How does drug resistance develop and how is it prevented?

• A. Non-adherence and incomplete therapy drive resistance; prevention includes DOT and completing recommended regimens
• B. Regularly increasing doses prevents resistance
• C. Using only a single drug protects against resistance
• D. Resistance cannot be prevented

Answer: (A)

Drug resistance arises when treatment fails to eliminate every bacterium, so the survivors under drug pressure can acquire or carry mutations that make them less susceptible. In tuberculosis, this is most often driven by not taking medicines as prescribed or stopping therapy before the full course is finished. When doses are missed or therapy ends early, drug levels dip below what’s needed, killing off susceptible bacteria while resistant ones persist and multiply. Over time, the bacterial population becomes resistant.

Prevention hinges on keeping patients on the right medicines for the full duration. Directly observed therapy (DOT) helps ensure each dose is taken as prescribed and the entire course is completed, which minimizes subtherapeutic exposure. Using a combination of several drugs from different classes further reduces the chance that any one bacterium is resistant to all components—if a bacterium is resistant to one drug, the others in the regimen can still kill it. Good monitoring for side effects and potential drug interactions helps people stay on therapy without interruptions. In contrast, increasing doses or relying on a single drug can actually promote resistance, and resistance is not inevitable when proper strategies are used.