Abstract

Isoniazid resistant Mycobacterium tuberculosis strains are a serious threat for successful tuberculosis control programs. Therefore, present study was aimed to figure out the pattern and level of resistance of M. tuberculosis against isoniazid. A total of 172 specimens of sputum, pus and bronchial washings; 70.9% males and 29.1% females with 84.30% pulmonary and 15.69% extrapulmonary tuberculosis were collected from six different sources. The inoculums were prepared using 0.5 Mac Farland turbidity standards. Five concentrations of isoniazid were used in Lowenstein Jensen (LJ) medium that is 3, 6, 9, 12 and + 12 μg/ml for sensitivity testing. Data showed 25 (14.5%) resistant and 147 (85.5%) sensitive M. tuberculosis strains. The growth was not inhibited at first (3 μg/ml) and second (6 μg/ml) drug levels, while 36% isolates inhibited at third level (9 μg/ml), 28% at forth level (12 μg/ml) and 24% at fifth level (10 μg/ml) and 12% at higher than fifth Level (> 12 ug/ml). These incorporated drug concentrations are higher than therapeutic index and not recommended in actual clinical practice. It is thus obvious to explore some other effective chemotherapeutic agents, modify combinations or figure out more effective procedures to stop morbidity and mortality due to isoniazide resistance ofM. tuberculosis.

Key words: Isoniazid, mycobacterium tuberculosis, resistance, Lowenstein Jensen medium.