First-line anti-tubercular drug resistance of mycobacterial strains from re-treatment cases that were smear-positive at 4(th) month onwards under the Revised National Tuberculosis Control Program

BACKGROUND: Programmatic management of drug-resistant TB (PMDT) under the RNTCP is being implemented in West Bengal in a phased manner since 2011. During the initial years MDR-TB cases were identified based on criteria A. This study examines the first line anti-tubercular drug resistance pattern of mycobacteria cultured from sputum samples of MDR suspects who were retreatment cases smear positive from 4(th) month onwards. MATERIALS AND METHODS: In the following retrospective record based study, data on Drug Sensitivity Testing (DST) of sputum samples of MDR suspects between September 2011 and August 2012 were collected from the IRL Kolkata and analysed. Sputum samples, collected in the districts maintaining adequate aseptic containment measures, were decontaminated and centrifuged and the sediment inoculated on LJ medium. Probable M. tuberculosis colonies were identified by typical colony characteristics and Ziehl-Neelsen (ZN) staining. Sensitivity of the four 1(st) line drugs (Streptomycin, Isoniazid, Ethambutol and Rifampicin) was deduced by the economic variant of the proportion method. RESULTS: Of all the 917 MDR suspects whose sputum was examined, 64 mycobacteria culture positive strains (6.98%) were mono-resistant to any of the four first line anti-tubercular drugs. Among the mono-resistant strains 43 (4.69%) were resistant to Rifampicin while 12 (1.31%) were resistant to INH. There were a total 78 (8.51%) poly drug-resistant strains. MDR-TB strains were seen in 741 (80.81%) samples. CONCLUSION: The magnitude of drug resistance were very high among retreatment patients that were smear positive from 4(th) months onwards probably because of repeated courses of anti-tubercular drugs prior to drug sensitivity testing (DST). The decision of the PMDT to enlist all retreatment patients as MDR suspects at initiation will result in early identification and treatment of MDR-TB patients.