How can stopping tuberculosis treatment early lead to drug-resistant bacteria?

Stopping tuberculosis treatment early or failing to follow the prescribed regimen allows surviving bacilli to multiply and develop resistance to the medications being used.12

When a patient does not complete the full course of therapy, the most sensitive bacteria are killed, but the more resistant organisms may survive and continue to replicate. If treatment is interrupted or involves only a single drug, these surviving bacilli can become resistant to that specific agent. If subsequent treatment remains incomplete, the bacteria can develop resistance to multiple drugs, leading to multidrug-resistant tuberculosis (MDR-TB), which is significantly harder to cure and often requires longer, more aggressive therapy with drugs that may have more severe side effects.314

To prevent this, it is ethically imperative for patients to adhere to their full treatment regimen as prescribed. Programs like directly observed therapy (DOT) are often implemented to ensure compliance and prevent the emergence of these dangerous, resistant strains.31