Abstract
BACKGROUND: Sputum culture conversion is an important predictor of treatment response and patient outcome in pulmonary multidrug-resistant or rifampicin-resistant tuberculosis (MDR/RR-TB). However, the determinants of time to culture conversion and its association with treatment regimens among MDR/RR-TB patients in Southwestern Oromia remain poorly understood. This study aimed to determine the time to initial sputum culture conversion and associated factors among pulmonary MDR/RR-TB patients in Southwestern Oromia, Ethiopia. METHODS: We conducted a retrospective follow-up study on 168 MDR/RR-TB patients who had initiated treatment and followed up between 2013 and 2023 at centers in the Southwestern Oromia region of Ethiopia. A semi-structured data collection tool was used to extract demographic, clinical and bacteriological data. The median time to sputum culture conversion was analysed using Kaplan‒Meier survival curves. Bivariate and multivariate Cox proportional hazards regression analyses were employed to identify factors associated with delayed time to sputum culture conversion. A p-value less than 0.05 was considered statistically significant. RESULTS: Of the 168 participants, 85.7% (144) achieved culture conversion during a total follow-up of 397.8 person-months. Among those converted, 48.6% (70/144) achieved conversion within two months, 42.4% (61/144) within three to four months, and 9% (13/144) after four months of treatment. The median time to sputum culture conversion was 62 days (IQR: 32-92). The median time to culture conversion was longer for smear-positive samples (63 days, IQR: 32-93 days) than for smear-negative samples (59 days, IQR: 30-90 days, chi(2) = 6.68, P value = 0.0098). Patients receiving a shorter MDR/RR-TB regimen were twice as likely to achieve culture conversion faster than those receiving longer regimens (aHR = 1.85, 95% CI: 1.11-3.08, P = 0.019). CONCLUSION: The median time to initial sputum culture conversion was 62 days, which was lower than the 4-month threshold considered a potential indicator of treatment failure according to the World Health Organization. MDR/RR-TB patients with HIV coinfection, higher baseline smear grades and those on longer treatment regimens were shown to have a delayed time to culture conversion. Attention should be given to these patients during their MDR/RR-TB treatment course to reduce delays in culture conversion and improve treatment outcomes.