Mycobacterium Tuberculosis Features: 1. Acid fast bacteria a. Takes up carbol fuchsin stain b. Contains higher concentration of mycolic acid 2. Cultures very slowly (2-6 weeks) 3. Grows on Lowenstein-Jensen medium 4. Obligate aerobe Transmission: Respiratory droplets Pathogenesis: 1. Lives and resides in macrophages 2. Cell wall contains glycolipids a. These are involved in clumping together of bacteria into serpentine-like formation b. This is called Cord Factor 3. Cord Factor a. It protects the bacteria from being destroyed b. It elicits granuloma formation by increasing following: i. TNF-alpha ii. Other inflammatory cytokines 4. Sulfatides a. Allows bacteria to live inside the macrophage b. It does so by preventing phagolysosome fusion i. Mechanism: sulfatides accumulate in phagosome and create incompetent secondary lysosomes which are unable to fuse. Diseases: There is Primary Pulmonary Infection which leads to following paths of progression: 1. Healed latent infection 2. Systemic infection (Miliary TB) 3. Reactivational TB Primary Pulmonary Infection: 1. It affects lungs (lower and middle lobe) 2. After healing, lesion becomes fibrotic and eventually calcifies along with nearby lymph nodes (Ghon complex) a. Ghon complex are visible calcifications of lung parenchyma and hilar lymph nodes that can be seen on chest X ray i. These present with casseating granulomas Symptoms: 1. Prolonged fever 2. More common in children 3. Most cases resolve by fibrosis and calcification and become latent Systemic TB: 1. Miliary TB 2. Very lethal Reactivational TB: 1. Only occurs in 5-10% of patients 2. Depends on state of immunosuppression 3. Caused due to downregulation of TNF-alpha a. TNF-alpha keeps the TB infection in check in latent period 4. Commonly affects upper lobes of lung Symptoms: 1. 2. 3. 4. Cough Hemoptysis Night sweats Cachexia a. Due to increase in TNF-alpha by cord factor TB can also affect other areas of the body such as: 1. Skeletal system a. Pott’s disease i. TB infects spinal column ii. Involves demineralization of bone with soft tissue swelling 2. CNS a. Occurs in 10-15% of patients b. Meningitis c. Tuberculoma (cavitary lesion) Lab Diagonis: PPD Test. It can be positive in: 1. Latent infection 2. Active infection 3. If patient ever took BCG vaccine Treatment: RIPE 1. 2. 3. 4. Rifampin Isoniazid Pyrazinamide Ethambutol Prevention: 1. Rifampin 2. Isoniazid