Chapter 14: Mycobacterium
Terms
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- What are the two species of mycobacterium?
- Mycobacterium tuberculosis and Mycobacterium leprae
- What are the two acid-fast staining bugs?
- Mycobacteria and Nocardia
- Mycobacteria - aerobes or anaerobes?
- Obligate aerobes
- Growth and pathogenesis of Mycobacterium tuberculosis?
- Facultative intracellular growth - allows the bacteria to cruise through the lymphatics and blood. Eventual macrophage attack results in local destruction of tissue and caseous necrosis.
- PPD? what does it detect?
- Purified Protein Derivative. Detects whether a person has been exposed to/infected with tuberculosis, NOT necessarily active tuberculosis.
- Describe primary tuberculosis? Transmission
- Usually a subclinical lung infection. Transmitted via aerosolized droplet nuclei, which land in the middle and lower lung zones. Cell-mediated immunity walls off and suppresses the bacteria, which lie dormant.
- Describe secondary tuberculosis? aka?
-
Aka reactivation TB. Infection can occur in any organ system seeded during the primary infection.
1. Pulmonary - most coomon
2. Pleural, pericardial infection
3. Lymph node infection
4. Kidney
5. Skeletal
6. Chronic arthritis of a joint
7. Subacute meningitis
8. Miliary tuberculosis - What is a Ghon focus?
- A calcified tubercle in the middle or lower lung zone.
- What is a Ghon complex?
- A Ghon focus accompanied by perihilar lymph node calcified granulomas.
- What is the general presentation of TB?
- Chronic - weight loss, low-grade fever, symptoms related to the organ system infected. Often confused with cancer; one of the great imitators.
- How can TB be diagnosed?
- PPD skin test, chest Xray, and sputum acid-fast stain and culture.
- What is the lifetime reactivation risk in patients exposed to TB? What is the ANNUAL reactivation risk in HIV patients?
- 10% for both.
- What is Mycobacterium avium-intracellulare?
- Usually only affects birds and other animals - but infects up to 50% of AIDS patients.
- Leprosy involves which parts of the body?
- The cooler areas - skin (except the armpit, grouin and perineum), the superficial nerves, eyes, nose, and testes.
- What is the severest form of leprosy? Manifestations?
- Lepromatous leprosy (LL) - no cell-mediated immune response can be mounted. Leonine facies (lion face), saddlenose deformity, internal testicular damage, loss of sensation in glove and stocking distribution.
- What is tuberculoid leprosy?
- Patients can mount a cell-mediated defense - milder and often self-limiting disease.
- How is leprosy tested for?
- Lepromin skin test - measures the ability of the host to mount a delayed hypersensitivity reaction against antigens of Mycobacterium leprae.