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19 Cards in this Set

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CRYPTOCOCCUS NEOFORMANS

clinical significance:
important opp.path. in AIDS, an "AIDS defining illness"

Requires life-long therapy
Structure:

Location:
ONLY pathogenic fungus with a capsule

First ID'd in peach juice, major contaminants = soil contam with pigeon droppings, eukalyptus trees, decaying wood-forming hollows in living trees
Growth form:

Staining:
Yeast (in agar and clinical specimens)

Stains poorly with gram and others, requires special fungal stain
Virulence factors:

Growth Characteristics:
1) MAJOR one = GXM capsule (glucuronoxylamannan) - 4 serotypes
2) Melanin - has phenol oxidases which use dopamine to create melanin

grows at 37C, Urease +
Route of transmission:

Most common disease:

Most common disseminated sites:
Most common = inhaled spores or dessicated yeast forms

chronic meningitis

bone and skin
Location:

Diagnosis:

Stain:
world-wide, ubiquitous
associated with bird droppings and vegetation

Detect capsular Ag with latex beads that have anti-capsular Ab's

Capsule stains red with mucicarmine
Prevention:

Treatment:
promising research on capsular vaccine (conjugated to tetanus toxoid)

amphotericin B, and flucytosine (synergistic)
HEMATOGENOUSLY DISSEMINATED DISEASE caused by C. ALBICANS

Clinical significance:

Can lead to what infection?
hospital bloodstream infections - 4th most common cause

Internal candidiasis of any tissue
Lab ID:

Treatment
positive blood cultures = infection BUT may be negative even though abscesses are present on internal organs

Internal infections: Amphotericin B, binds ergosterol
Internal and mucosal infections: Azoles, inhibit ergosterol synth enzymes
ASPERGILLUS

Clinical significance:

Growth form:
once established in tissue, organisms spread rapidly and penetrate tissue barriers
High risk for systemic disease - neutropenic and immunosuppressed hospitalized pts

A. fumigatus and flavus grow in mycelial forms only (mold)
Cultures - form septate aerial hyphae, stalk-like conidiophores with easily airborne conidiospores
Infections

Hypersensitivity pneumonitis:
Secondary Colonization:
Systemic aspergillosis:
allergic bronchopulmonary reactions to fungal Ags -> respiratory distress

pre-existing cavitary lesions in lungs become colonizes - space filled with sperical intertwined, branching, septate hyphal filaments -> minimal distress except hemoptysis

aggressive invasion of blood vessels and tissues, important risk factor = neutropenia
Location:
ubiquitous in environment especially air
Contamination of air conditioner filters may occur
NOT normal human flora, but there may be transient colonization
Diagnosis:
Treatment:
Culture bronchial washes, tissue, or sputum
use histological staining look for - septate hyphae branching at regular intervals, oriented in same direction, acute angle branching

Amphotericin B
Other mycelial form opportunistic fungi:
Zygomycetes (coenocytic, not septate) causes zygomycoses
Mucor causes Mucormycosis
Pneumocystis causes Phycomycosis
Pneumocystis carinii
aka:

Clinical significance:
P. jiroveci (new name)

common with AIDS pt's CD4 count < 200 cells/mm3
subclinical pulmonary infections occur worldwide in animals (but each animal has its own type of P. carinii)
Specific antibodies in all children by 4 years
Culture:

Atypical characteristics for fungi:
human forms can't be cultured or grown in animals!

1) morphology: similar to phylum Apicomplexa (cysts and trophozoites), relative fragility of cell wall
2) Susceptible to some anti-parasitic agents like pentamidine, trimethoprim/sulfamethoxazole
3) not suscept to Amphotericin B
4) No ergosterol, presence of cholesterol
Evidence for fungal classification:
rDNA, presence of EF3 (only in fungi), thymidylate synthase and dihydrofolate reductase on two separate genes (seen in fungi), cell wall chitin, glucan and mannoproteins
Pathogenesis:
Forms cysts containing sporozoites, released when cyst ruptures -> mature to trophozoites
Limits Oxygen uptake -> asphyxiation, require oxygen therapy
Interstitial pneumonitis with plasma cell infiltrates and distinctive foamy alveoli
Transmission:

Prevention:

treatment:
HIGHLY contageous
Source is unknown, believed to be airborne person to person

keep immunosuppressed pts away from infected pts

antifungal therapy