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MOD II Micro > Fungi > Flashcards

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
Q

Skin scrapings with KOH of Chromoblastomycosis reveal?

A

Copper-colored sclerotic bodies

34
Q

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

A

Murcormycosis

35
Q

Aspergillus produces what toxin and what type of cancer is it associated with?

Often found contaminating what foods, which are common sources?

A
  • Aflatoxin —> hepatocellular carcinoma
  • Peanuts, grain, and rice
36
Q

What is the morphology of Aspergillus fumigatus?

A

Acute angle branching WITH septations

*First 2 letters ‘AS’ –> Acute Septate

37
Q

How is diagnosis of allergic bronchopulmonary asperigillosis made?

A
  • High level of IgE and IgG against aspergillis
  • Sputum culture
  • Wheezing patient and chest X-ray with fleeting infiltrate
38
Q

Who is most at risk for infection by Pneumocystis carinii (P. jiroveci)?

What does it cause?

Most common opportunistic infection in whom?

A
  • Immunocompromised (AIDS, cancer, organ transplant recipients)
  • Severe interstitial pneumonia called Pneumocystis carinii pneumonia (PCP)

*Most common opportunistic infection in AIDS patients

39
Q

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

A
  • Primary lesions in lung –> necrotizing pneumonia
  • Heart valves –> endocarditis
  • Kidney —> renal failure
  • Brain –> ring enhancing lesions
  • Paranasal sinuses may causes necrosis around nose
40
Q

What are the major morphological characteristics of Cryptococcus neoformans?

Only found in what form?

A
  • Heavily encapsulated w/ repeating polysaccharides
  • Only found in yeast form
42
Q

What is the major manifestation of Cryptococcus neoformans infection?

How else can it manifest?

Who is most at risk?

A
  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
Q

What is the key to diagnosis of Cryptococcus neoformans?

What do you expect to see?

A
  • A lumbar puncture then stain with India ink
  • Yeast cells with a surrounding halo, the polysaccharide capsule
44
Q

What stain for tissue samples of Cryptococcus neoformans?

What is another test that relies on the structure of this yeast?

A
  • 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
Q

Who is most at risk for infection by Mucormycosis?

A
  • Diabetics who develop profound DKA
  • Immunocompromised patints, burn patients, and those taking iron chelator deferoxamine, whom are at risk for acidosis
47
Q

What is the morphology of Mucomycetes (Mucormycotina)?

A

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

48
Q

What are the clinical features of Mucormycosis?

A
  • 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
Q

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

A

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

51
Q

Clinical features of PCP?

What is seen on X-ray?

A
  • Present with: fever, SOB, and nonproductive cough
  • Diffuse bilateral interstitial infiltrates, “ground glass” appearance
52
Q

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

What is done to confirm diagnosis?

A

- 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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