TB Flashcards
TB
Infectious disease of the respiratory tract. Often spreads to other organs.
Granuloma with central caseous (cheesy) necrosis.
It is engulfed by alveolar macrophages in alveoli.
People can be exposed to TB but not get any symptoms
Common locations of pulmonary TB
Lung apices (high V/Q ratio)
Cavity formation
Granulomas
Clinical presentation
Gradual onset Malaise Weight loss Night sweats, rigors Fever Cough Haemoptysis Breathlessness Chest pain Headaches Drowsy Fits
Clinical signs
Palpation: Lymphadenopathy
Percussion: Upper zone crackles
Auscultation: Bronchial breath sounds
Cardiac tamponade
Investigations
Sputum microscopy - AAFB, ZN stain (mycobacterium waxy coat retains the red stain even after exposure to acid and alcohol)
PCR - Diagnostic test for TB. Get the genetic material. Results available quickly, limited species information.
CXR - look for abnormalities especially cavities in the upper lobes
Culture - Slow process, requires specialised media.
Causative organisms
Mycobacterium Tuberculosis
Mycobacterium Bovis
Primary TB
First TB exposure and up to 5 years afterwards
Inhaled organism phagocytosed and carried to hilar lymph nodes (large hilar lymph nodes)
Granulomatous formation
Small Ghon focus in periphery of mid zone of lung
Secondary TB
Re-infection/Re-activation of TB in a person with some immunity.
Management
6 month long treatment - bacteria slowly die and could reactivate TB if treatment is stopped early
2 RIPE 4 RI
2 months
Rifampicin - colours all body fluids orange
Isoniazid - Hepatitis, neuropathies
Pyrazinamide - Hepatitis, joint pains, arthralgia
Ethambutol - colour blind, optic neurosis
4 months
Rifampicin
Isoniazid
Drug resistance in TB
single agent - isoniazid (give a prolonged course of drugs instead)
Risk factors
HIV
Route of infection spread
Airborne
Miliary TB
Spread in the blood
Life threatening
Spreads everywhere
CXR findings - miliary nodules, lots of cavities and opacities over both lungs
Latent TB
Can’t spread infection to others.
Bacteria can ‘wake up’ at any time and make patient ill with active TB.
Diagnosis of latent TB
IGRA blood test - detects any previous exposure to TB.
Mantoux test - skin test. Detects previous exposure to Tb and BCG. +ve result = TB bacteria present in body
-ve result = no TB bacteria present in body
