- Caused by Mycobacterium tuberculosis, a slow-growing, acid-fast bacillus (AFB)
- Transmission
- Airborne droplets expelled when an infected person coughs, sneezes, or speaks.
- Microbiology
- Mycobacterium tuberculosis
- Aerobic
- Acid fast bacilli
- Acquired pulmonary infection
- Can disseminate to any organ system
Presentation in General Surgery
- Lymphadenopathy
- GI - peritonitis, ileal, colitis perianal sepsis, fissure, fistula
- Abdo - retroperitoneal mass - renal, adrenal, splenic, liver
- Psoas abscess
- Breast - granulomatous mastitis
Pathology
- Primary
- Mycobacteria inhaled
- Alveolar macrophages phagocytose the bacteria but cannot always kill them due to the bacteria’s ability to inhibit phagosome-lysosome fusion.
- The bacteria replicate intracellularly, triggering an immune response.
- T lymphocytes and macrophages form granulomas to contain the infection, leading to the characteristic caseating necrosis.
- Stages of TB:
- Latent TB: The immune system contains the bacteria, and the infection remains asymptomatic and non-contagious.
- Active TB: Reactivation or progression of the disease occurs when the immune system cannot contain the infection, leading to symptoms.
- Extrapulmonary TB:
- Bacteria can spread hematogenously, causing TB in other organs like lymph nodes, bones (Pott’s disease), CNS (meningitis), or genitourinary system.
Investigations
- Gram stain - Acid Fast bacillus
- Microbial culture takes 6 weeks
- Mantoux
- Interferon-Gamma Release Assays (IGRAs): Blood tests (e.g., QuantiFERON-TB Gold)
- CXR
Management
- Rifampicin for 4 months - others are isoniazid, pyrazinamide and ethambutol
- Prevention - BCG vaccination