BIOL 134 Lecture Notes - Lecture 27: Mycobacterium, Gram-Positive Bacteria, Tuberculosis
Document Summary
Many members live in water and soil. Two we discuss are obligate parasites; only live in hosts. Resistant to alcohol, drying, most antiseptics and disinfectants. M. tuberculosis = 20 hour generation time. Slow absorption of nutrients through the cell wall. Time from initial infection to symptoms is highly variable. Many who are infected never show symptoms or become ill. If bacterium survives, induces macrophage to attract other macrophages. Phagocytosis of bacterium by a macrophage in the lungs. Usually, bacterium is killed and infection is stopped. As macrophages die, bacteria are released, but grow slowly. As m. tuberculosis spreads, it continues to damage various tissues but. If infection is stopped, tubercles remain as permanent signs of infection. It it progresses, center of tubercle expands: liquefaction particularly the lungs. Patient dies usually from respiratory failure, but other organs can be affected. Skin test: inject m. tuberculosis antigens under the skin. Swelling at site of injection indicates exposure.
