pulmonary tuberculosis

a disease caused by mycobacterium TB typically affects the lungs

MYCOBACTERIUM TB

called mycobacterium because it contains a substance called myolic acid, which contains lipids, making the cell wall a lipid-rich cell wall.

Mycobacterium are acid fast because they are resistant to decolorization by acid after stain, so they Gram stain poorly; instead, a ziehl stain is used. It is obligate aerobic bacillus, meaning it requires oxygen to grow

mycobacterium virulence factors

has a cord factor which helps TB evade immune response, causing granuloma formation and trigger cytokine release .

TB also has sulfatides, which are glycolipids on the surface of mycobacteria and they prevent phagocytic activation for the survival of the bacteria inside cells

TB also has a catalase peroxidase enzyme, which allows TB to be resistant to host cell oxidation

PATHOPHYSIOLOGY

PRIMARY INFECTION

1.Inhaled TB bacteria through inhaled aerosolized droplets, and reside in the lower/mid lobes of the lungs

2.alveolar macrophages tries to phagocytose it and becomes infected and becomes activated and release cytokines (TNF-A, IL-8, IL-6) recruiting neutrophils , T lymphocytes, and monocytes to the site of infection

3.infected macrophages go the thoracic lymph nodes and proliferate within the thoracic nodes forming HILAR LYMPHEDENOPATHIES

  1. recruited macrophages also become infected after trying to phagocytose the bacteria and form a granuloma and isolate the bacteria to that area, forming Ghon-focus

    *HILAR LYMPHEDENOPATHY+GRANULOMA=GHON COMPLEX

  2. infected macrophages present the antigen through MHC-2 to naive T- helper cell and release IL-12 which turns T-helper cell 1

  3. T-helper cell 1 will release IFN-Y which fully activates macrophages to more effectively destroy the bacteria lysosomal enzyme action and the bacilli that are strong enough survive and remain dormant inside the granuloma until a secondary infection


    Symptoms of Active TB include:

    • Weight loss

    • Fatigue

    • Productive and persistent cough, hemoptysis

    • Fever

    • Night sweats


      Physical assessment findings and lab results for Active TB:

      • Dullness to chest percussion

      • Rales

      • Increased vocal fremitus

      • Moderate elevation in white blood cells with predominant lymphocytes

      • Positive sputum specimens for acid-fast bacilli

      • Chest radiograph may show patchy or nodular infiltrates in apical of upper lobes or superior of lower lobes, and may show cavitation as infection progresses


    Factors that make a Mantoux test positive for TB:

  • Positive if ≥5 mm in HIV+

  • Positive if ≥10 mm in immigrants from high-prevalence countries

  • Positive if ≥15 mm in individuals with no known risk factors for TB, recent contact with TB case, intravenous drug users, nodular or fibrotic changes on chest X-ray, high-risk settings, organ transplant or other immunocompromised patients, mycobacterial lab personnel, high-risk comorbidities, and children <4 or any child exposed to high-risk adults