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25 Cards in this Set
- Front
- Back
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What are the 3 major types of mycobacteria?
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1. Mycobacterium tuberculosis - causes TB
2. Nontuberculous Mycobacteriam (slow and rapid growers) - causes pulmonary/cutaneous infection 3. Mycobacterium leprae - causes leprosy |
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What are characteristics of mycobacteria?
Gram +/- Rate of replication |
NEITHER - have mycolic acid cell envelope (lipid/waxy) which does NOT gram stain
- Only stained by acid-fast stains - Obligate Aerobes - Slow rate of replication |
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What type of infection does Mycobacterium tuberculosis cause?
What type of pathogen? |
- INTRACELLULAR pathogen
- Triggers granulomatous inflammation - Because intracellular pathogen, cell-mediated immunity required to control infection - Latent infection often seen in immunocompromised (especially in CD4+) patients |
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Is tuberculosis an old or new disease?
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ANCIENT, seen in mummies
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How is TB transmitted?
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- Airborne transmission by inhalation of aerosol droplet nuclei
- Can remain airborne for hours |
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What is the worldwide burden of TB?
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- 2 billion worldwide infected
- 2 million deaths / year |
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What are the 3 stages of TB infection?
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1. Primary infection - aerosol deposition into lungs. Infection of macrophages, travels to lymph nodes
2. Latency - controlled primary infection w/ o disease. Not contagious. 3. Reactivation - Occurs after initial control. High risk of occuring in AIDs patients. |
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Where is the most common site of reactivation of TB?
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Apices of the lungs
- Necrosis causes cavities with high densities of mycobacteria |
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What are 5 extrapulmonary manifestations of TB?
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1. Meningitis
2. GI Infection 3. Lymphadentitis 4. Genitourinary Disease 5. Skeletal TB |
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How is TB tested/diagnosed?
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Most Common - Tuberculin Skin Test (TST). Tests for delayed type hypersensitivity reaction to M. tuberculosis antigens.
- Can get false positives and negative. Not perfect test. IFN-Gamma Release Assay - measures immune response to 2 small, immungenic M. tuberculosis peptides - Better, but might not show positive w/ patients of weakened immunity |
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How is Mycobacterium tuberculosis treated?
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- With Directly Observed Therapy (DOT)
- Multi-drug regimens for 6 months to over a year Drugs: 1. Isoniazid 2. Rifampin 3. Pyrazinamide 4. Ethambutol |
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What is Isoniazid (INH) and what are its side effects?
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TB Treatment
- Inhibits mycolic acid synthesis - Hepatitis and Peripheral Neuropathy |
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What is Rifampin and what are its side effects?
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- Inhibits RNA Polymerase
- Turns urine orange and Hepatitis |
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What is Pyrazinamide (PZA) and what are its side effects?
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- Targets 30s ribosome subunit
- Hepatitis |
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What is Ethambutol (EMB) and what are its side effects?
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Drug for TB
- Inhibits syntheisis of cell wall arabinogalactan - Does NOT cause hepatitis - Causes Retrobulbar neuritis (decreased red-green color discrimination) |
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For a TB strain to be classified as MDR (multi-drug resistant), what does it have to be resistant to?
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Resistant to BOTH INH and Rifampin
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Is there a TB vaccine?
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Yes (BCG), which is a live-attenuated vaccine, but provides rather limited protection against TB
- Not given in US, but is routine in many other countries |
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What 2 categories are Nontuberculous Mycobacteria classified into?
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1. Slow Growers
2. Fast Growers |
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Where is Nontuberculous Mycobacteria found?
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Very prevelent in environment
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What can Nontuberculous Mycobacteria cause?
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1. Pulmonary Disease - M. avium and M. kansasii
2. Cutaneous Infections - M. marinum and M. ulcerums |
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What animal does Mycobacteria leprae colonize?
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Armadillos
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What environment does Mycobacteria leprae prefer?
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- Replicates in skin
- Prefers COOLER environemnt |
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How is M. leprae transmitted?
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Spread by nasal secretion, respiratory droplets
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What does M. leprae cause?
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Leprosy - infiltrative nerve lesions, peripheral sensory nerve damage
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How is M. leprae treated?
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Prolonged multi-drug regimen of:
1. Rifampicin 2. Dapsone 3. Clofazimine |
