Tuberculosis

Tuberculosis

1. Microbiology

   • Classification
     • MTC - Mycobacteria tuberculosis complex
       • M. tuberculosis
       • M. bovis
       • M. africanum
     • MOTT - Mycobacteria other than tuberculosis
       • M. avium
       • M. intracellulare
       • M. scrofulaceum
       • M. xenopi
       • M. leprae
   • Characteristics of M. Tuberculosis
     • Long, slender, straight bacilli
     • Intracellular bacteria
     • Obligate aerobes
     • Cell wall contains mycolic acids
       • Poorly gram stains
       • Requires special acid fast stain
         • Ziehl Neelsen stain
     • Grows on Lowenstein Jensen Agar

2. Risk factors

   • Immunosuppression (E.g.: HIV)
   • Chronic diseases
   • Subtance abuse
   • Malnutrition
   • Geography
     • Sub-saharan africa

3. Signs and symptoms

   • Fever/chills
     • Pathophysiology
       • 1- Exogenous pyrogens activate immune cells
       • 2- Production of endogenous pyrogens
         • IL-1
         • IL-6
         • TNF-a
       • 3- Pyrogens activate the anterior hypothalamus (via prostaglandin E2)
       • 4- Increased thermoregulatory set point
         • FEVER
   • Night sweats
   • Primary TB is asymptomatic
   • Weight loss
   • Cough with hemoptysis
   • Loss of appetite
   • Chest pain
   • Pleural effusion
     • Types
       • Exudative
         • Caused by inflammation and increased capillary permeability
         • Causes
           • Infections (pneumonia, TB)
           • Malignancy
           • Connective tissue disease
       • Transudative
         • Caused by increased hydrostatic pressure or decreased oncotic pressure
         • Causes
           • CHF
           • Cirrhosis
           • Nephrotic syndrome

4. Investigations

   • Active TB
     • Labs
       • Sputum
         • Acid fast staining
         • Mycobacterial culture
           • GOLD STANDARD
       • Blood
         • PCR testing
         • HIV serology
     • Radiology
       • Chest X-ray
         • Cavity formation
           • Classic hallmark
         • Hilar lymphadenopathy
         • Ghon complex
           • Calcified nodule representing a caseating granuloma
         • Consolidation
         • Pleural effusion
   • Latent TB
     • Skin tuberculin test (TST) using purified protein derivative (PPD)
       • Indications
         • High risk TB exposure
           • E.g.: Close contacts
         • High risk TB reactivation
           • E.g.: HIV patients
       • Tests for the presence of cell mediated immunity against M. Tuberculosis
       • Procedure
         • 1- Intradermal injection of PPD on ventral surface of forearm
         • 2- Measure transverse diameter of palpable lesion after 48-72 hours
       • Interpretation

5. Management

   • First line drugs
     • RIPE
       • Rifampin
         • Given in 2 month intensive phase + 4 months continuation phase
       • Isoniazid
       • Pyrazinamide
         • Given in 2 month intensive phae only
       • Ethambutol
   • Second line drugs
     • Aminoglycosides
     • Bedaquiline
     • Fluoroquinolones
     • Para-aminosalicylate (PAS)
     • Ethionamide
     • Cycloserine
     • Macrolides
     • Capreomycin

6. Complications

   • Pulmonary
     • Acute respiratory distress syndrome
     • Massive hemoptysis
     • Pneumothorax
     • Bronchiectasis
     • Lung cancer
     • Venous thromboembolism
   • Extrapulmonary
     • Intestinal TB
       • Intestinal hemorrhage, obstruction, and perforation
     • Genitourinary TB
       • Pyelonephritis
     • TB pericarditis
       • Can lead to HF
     • TB meningitis
     • Pott disease
       • Infection of lumbar vertebrae

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