Mycobacterium tuberculosis

Tubercle

Distinctive granulomatous lesion formed in tissues in response to infection with Mycobacterium tuberculosis

Mycobacterium tuberculosis

Slow-growing, rod-shaped, acid-fast bacterium; causative agent of human tuberculosis

Mycolic acid

Waxy lipid forming the major component of the mycobacterial cell wall; confers resistance to chemicals, impairs antibiotic uptake, and contributes to virulence

Acid-fast stain / Ziehl-Neelsen stain

Special staining method used to identify mycobacteria; retains stain due to mycolic acid-rich cell wall

Obligate intracellular pathogen

Organism that can only survive and replicate within host cells; M. tuberculosis persists inside macrophages

Cord factor

Glycolipid in the mycobacterial cell wall; causes growth in serpentine cords; toxic to host cells; linked to virulence

Antigen 85 complex

Surface proteins that bind host fibronectin; facilitate adhesion and may contribute to tubercle formation

Ghon focus

Initial granulomatous lesion formed in the lung after primary infection; site where bacteria may remain dormant/latent

Latent TB infection

State where M. tuberculosis is present but inactive; no symptoms; not infectious; tuberculin test positive; chest X-ray normal; may reactivate later

Primary TB

Initial infection following inhalation of airborne droplets; often asymptomatic or mild; cell-mediated immunity develops; granulomas form

Post-primary / Reactivation TB

Disease arising from reactivation of dormant infection when immunity weakens; granulomas rupture; lung cavitation occurs; infectious with symptoms

Miliary / Disseminated TB

Widespread infection where bacteria spread via the bloodstream; affects many organs; can be life-threatening; common in immunocompromised individuals

Pott’s disease

Tuberculosis affecting the spine; causes vertebral damage and deformity

Tuberculin / Mantoux test

Skin test measuring delayed-type hypersensitivity to TB proteins; induration size indicates exposure

Interferon-gamma release assay (IGRA)

Blood test measuring T-cell response to TB antigens; confirms infection

BCG vaccine

Live attenuated Mycobacterium bovis vaccine; provides partial protection against TB; not lifelong efficacy; targeted at high-risk groups

Rifampicin

First-line anti-TB drug; inhibits RNA synthesis

Isoniazid

First-line anti-TB drug; inhibits mycolic acid synthesis

Ethambutol

First-line anti-TB drug; disrupts cell wall arabinogalactan synthesis

Pyrazinamide

First-line anti-TB drug; disrupts cell membrane function and energy metabolism

Multi-drug resistant TB (MDR-TB)

TB resistant to both rifampicin and isoniazid; requires prolonged treatment with second-line drugs

Extensively drug-resistant TB (XDR-TB)

TB resistant to first-line drugs plus key second-line agents; difficult to treat; lower success rate

DOTS (Directly Observed Therapy, Short-course)

Treatment strategy where healthcare workers observe medication intake; ensures adherence; used for MDR-TB or poor compliance

Notifiable disease

Disease legally required to be reported to public health authorities upon diagnosis; TB is notifiable in the UK