Influence Of Initial Drug Resistance On Response To Short Course Chemotherapy Of Pulmonary Tuberculosis

Abstract

This study was carried out during the period of July 1986 to December 1994 to estimate prevalence of initial drug resistance to isoniazid (H), streptomycin (S) and rifampicin (R) and to find out its effect singly or in combination on response to short course chemotherapy (SCC) as compared to drug sensitive cases of pulmonary tuberculosis. Patients aged 15 years and above who were smear positive for acid fast bacilli (AFB) (two samples) and had not taken anti- tuberculosis treatment in the past were included in the study. Sputum samples for Mycobacterium tuberculosis culture were taken and those reported positive were subjected to drug resistance tests. Drug resistant cases were matched with drug sensitive controls for age, sex, socio-economic status, extent of disease and SCC regimens (R1 = 2HRZ/ 6TH/ or EH, R2 = 2SHRZ / 6TH or EH, R3 = 2EHRZ/ 6TH or EH) and results were analyzed by applying statistical tests. The overall prevalence of initial drug resistance (IDR) was estimated to be 25.6%. It was 24.4% for H, 13.4% for S, 0.8% for R and 11.9% for SH. Significantly high level of unfavorable results were obtained in resistant cases (15.3%) than sensitive controls (5.1%). Failure and relapse rates (F+R) were less in regimens R2 and R3 with streptomycin or ethambutol (E) in the intensive phase in addition to isoniazid, rifampicin and pyrazinamide. But this gain was not statistically significant. Of single drug resistance, H resistance caused failures and relapses in 13.3% of patients while S in 6.7% of patients. Failures and relapses were high in those with resistance to two drugs (17.3%) or three drugs (100%). Rifampicin resistance in combination with other drugs caused failure in 71.4% of patients.