What does culture conversion indicate in TB therapy?

• A. Worsening cough
• B. The shift from positive to negative sputum culture
• C. No change in culture
• D. Increased sputum culture growth

Answer: (B)

Culture conversion means the sputum culture shifts from positive to negative, indicating the bacteria are no longer growing in the culture. This shows the patient is responding to anti-TB therapy, with a reduced bacterial load to undetectable levels and typically a lower risk of contagiousness. It’s a key signal of bacteriologic improvement and helps clinicians gauge progress, timing of isolation, and overall treatment trajectory. Keep in mind, conversion is a favorable sign but not a guaranteed cure—ongoing monitoring, adherence, and sometimes further testing are needed, as some patients may relapse even after initial conversion.