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Treatment outcomes for multidrug/rifampicin-resistant tuberculosis (MDR/RR-TB) and extensively drug-resistant tuberculosis (XDR-TB) remain poor across the globe and in the Russian Federation. Treatment of XDR-TB is challenging for programmes and patients often resulting in low success rates and onward transmission of drug-resistant strains. Analysis of factors affecting culture conversion rate among XDR-TB patients may serve as a basis for optimization of treatment regimens. We conducted a retrospective cohort study using health records from 54 patients with pulmonary XDR-TB treated at a tertiary level facility in the Russian Federation. The study population included adult patients with culture-positive pulmonary XDR-TB who started treatment between 1 January 2018-30 June 2019. Culture conversion was defined as two consecutive negative cultures, collected at least 30 days apart. The date of sputum culture conversion was taken from the first of two consecutive negative sputum cultures fulfilling these criteria. We measured time to culture conversion using cumulative incidence functions accounting for competing risks and applied binary cause-specific Cox regressions to assess associated factors. Sputum culture conversion was recorded for 43 (79.6%) patients. Median time to culture conversion adjusted for competing risk of loss to follow up was 4 months [95% confidence interval (CI): 2-5]. The number of patients who had culture converted by treatment months 2, 4, and 6 were 12 (22%), 29 (54%) and 38 (70%) respectively. In unadjusted analysis, positive baseline sputum smear microscopy [hazard ratio (HR): 0.34, 95% CI: 0.18-0.66; p=0.001), hepatitis C (HR: 0.35, 95% CI: 0.14-0.89; p=0.023], and human immunodeficiency virus (HR: 0.30 95%, CI: 0.09-0.97; p=0.045), and receipt of fewer than 4 effective drugs in the treatment regimen (HR: 0.13, 95% CI: 0.03-0.60; p=0.009) were associated with delayed culture conversion. When compared to their combined use, patients receiving regimens with bedaquiline only (HR: 0.12, 95% CI: 0.03-0.49; p=0.003) or linezolid only (HR: 0.21, 95% CI: 0.06-0.69; p=0.010) were less likely to achieve timely culture conversion. Factors delaying sputum culture conversion should be considered in the management of patients with XDR-TB and considered by clinicians for regimen design and treatment strategies. Our study outlines the importance of simultaneous inclusion of bedaquiline and linezolid in treatment regimens for patients with XDR-TB to reduce time to sputum conversion and increase treatment success. [ABSTRACT FROM AUTHOR]

In this retrospective cohort study of patients treated for multidrug-resistant tuberculosis in the Russian Federation, we found that monthly exposure to an aggressive multidrug-resistant tuberculosis regimen was a robust predictor of decreased risk of death or failure during treatment.Background. Evidence is sparse regarding the optimal construction of regimens to treat multidrug-resistant (MDR) tuberculosis disease due to strains of Mycobacterium tuberculosis resistant to at least both isoniazid and rifampin. Given the low potency of many second-line antituberculous drugs, we hypothesized that an aggressive regimen of at least 5 likely effective drugs during the intensive phase, including a fluoroquinolone and a parenteral agent, would be associated with a reduced risk of death or treatment failure.Methods. We conducted a retrospective cohort study of patients initiating MDR tuberculosis treatment between 2000 and 2004 in Tomsk, Russian Federation. We used a multivariate Cox proportional hazards model to assess whether monthly exposure to an aggressive regimen was associated with the risk of death or treatment failure.Results. Six hundred fourteen individuals with confirmed MDR tuberculosis were eligible for analysis. On multivariable analysis that adjusted for extensively drug-resistant (XDR) tuberculosis—MDR tuberculosis isolates resistant to fluoroquinolones and parenteral agents—we found that monthly exposure to an aggressive regimen was significantly associated with a lower risk of death or treatment failure (hazard ratio, 0.52 [95% confidence interval, .29–.94]; P = .030).Conclusions. Receipt of an aggressive treatment regimen was a robust predictor of decreased risk of death or failure during MDR tuberculosis treatment. These findings further support the use of this regimen definition as the benchmark for the standard of care of MDR tuberculosis patients and should be used as the basis for evaluating novel therapies. [ABSTRACT FROM AUTHOR]