Primary and acquired drug resistance patterns of Mycobacterium tuberculosis isolates in India: a multicenter study

Tuberculosis is the most prevalent infection worldwide. The emergence of drug-resistant Mycobacterium tuberculosis (M. tuberculosis) isolates emphasizes that it is necessary to monitor drug resistance of the organism against anti-tubercular drugs. We analyzed 327 M. tuberculosis isolates from patients who were cared for at three different health care centers, hereinafter known as study areas (SAs), in North India. Of the 327 total M. tuberculosis isolates, 255 were from a tertiary health care center (Varanasi, Uttar Pradesh [SA-1]), 48 were from a District tuberculosis center (Sawai Madhopur, Rajasthan [SA-2]), and 24 were from a different District tuberculosis center (Buxar, Bihar [SA-3]). Drug susceptibility testing against first-line antibiotics (viz. isoniazid, rifampicin, streptomycin, and ethambutol) was conducted for all the isolates using 1% proportional method. We found that the rates of acquired resistance were consistently higher than the rates of initial drug resistance. In new, untreated cases, a higher degree of MDR-TB was observed at SA-1 (13.3%) and SA-3 (25.0%), whereas it was observed in only 7.1% of the isolates at SA-2. In previously treated patients, MDR cases were found in 35.7% of the isolates from SA-1, 66.6% of the isolates from SA-2, and 43.8% of the isolates from SA-3. Resistance to a single drug was found at a much lower rate, ranging from 0.0 to 6.3% in new cases as well as previously treated cases. In conclusion, the primary resistance of M. tuberculosis is low, but acquired drug resistance is slightly higher in North India.