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56 Cards in this Set

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  • Back
What is the only encapsulated yeast:
Cryptococcus neoformans has a polysaccharide capsule
Where do people get Cryptococcus neoformans?
Pigeon droppings and soil
Who gets disease from Cryptococcus?
Normal and IC hosts
7-8% of AIDS pts
Most common predisposing factor for Cryptococcus in non-AIDs patients:

Other predisposing factors:
Large doses of adrenal corticosteroids

Sarcoidosis and lymphoma
How do you acquire Cryptococcus infection?
Inhalation into lungs (no case clustering)
Cryptococcus infections in immunocompetent patients are:

Pulmonary infections may be:

Symp or asymp
What is the major infection of concern with Cryptococcus and how does it occur?
Hematogenous spread to CNS occurs even w/ subclinical infections
Pathogenesis of Cryptococcus

What does the capsule do?

How is infection cleared?
Capsule blocks phagocytosis, interferes w/ complement pathway

Activated T-cells required for clearing of infection (recovery w/ humoral immunity – people get antibodies to it)
How do most people w/ Cryptococcus present?
Meningoencephalitis: HA, nausea, gait problems, dementia, irritability, cranial nerve problems and hydrocephalus, mild fever and nuchal rigidity
What happens to people who go untreated for Cryptococcus?
Deepening coma if untreated → death
What does Cryptococcus look like on chest X-ray?

Other organs affected:
Well-localized infiltrates

Skin, bone, prostate, other GU sites, hepatitis, pericarditis, endocarditis, endophthalmitis
What occurs w/ disseminated Cryptococcus infections?
Raised skin lesions in immunocompromised pts
Cryptococcus virulence factors (3):
1. polysaccharide capsule – India Ink or Capsule stain
2. phenol oxidase enzyme – produces melanin; prevents formation of toxic hydroxy radicals and thus protects fungal cell form oxidative stress and immune defense mechanisms of the host
3. can grow at 37 C (i.e. human body temp)
Lab diagnosis - Cryptococcus on culture:
Distinctive brown colonies
For rapid diagnosis of Cryptococcus:
India Ink stain shows large white capsule surrounding the yeast
What is the best test for picking up Cryptococcus? Uses?
Cryptococcal Antigen Latex Agglutination test
Detects antigen in CSF and serum; best for patients w/ cryptococcal meningitis
What histopathological methods are used for Cryptococcus? (3)
1. PAS/GMS – stains the cell body but not the capsule
2. Mucicarmine – stains capsular material
3. Methenamine silver (GMS) stain
What is Cryptococcus potential confused for and what test does not allow for this confusion?
Coccidiodes immitis; use Mucicarmine stain
What type of fungus is H. capsulatum?

Where is the yeast phase found?

What does the mold phase have?
Dimorphic fungus

Yeast phase found in macrophages

Mold phase has tuberculate macroconidia
Does H. capsulatum have a capsule?
Where is H. capsulatum found and in what region of the country?
Soil, bird, and bat droppings

Ohio/Mississippi River Valleys (Chicago is on fringe of endemic area)
3 ways that Histoplasmosis may present clinically?
1. asymptomatic – antibody present
2. pulmonary – infiltrates and mediastinal lymphadenopathy*; cavitating lesion; fever, night sweats, weight loss (like TB)*
3. disseminated – febrile illness; spread to CNS, skin, adrenals; large liver and spleen
What is the hallmark of H. capsulatum?**
Infection of RE by yeasts growing in macrophages**
Where can Histoplasma yeast spread?
Liver, spleen, bone marrow*
Primary lesion of Histoplasmosis?
Granuloma in lung (do sputum sample)
3 ways to diagnose Histoplasmosis?
1. culture of bone marrow, biopsy, BAL – convert mold to yeast (diagnostic); DNA probe of colony
2. skin test – positive test shows past exposure; not used to diagnose acute infection
3. urine antigen test – very sensitive; diagnosis of Histoplasma and Blastomyces
What does Histoplasmosis look like histologically?
Intracellular yeast form in multinucleate giant cell

Looks like they have capsules, but they do not
What techniques can be used to diagnose Histoplasmosis?
1. Culture media: slow growing colonies; look at both sides of plate (white and brown)

2. Stain: septate hyphae*, right angles; has micro- and macroconidia; macroconidia are tuberculate w/ fingerlike projections (“Mariner’s wheel” on a ship)
**Major characteristic of Blastomyces dermatitides?**
broad-based budding**
Where is Blasto found and what is it associated with?
central U.S.

in soil and wood
Other name for Blastomycosis?
Chicago disease
What animal other than humans can be infected by Blasto?
dogs: they tell you that Blasto is in an area
Clinical manifestations of Blasto? (4)
1. pulmonary
2. skin lesions
3. lytic bone lesions
4. disseminated disease
2 types of pneumonia seen with Blasto infections?
1. acute self-limited: resolves in one month

2. chronic pneumo: progressive course, abnormal chest X-ray in 2/3
What may skin lesions due to Blasto progress to?
large ulcers
What histological stains can be used for Blasto and what is seen?
stains: GMS, PAS

large, broad-based budding yeast are observed
Lab diagnosis of Blasto:
1. broad-based budding yeast on KOH prep (BBB!)

2. septate hyphae and unbranched short conidiophores ("lollipop shaped")

(Coccidiodes immitis)

"San Joaquin Valley Fever"
"Desert Rheumatism"
What does Coccidiodes immitis look like:

in tissue?

in culture?
tissue: spherule filled w/ endospores

culture: mold* w/ barrel-shaped arthroconidia
Is Coccidioides transmitted person-to-person?
Pathogenesis of Coccidioides?
inhale arthroconidia --> into alveoli --? monocytes ingest arthroconidia --> they become spherules
Clinical manifestations of Coccidiomycosis?
1. primary infection: fever, cough, chest pain, malaise, hypersensitivity; infiltrates on chest X-ray w/ hilar lymphadenopathy or pleural effusion; mild eosinophilia --> usually resolves spontaneously

2. dissemination to bone, skin, squamous and mucosal tissues, meninges, joints, etc. can follow primary resp infection

3. Erythema nodosum* - rash is an immunologic response to fungus; usually seen in white women
4 methods of lab diagnosis for Coccidiomycosis:
1. micro exam: detects spherules*
2. culture: alternating arthroconidia; DNA probe of colony
3. positive skin test (1-4 weeks)
4. antibody serology
Histo exam for Coccidiomycosis shows:
spherules containing endospores**
What do the arthroconidia of Coccidiomycosis look like?
thick-walled, barrel-shaped and alternate w/ empty cells

Sporothrix schenckii


aka "Rose Gardener's Disease"
2 forms of Sporothrix and appearance:
1. cigar-shaped yeast (37 C)
2. mold w/ daisy like conidiophores (25 C)
Where is S. schenckii found?

What is it assoc with?**
found in soil

assoc with rose thorns and moss**
Clinical manifestations of Sporothrix? (4)
1. papular skin lesions enlarge and ulcerate
2. firm nodules form along lymphatics
3. multiple ulcers
4. disseminates to bones, lungs, eyes, CNS
2 way to get Sporothrix infection:
1. inhalation of conidia
2. traumatic inoculation of skin
How do you do a lab diagnosis of Sporotrichosis?
culture biopsy: convert mold to yeast phase; no DNA probe
What does Sporothrix look like on culture?
Shape of Sporothrix is described as: