Prevalence of initial drug resistance to M. tuberculosis in new sputum positive RNTCP patients.

There is an increased prevalence of drug resistant M. tuberculosis strains and of these, multi drug resistant organisms are of particular concern. With the implementation of Revised National Tuberculosis Control Programme (RNTCP) allover the state of Delhi, Initial drug resistance (IDR) to Isoniazid and Rifampicin assumes great importance and needs to be monitored on a regular basis. We undertook to study the IDR against the first line essential drugs i.e. Isoniazid (H), Rifampicin (R), Ethambutol (E) and Streptomycin (S) from April 1999 to March 2000 in newly diagnosed sputum positive cases of pulmonary tuberculosis attending TB clinics under RNTCP in Delhi. A total of 157 consecutive new smear positive patients attending TB clinics under RNTCP were taken into the study. All sputum samples were subjected to culture and drug sensitivity tests on LJ medium after decontamination of samples by Petroff's method. Resistance was expressed as the percentage of colonies that grow on critical concentration of the drugs. To determine the proportion of resistance, the number of colonies on the control and the number of colonies on the drug medium were determined. A total of 94.77% samples were sensitive to the four first line essential drugs and IDR to any drug was 5.22%. The resistance to Rifampicin alone was nil but the resistance to Isoniazid alone was 2.24%. Combined resistance to both Rifampicin and Isoniazid was 2.98 %. The incidence of resistance to first line drugs in tuberculosis is not very high among new sputum positive patients attending TB clinics under RNTCP.