Second-line drug susceptibilities of multidrug- and rifampicin-resistant Mycobacterium tuberculosis isolates in Delhi

Background: Multidrug-resistant tuberculosis (MDR-TB) is a threat to the accomplishments of the World Health Organization's (WHO) End TB Strategy. The treatment of MDR-TB is less effective and more toxic; additional resistance to second-line drugs makes the treatment more difficult. India accounts for one-fourth of the global TB burden. In 2015 alone, 2.8 million cases of TB were diagnosed of which 79,000 cases had MDR/rifampicin-resistant TB (RR-TB). This study was conducted to analyze the baseline susceptibility pattern of MDR/RR-TB isolates against second-line drugs. Methods: A total of 374 culture-positive MDR and rifampicin-resistant M. tuberculosis isolates were tested for susceptibility against capreomycin (CAP), kanamycin, levofloxacin, moxifloxacin, clofazimine, and linezolid. Results: Of the total 374 isolates, 236 (63.10%) strains were susceptible to all drugs, whereas 138 (36.89%) were resistant at least to one of the second-line drugs. One hundred and sixteen (31.01%) strains were identified as preextensively drug-resistant (XDR) (MDR isolates with additional resistance to either fluoroquinolones or second-line injectables) and 22 (5.88%) of the isolates tested were identified as XDR. Conclusion: India is a signatory to the WHO's “The End TB Strategy” with the aim of ending the global TB epidemic; intensified efforts for early detection and treatment of drug-resistant cases from both public and private sectors are required to accelerate the rate at which TB incidence falls and accomplish the desired results.