Effect of additional drug resistance of M tuberculosis in patients with Hr-TB on the efficacy of chemotherapy

<b>Introduction:</b> Patients with isoniazid-resistance and rifampicin-sensitivity pulmonary tuberculosis (Hr-TB) can have resistance to other anti-TB drugs. Incorrect treatment may increase the resistance of mycobacteria TB (MBT) and develop multidrug and extensively drug-resistant TB. In the Russian Federation (RF), levofloxacin (Lfx) and capreomycin (Cm) are key drugs for treatment of Hr-TB, with addition of three 1st-line anti-TB drugs. <b>Objective:</b> To determine the effect of additional drug resistance (DR) of MBT in patients with Hr-TB on the efficacy of chemotherapy. <b>Methods:</b> We studied MTB drug resistance (DR) in 1379 Hr-TB patients started treatment in 2015 from 18 regions of the Russian Federation. All patients were distributed into 4 groups: group 1- DR to Lfx and Cm - 23/1379, group 2 – DR to Lfx and drug sensitivity (DS) to Cm - 56/1379, group 3 - DS to Lfx and DR to Cm - 41/1379, group 4 - DS to Lfx and Cm -1259/1379. Unfavorable outcome was registed in patients with culture positive at the 5th month of chemotherapy. <b>Results:</b> Significance of additional DR of MBT in Hr-TB patients was defined. Statistically significant differences were revealed between 1 and 4 groups. In the case of MBT sensitivity to fluoroquinolone and polypeptide, an unfavorable outcome was determined in 12.8% (162/1259), while in the case of resistance to fluoroquinolones and polypeptide in 34.7% (8/23) (OR=3.44;p&lt;0,05) [95% CI 1.4 – 8.43]. <b>Conclusion:</b> DR simultaneously to both TB-drugs (Lfx, Cm) is a predictor of unfavorable outcome in Hr-TB cases, compared to the preserved sensitivity to both TB-drugs.