Why so many drugs for so long?
Treating active TB is not like a one-week course of antibiotics for a sore throat. The standard cure uses four drugs together for an intensive phase, then two drugs for several more months — usually six months in total. The classic first-line combination is isoniazid, rifampicin, pyrazinamide, and ethambutol. Why this elaborate approach?
- Several drugs at once: in any large TB population a few bacteria are naturally resistant to one drug. Using several drugs together means each bug faces an attack it cannot dodge.
- Many months: TB includes slow, semi-dormant bacteria hidden in granulomas. They are killed only gradually, so a long course is needed to clear the last survivors.
- Finishing the course: most people feel well within weeks, long before the bugs are gone. Stopping early is the classic mistake that lets resistant survivors regrow.
Drug resistance and directly observed therapy
When treatment is interrupted, taken irregularly, or uses too few drugs, the susceptible bacteria die but the tougher, resistant ones survive and multiply. Over time this breeds multidrug-resistant TB (MDR-TB) — strains resistant to the two most important first-line drugs. MDR-TB is far harder, longer, and costlier to cure, requiring second-line drugs with more side effects. Resistance is, in large part, a human-made problem of incomplete treatment.
To keep treatment on track, public-health programmes use directly observed therapy (DOT): a health worker or trained supporter watches the patient swallow each dose. It sounds simple, but it dramatically improves completion rates, protects the patient, and shields the community from resistant strains. Rapid tests like GeneXpert help here too, by flagging resistance early so the right drugs are chosen from the start.
The cousins: non-tuberculous mycobacteria
TB is not the only mycobacterium that affects the lungs. The non-tuberculous mycobacteria (NTM) are a large family of related bugs that live in soil, water, and household plumbing. They are everywhere in the environment, and — importantly — they are generally not spread person to person, unlike TB.
Most healthy people breathe NTM in and out without any trouble. But NTM can cause slow, chronic lung infection in people with already-damaged lungs — for example those with bronchiectasis or long-standing airway disease. Because NTM are acid-fast just like TB, a positive smear cannot tell them apart; this is one reason molecular and culture identification matters. Finding NTM in sputum does not automatically mean disease — doctors must weigh symptoms, scans, and repeated samples before treating.