What does culture conversion indicate in monitoring TB therapy?

• A. Infection is resolved and treatment can stop
• B. Sputum becomes more viscous
• C. Converts from positive to negative sputum culture indicating treatment response and helps determine infectiousness and duration
• D. The patient develops drug resistance

Answer: (C)

Culture conversion means the sputum culture changes from positive to negative, showing that the detectable viable TB organisms have decreased due to therapy. This is the clearest sign that the patient is responding to treatment and that infectiousness is likely reduced, which is why it helps guide how long therapy should continue and when it may be appropriate to stop. Remember, turning negative doesn’t equal complete cure yet—the full treatment course is still needed to prevent relapse. If cultures stay positive, it prompts a reassessment of adherence, drug levels, or resistance and a possible change in the regimen.