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Fungi Flashcards

1
Q

Geographic location of Histoplasma capsulatum?

What is it found in and how is it transmitted?

A
  • Midwestern and central US; along the Mississippi and Ohio River Valley
  • Associated with bird or bat droppings. People in caves or cleaning chicken coops
  • Transmitted through inhalation of spores into respiratory tract and then ingested by macrophages
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3
Q

What is the histological characteristic of macrophages that have picked up Histoplasma capsulatum?

A

Macrophages with intracellular oval bodies (ovoid bodies)

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4
Q

How does the structure of Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioides immitis change based on temperature?

A
  • Dimorphic
  • At 25 °C they grow as mycelia (mold)
  • Inside body at 37 °C they are a yeast

*Coccidioidesformsspherules filled with endospores inside lungs

“Mold in the cold, yeast in the heat”

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5
Q

How is the diagnosis of Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioiodes immitis made?

A

1) Best diagnosed with biopsy of affected tissue - examined with silver stain or KOH prep
2) Serologic testing: rapid serum antigen test
3) Urine rapid antigen test (quickest)

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6
Q

What is the disease mechanism for Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioiodes immitis?

A
  • Once inhaled, cause local infection in the lung
  • Followed by bloodstream dissemination
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7
Q

What are the 3 clinical presentations for Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidioiodes immitis?

A

1) Asymptomatic: majority of cases or mild respiratory illness
2) Pneumonia: mild w/ fever, cough, and chest X-ray infiltrates. Like Tb, granulomas with calcifications can follow resolution.
- Minority will develop chronic pneumonia and even less will progress to a chronic cavitary pneumonia
3) Disseminated, rarely can cause meningitis, bone lytic granulomas (osteomyelitis), skin granulomas (erythema nodosum), and organ leisions –> Most often in immunocompromised

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8
Q

Geographic location of Blastomycosis dermatitidis?

Transmitted how?

A
  • Great lakes and Ohio River Valley
  • Inhalation of aerosolized spores
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9
Q

What is the most prominent morophological characteristic of Malassezia furfur?

A
  • “Spaghetti and meatball” appearane on KOH prep of skin scrapings

- Spaghetti = hyphae

  • Meatballs = spherical yeast
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10
Q

Infection by Malassezia furfur​ causes what condition?

Manifests how?

A
  • Pityriasis versicolor (tinea versicolor)
  • Superficial fungal infection causing hypo- and/or hyerpigmented patches of skin on back and chest

- Confined to the STRATUM CORNEUM

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11
Q

Geographic location of C**occidioides immitis?

Route of transmission?

Second most common opportunisitc infection in whom?

A
  • Found in the Southwestern U.S. (AZ, NM, SoCal)
  • Inhalation of aerolized spores in dust
  • 2nd most common opportunistic infection in AIDS patients who have resided in Arizona!
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14
Q

Exophiala werneckii is responsible for what superficial fungal infection?

Manifests how?

A
  • Tinea nigra
  • Dark brown to black painless patches on the soles of the hands and feet
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15
Q

Where is Sporothrix schneckii found?

Causes what condition?

A
  • Soil and on plants (rose thorns and splinters)
  • Rose gardener’s disease
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16
Q

Following a prick by a thorn contaminated with Sporothrix schneckii what occurs?

A
  • Nodule at site of trauma becomes necrotic and ulcerates
  • Infections spreads in ascending pattern along the path of draining lymphatic’s
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17
Q

Microsporum, Trichophyton, and Epidermophyton are the common?

A

Dermatophytes

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18
Q

What are 3 common sources of dermatophytes?

A
  1. Soil
  2. Animals
  3. Humans
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19
Q

In normal hosts (immunocompetent) infection by Candida albicans causes?

What specifically in infants?

A

1) Oral thrush: patches of creamy white exudate w/ a reddish base
2) Vaginitis: frequently when taking antibiotics, OCs, or during menses
3) Diaper rash: due to heat/humidity within diaper

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20
Q

In immunocompromised patients what does Candida albicans lead to?

Important implication in IV drug users?

A
  • Candidal esophagitis often seen in HIV or diabetic patients
  • Dissemination: NOT normally found in blood, but can invade almost any organ if it enters
  • Renal, myocardial, and brain abscesses
  • Can invade eye and cause endopthalmitis
  • ENDOCARDITIS often tricuspid in IV drug users
21
Q

How is the diagnosis of Dermatophytosis made?

What specific method for Microsporum species?

A
  • KOH prep of skin scrapings: branched hyphae

- Woods light to diagnose Microsporum will fluoresce under UV light

24
Q

Aspergillus fumigatus causes what 3 major types of disease?

What are the important characteristics of each?

A

1) Allergic bronchopulmonary pergillosis (ABPA) - type I hypersensitivity - wheezing, fever, migratory pulmonary infiltrate - IgE mediated
2) Aspergillomas - infection in preformed lung cavities (from TB or malignancies) - fungal ball
3) Angioinvasive aspergillosis - affecting immunocompromised (pt’s with neutropenia following chemo or on high dose steroids for tx of GVHD)

25
Q

Microscopic examination of Sporothrix schneckii reveals?

