Fungi

Question 1

Geographic location of Histoplasma capsulatum?

What is it found in and how is it transmitted?

Answer 1

• 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

Question 3

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

Answer 3

Macrophages with intracellular oval bodies (ovoid bodies)

Question 4

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

Answer 4

• 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”

Question 5

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

Answer 5

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)

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

Geographic location of Blastomycosis dermatitidis?

Transmitted how?

Answer 8

• Great lakes and Ohio River Valley
• Inhalation of aerosolized spores

Question 9

What is the most prominent morophological characteristic of Malassezia furfur?

Answer 9

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

- Spaghetti = hyphae

• Meatballs = spherical yeast

Question 10

Infection by Malassezia furfur​ causes what condition?

Manifests how?

Answer 10

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

- Confined to the STRATUM CORNEUM

Question 11

Geographic location of C**occidioides immitis?

Route of transmission?

Second most common opportunisitc infection in whom?

Answer 11

• 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!

Question 14

Exophiala werneckii is responsible for what superficial fungal infection?

Manifests how?

Answer 14

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

Question 15

Where is Sporothrix schneckii found?

Causes what condition?

Answer 15

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

Question 16

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

Answer 16

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

Question 17

Microsporum, Trichophyton, and Epidermophyton are the common?

Answer 17

Dermatophytes

Question 18

What are 3 common sources of dermatophytes?

Answer 18

1. Soil
2. Animals
3. Humans

Question 19

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

What specifically in infants?

Answer 19

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

Question 20

In immunocompromised patients what does Candida albicans lead to?

Important implication in IV drug users?

Answer 20

• 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

Question 21

How is the diagnosis of Dermatophytosis made?

What specific method for Microsporum species?

Answer 21

• KOH prep of skin scrapings: branched hyphae

- Woods light to diagnose Microsporum will fluoresce under UV light

Question 24

Aspergillus fumigatus causes what 3 major types of disease?

What are the important characteristics of each?

Answer 24

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)

Question 25

Microscopic examination of Sporothrix schneckii reveals?

Answer 25

Cigar shaped yeast cells that reproduce by budding

Question 26

What is the morphology of Candida albicans based on temperature?

Answer 26

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

Question 29

How is diagnosis of Candida albicans made?

Answer 29

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

Question 30

Where in nature is Cryptococcus neoformans found?

How is it transmitted?

Answer 30

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

Question 31

Phialophora and Cladosporium cause what fungal disease?

How does it manifest?

Answer 31

• Chromoblastomycosis
• Following puncture wound, a small, violet, wart-like lesion
• Over months-years, additional warts arise and eventually clusters of lesions resemble cauliflower

Question 32

Skin scrapings with KOH of Chromoblastomycosis reveal?

Answer 32

Copper-colored sclerotic bodies

Question 34

*Rhizopus, Rhizomucor, and Mucor (Mucormycotina)* are fungi responsbile for which opportunistic disease?

Answer 34

Murcormycosis

Question 35

*Aspergillus* produces what toxin and what type of cancer is it associated with? Often found contaminating what foods, which are common sources?

Answer 35

- Aflatoxin ---\> **hepatocellular carcinoma** - Peanuts, grain, and rice

Question 36

What is the morphology of *Aspergillus fumigatus?*

Answer 36

**Acute angle branching** WITH **septations** **\***First 2 letters '**AS**' --\> **A**cute **S**eptate

Question 37

How is diagnosis of allergic bronchopulmonary asperigillosis made?

Answer 37

- High level of **IgE** and **IgG** against aspergillis - Sputum culture - Wheezing patient and chest X-ray with fleeting infiltrate

Question 38

Who is most at risk for infection by *Pneumocystis carinii (P. jiroveci)?* What does it cause? Most common opportunistic infection in whom?

Answer 38

- Immunocompromised (AIDS, cancer, organ transplant recipients) - Severe interstitial pneumonia called ***Pneumocystis carinii pneumonia (PCP)*** **\*Most common** opportunistic infection in **AIDS** patients

Question 39

Which organs and tissues are most often affected by Angioinvasive aspergillosis?

Answer 39

- Primary lesions in **lung** --\> **necrotizing pneumonia** - Heart valves --\> **endocarditis** - Kidney ---\> **renal failure** - Brain --\> **ring enhancing lesions** - **Paranasal sinuses** may causes necrosis around nose

Question 40

What are the major morphological characteristics of *Cryptococcus neoformans?* Only found in what form?

Answer 40

- **Heavily encapsulated** w/ **repeating polysaccharides** - Only found in **yeast** form

Question 42

What is the major manifestation of *Cryptococcus neoformans* infection? How else can it manifest? Who is most at risk?

Answer 42

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

Question 43

What is the key to diagnosis of *Cryptococcus neoformans*? What do you expect to see?

Answer 43

- A **lumbar puncture** then stain with **India ink** - Yeast cells with a surrounding **halo**, the **polysaccharide capsule**

Question 44

What stain for tissue samples of *Cryptococcus neoformans?* What is another test that relies on the structure of this yeast?

Answer 44

- Stain with **mucicarmine (red)** or **methanamine (silver)** - Can do **latex agglutination test** to detect repeating polysaccharide capsular antigen w/ antibody-coated beads causing agglutination

Question 46

Who is most at risk for infection by *Mucormycosis?*

Answer 46

- **Diabetics** who develop profound **DKA** - Immunocompromised patints, burn patients, and those taking iron chelator **deferoxamine**, whom are at risk for **acidosis**

Question 47

What is the morphology of *Mucomycetes (Mucormycotina)?*

Answer 47

**Hyphae** are **NON-septate rods** w/ **wide/right** **angle branching (90°)**

Question 48

What are the clinical features of *Mucormycosis*?

Answer 48

- 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**

Question 50

What is the relationship between CD4 count and development of PCP?

Answer 50

When CD4+ count is **below 200** there is increased risk of infection

Question 51

Clinical features of PCP? What is seen on X-ray?

Answer 51

- Present with: fever, SOB, and nonproductive cough - Diffuse bilateral interstitial infiltrates, "**ground glass" appearance**

Question 52

How is diagnosis of infection with *Pneumocystis carinii (jiroveci)* made; what characteristic shape are you looking for? What is done to confirm diagnosis?

Answer 52

**- Silver stain** of alveolar lung secretions, revealing the **saucer-appearing fungi** **- Bronchoalveolar lavage** or **Biopsy** by **bronchoscopy** to confirm the diagnosis