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56 Cards in this Set
- Front
- Back
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***Cryptococcosis***
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***Cryptococcosis***
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What is the only encapsulated yeast:
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Cryptococcus neoformans has a polysaccharide capsule
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Where do people get Cryptococcus neoformans?
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Pigeon droppings and soil
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Who gets disease from Cryptococcus?
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Normal and IC hosts
7-8% of AIDS pts |
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Most common predisposing factor for Cryptococcus in non-AIDs patients:
Other predisposing factors: |
Large doses of adrenal corticosteroids
Sarcoidosis and lymphoma |
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How do you acquire Cryptococcus infection?
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Inhalation into lungs (no case clustering)
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Cryptococcus infections in immunocompetent patients are:
Pulmonary infections may be: |
Self-limited
Symp or asymp |
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What is the major infection of concern with Cryptococcus and how does it occur?
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Hematogenous spread to CNS occurs even w/ subclinical infections
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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) |
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How do most people w/ Cryptococcus present?
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Meningoencephalitis: HA, nausea, gait problems, dementia, irritability, cranial nerve problems and hydrocephalus, mild fever and nuchal rigidity
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What happens to people who go untreated for Cryptococcus?
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Deepening coma if untreated → death
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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 |
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What occurs w/ disseminated Cryptococcus infections?
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Raised skin lesions in immunocompromised pts
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Cryptococcus virulence factors (3):
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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) |
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Lab diagnosis - Cryptococcus on culture:
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Distinctive brown colonies
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For rapid diagnosis of Cryptococcus:
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India Ink stain shows large white capsule surrounding the yeast
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What is the best test for picking up Cryptococcus? Uses?
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Cryptococcal Antigen Latex Agglutination test
Detects antigen in CSF and serum; best for patients w/ cryptococcal meningitis |
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What histopathological methods are used for Cryptococcus? (3)
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1. PAS/GMS – stains the cell body but not the capsule
2. Mucicarmine – stains capsular material 3. Methenamine silver (GMS) stain |
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What is Cryptococcus potential confused for and what test does not allow for this confusion?
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Coccidiodes immitis; use Mucicarmine stain
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***Histoplasmosis***
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***Histoplasmosis***
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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 |
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Does H. capsulatum have a capsule?
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NO!
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Where is H. capsulatum found and in what region of the country?
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Soil, bird, and bat droppings
Ohio/Mississippi River Valleys (Chicago is on fringe of endemic area) |
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3 ways that Histoplasmosis may present clinically?
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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 |
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What is the hallmark of H. capsulatum?**
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Infection of RE by yeasts growing in macrophages**
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Where can Histoplasma yeast spread?
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Liver, spleen, bone marrow*
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Primary lesion of Histoplasmosis?
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Granuloma in lung (do sputum sample)
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3 ways to diagnose Histoplasmosis?
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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 |
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What does Histoplasmosis look like histologically?
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Intracellular yeast form in multinucleate giant cell
Looks like they have capsules, but they do not |
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What techniques can be used to diagnose Histoplasmosis?
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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) |
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***Blastomycosis***
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***Blastomycosis***
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**Major characteristic of Blastomyces dermatitides?**
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broad-based budding**
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Where is Blasto found and what is it associated with?
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central U.S.
in soil and wood |
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Other name for Blastomycosis?
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Chicago disease
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What animal other than humans can be infected by Blasto?
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dogs: they tell you that Blasto is in an area
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Clinical manifestations of Blasto? (4)
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1. pulmonary
2. skin lesions 3. lytic bone lesions 4. disseminated disease |
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2 types of pneumonia seen with Blasto infections?
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1. acute self-limited: resolves in one month
2. chronic pneumo: progressive course, abnormal chest X-ray in 2/3 |
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What may skin lesions due to Blasto progress to?
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large ulcers
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What histological stains can be used for Blasto and what is seen?
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stains: GMS, PAS
large, broad-based budding yeast are observed |
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Lab diagnosis of Blasto:
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1. broad-based budding yeast on KOH prep (BBB!)
2. septate hyphae and unbranched short conidiophores ("lollipop shaped") |
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***Coccidioidomycosis***
(Coccidiodes immitis) aka? |
***Coccidioidomycosis***
"San Joaquin Valley Fever" "Desert Rheumatism" |
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What does Coccidiodes immitis look like:
in tissue? in culture? |
tissue: spherule filled w/ endospores
culture: mold* w/ barrel-shaped arthroconidia |
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Is Coccidioides transmitted person-to-person?
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no!
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Pathogenesis of Coccidioides?
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inhale arthroconidia --> into alveoli --? monocytes ingest arthroconidia --> they become spherules
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Clinical manifestations of Coccidiomycosis?
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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 |
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4 methods of lab diagnosis for Coccidiomycosis:
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1. micro exam: detects spherules*
2. culture: alternating arthroconidia; DNA probe of colony 3. positive skin test (1-4 weeks) 4. antibody serology |
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Histo exam for Coccidiomycosis shows:
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spherules containing endospores**
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What do the arthroconidia of Coccidiomycosis look like?
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thick-walled, barrel-shaped and alternate w/ empty cells
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***Sporotrichosis***
Sporothrix schenckii aka? |
***Sporotrichosis***
aka "Rose Gardener's Disease" |
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2 forms of Sporothrix and appearance:
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1. cigar-shaped yeast (37 C)
2. mold w/ daisy like conidiophores (25 C) |
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Where is S. schenckii found?
What is it assoc with?** |
found in soil
assoc with rose thorns and moss** |
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Clinical manifestations of Sporothrix? (4)
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1. papular skin lesions enlarge and ulcerate
2. firm nodules form along lymphatics 3. multiple ulcers 4. disseminates to bones, lungs, eyes, CNS |
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2 way to get Sporothrix infection:
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1. inhalation of conidia
2. traumatic inoculation of skin |
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How do you do a lab diagnosis of Sporotrichosis?
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culture biopsy: convert mold to yeast phase; no DNA probe
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What does Sporothrix look like on culture?
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rosette-formation/clusters*
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Shape of Sporothrix is described as:
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cigar-bodies
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