Primary drug resistance against Mycobacterium tuberculosis in Karachi

To evaluate the primary drug resistance of new culture positive cases of pulmonary tuberculosis in Karachi.

All new suspected pulmonary tuberculosis patients were recruited initially. They were instructed to produce three-sputum samples for smear examination and on one of the specimen's culture was applied. Bronchoscopy and bronchial wash was done in patients who were not expectorating. Bronchial wash was then applied for both smear and culture for Mycobacterium tuberculosis.

Out of 79 cases recruited initially, 52 were able to produce sputum while bronchoscopy was performed in the remaining. AFB direct smear was positive in 32/52 sputum and 12/27 bronchial wash samples. Later, 02 sputums and 04 bronchial washes became culture positive which were initially smear negative. All cultures were of Mycobacterium tuberculosis species. These fifty culture positive cases were then included in the final analysis. Pyrazinamide was the most sensitive drug i.e. 49 isolates (98%). The resistance pattern is as follows: Streptomycin 13(26%), Isoniazid 08 (16%), Ethambutol 08 (16%), Rifampicin 04 (08%) and Pyrazinamide one (02%). Multi-Drug Resistant tuberculosis was observed in 02 (04%) patients.

In this small study, the high prevalence of primary resistance against streptomycin, INH and Ethambutol raises an urgent need of a proper nationwide survey to evaluate the true picture of primary resistance.