Acquired rifampicin resistance during first TB treatment: magnitude, relative importance, risk factors and keys to control in low-income settings.

Background: The incidence of acquired rifampicin resistance (RIF-ADR; RR) during first-line treatment varies.

Objectives: Compare clinically significant RIF-ADR versus primary and reinfection RR, between regimens (daily versus no rifampicin in the continuation phase; daily versus intermittent rifampicin in the continuation phase) and between rural Bangladesh and Kinshasa, Democratic Republic of Congo.

Methods: From patients with treatment failure, relapse, or lost to follow-up, both the outcome and baseline sputum sample were prospectively collected for sequencing to determine whether RR was present in both samples (primary RR) or only at outcome (RIF-ADR or reinfection RR).