycosis?

A

This disease is rapidly fatal.

71
Q

Where is Actinomyces israelii found?

A

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

72
Q

What is the morphology of Actinomyces israelii?

A
  1. Gram(+) rods
  2. Anaerobic
  3. Grow as branching chains or beaded filaments.
73
Q

What can Actinomyces israelii cause?

A

Eroding abscesses of the mouth, lung, or GI tract:

  1. Cervicofacial actinomycosis
  2. Thoracic actinomycosis
  3. Abdominal actinomycosis
74
Q

How do we diagnose A.israelii infection?

A
  1. Examine tissue or pus from infection site, and look for sulfur granules.
  2. Anaerobic culture.
75
Q

What are the yellow “sulfur granules”?

A

Microcolonies of Actinomyces and cellular debris.

76
Q

Where is Nocardia asteroides found?

A

Never part of the normal flora.

77
Q

How is Nocardia asteroides transmitted?

A

Respiratory route

78
Q

What is the morphology of N.asteroides?

A
  1. Gram(+) rods
  2. Partially acid-fast
  3. Aerobic
  4. Grow as branching chains or beaded filaments.
79
Q

What can N.asteroides cause?

A
  1. Pneumonia

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

80
Q

How do we diagnose N.asteroides?

A
  1. Gram stain
  2. Modified acid fast stain - decolorize with 1% sulfuric acid instead of acid alcohol.
  3. Aerobic culture.
81
Q

What is important to keep in mind about Nocardia infections?

A

Usually occur in immunocompromised patients.

Microbiology (46 decks)

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