A

Cigar shaped yeast cells that reproduce by budding

26
Q

What is the morphology of Candida albicans based on temperature?

A

Pseudo hyphae at 25 °C and germ tubes at 37 °C

29
Q

How is diagnosis of Candida albicans made?

A
  • KOH stain of specimen
  • Silver stain of specimen
  • Blood culture: growth must be respected (not normally in blood)
  • Blood assay for beta-D-glucan
30
Q

Where in nature is Cryptococcus neoformans found?

How is it transmitted?

A
  • Found in soil, but most often pigeon droppings
  • Via inhalation and settles in lung as primary focus before disseminating
31
Q

Phialophora and Cladosporium cause what fungal disease?

How does it manifest?

A
  • Chromoblastomycosis
  • Following puncture wound, a small, violet, wart-like lesion
  • Over months-years, additional warts arise and eventually clusters of lesions resemble cauliflower
32
Skin scrapings with KOH of Chromoblastomycosis reveal?
Copper-colored sclerotic bodies
34
*Rhizopus, Rhizomucor, and Mucor (Mucormycotina)* are fungi responsbile for which opportunistic disease?
Murcormycosis
35
*Aspergillus* produces what toxin and what type of cancer is it associated with? Often found contaminating what foods, which are common sources?
- Aflatoxin ---\> **hepatocellular carcinoma** - Peanuts, grain, and rice
36
What is the morphology of *Aspergillus fumigatus?*
**Acute angle branching** WITH **septations** **\***First 2 letters '**AS**' --\> **A**cute **S**eptate
37
How is diagnosis of allergic bronchopulmonary asperigillosis made?
- High level of **IgE** and **IgG** against aspergillis - Sputum culture - Wheezing patient and chest X-ray with fleeting infiltrate
38
Who is most at risk for infection by *Pneumocystis carinii (P. jiroveci)?* What does it cause? Most common opportunistic infection in whom?
- Immunocompromised (AIDS, cancer, organ transplant recipients) - Severe interstitial pneumonia called ***Pneumocystis carinii pneumonia (PCP)*** **\*Most common** opportunistic infection in **AIDS** patients
39
Which organs and tissues are most often affected by Angioinvasive aspergillosis?
- Primary lesions in **lung** --\> **necrotizing pneumonia** - Heart valves --\> **endocarditis** - Kidney ---\> **renal failure** - Brain --\> **ring enhancing lesions** - **Paranasal sinuses** may causes necrosis around nose
40
What are the major morphological characteristics of *Cryptococcus neoformans?* Only found in what form?
- **Heavily encapsulated** w/ **repeating polysaccharides** - Only found in **yeast** form
42
What is the major manifestation of *Cryptococcus neoformans* infection? How else can it manifest? Who is most at risk?
1. **Subacute or chronic meningitis**: headache, fever, vomiting, neuro deficits --\> **Most common** cause of fungal meningitis (**meningoencephalitis**) 2. **Pneumonia**: usually self-limited 3. **Skin lesions**: which resemble acne \*Most often affects immunocompromised pt's w/ AIDS, leukemi, lymphoma, SLE, or transplant recipients
43
What is the key to diagnosis of *Cryptococcus neoformans*? What do you expect to see?
- A **lumbar puncture** then stain with **India ink** - Yeast cells with a surrounding **halo**, the **polysaccharide capsule**
44
What stain for tissue samples of *Cryptococcus neoformans?* What is another test that relies on the structure of this yeast?
- Stain with **mucicarmine (red)** or **methanamine (silver)** - Can do **latex agglutination test** to detect repeating polysaccharide capsular antigen w/ antibody-coated beads causing agglutination
46
Who is most at risk for infection by *Mucormycosis?*
- **Diabetics** who develop profound **DKA** - Immunocompromised patints, burn patients, and those taking iron chelator **deferoxamine**, whom are at risk for **acidosis**
47
What is the morphology of *Mucomycetes (Mucormycotina)?*
**Hyphae** are **NON-septate rods** w/ **wide/right** **angle branching (90°)**
48
What are the clinical features of *Mucormycosis*?
- Fungi proliferate in vessel wall where there is extra **glucose and ketones** - After BV invasion, penetration of **cribiform plate** and invasion of brain - Necrosis of tissus --\> **Rhinocerebral mucormycosis** - Can also cause **pulmonary mucormycosis**
50
What is the relationship between CD4 count and development of PCP?
When CD4+ count is **below 200** there is increased risk of infection
51
Clinical features of PCP? What is seen on X-ray?
- Present with: fever, SOB, and nonproductive cough - Diffuse bilateral interstitial infiltrates, "**ground glass" appearance**
52
How is diagnosis of infection with *Pneumocystis carinii (jiroveci)* made; what characteristic shape are you looking for? What is done to confirm diagnosis?
**- Silver stain** of alveolar lung secretions, revealing the **saucer-appearing fungi** **- Bronchoalveolar lavage** or **Biopsy** by **bronchoscopy** to confirm the diagnosis

MOD II Micro (8 decks)

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