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TB and Fungal Infections


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Define TB
-chronic pneumonia
- characterized by caseous necrosis and granuloma formation
Which is the most important agent causing TB?
- M. tuberculosis is the most important (no reservior except man)
What are some important biologic properties?
1. Obligate aerobe: grows best where pO2 is high, i.e. lung apex
2. High cell-wall lipid content (Acid Fast orgs)
3. Slow growing (18 hrs cellular division)
Who are high risk for TB?
Blacks, Hispanics, extremes of age, pregnant, immigrant, diabetics, alcoholics, drug addicts
How is TB acquired?
TB acquired via person-to-person transmission via aerosol route
- deposition of "droplet nuclei" in lung
What is the sequence of infection w/ TB?
transmission->droplet nuclei deposition in lung->inadeq host defenses->primary infection->latent->secondary or reactivation TB
What are the 2 broad categoies used for TB and what are the characteristics?
1. Primary (childhood) TB= atypical, pleurisy or effusion, extra-pulm TB

2. Reactivation TB (3 syndromes present)= asymptomatic, chronic upper lobe dx, or fever of unknown origin
What is the problem with TB diagnosis?
TB can look like many other diseases.
Lung cancer, bacterial pneumonia, lung abscess, lymphoma, other cancers and fungal disease
How does one diagnose TB?
- Presumptive diagnosis made w/ stained smears.
- Diagnosis is confirmed when organism is grown
How does one treat TB?
1. Combination of drugs to prevent resistance
2. Prolonged therapy (6-18 months): to eradicate persistent organisms
3. Supervised therapy
How does one prevent TB infection?
1. BCG immunization
2. pt. identification & isolation
3. (-) pressure room in hospital
What are the 8 features of endemic fungal infection?
1. Soil organisms
2. Specific geographic pattern (endemic areas)
3. Airborne spores are the infecting agent and the lung is the portal of entry
4. Primary infections are asymptomatic or mild - "flu" like. (resolve without
treatment- analogous to TB).
5. Disseminated disease
a. Rare
b. Occurs in debilitated or immune compromised hosts
6. Chronic pulmonary forms of most fungal infections exist and they are cavitary
7. Diagnosis by culture of histo
8 tx = amphotericin B

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