Drug susceptibility patterns of the Mycobacterium tuberculosis isolated from previously treated and new cases of pulmonary tuberculosis at German-Nepal tuberculosis project laboratory, Kathmandu, Nepal.

BACKGROUND

Multidrug resistant tuberculosis (MDR-TB) is a serious public health problem in Nepal. It is a major obstacle for the control of the tuberculosis. The main objectives of this study were to determine the prevalence of the multidrug resistant pulmonary tuberculosis and to evaluate the drug susceptibility patterns of Mycobacterium tuberculosis isolated from previously treated and newly diagnosed cases of pulmonary tuberculosis.

METHODS

A cross-sectional study was conducted from March 2013 to August 2013 at German-Nepal tuberculosis project (GENETUP) laboratory, Kathmandu, Nepal. For this the sputum samples from total of 153 (49 new and 104 previously treated) suspected pulmonary tuberculosis patients were used. The diagnosis of the tuberculosis was performed by using fluorescent microscopy and culture, while the drug susceptibility testing of Mycobacterium tuberculosis was performed by proportion method. Lowenstein-Jensen (L-J) medium was used for the culture of Mycobacterium tuberculosis and the colonies grown were identified on the basis of the colony morphology, pigment production and biochemical characteristics.

RESULTS

The prevalence of MDR-TB among all the cases of culture positive pulmonary tuberculosis was 15.6 %. The rate of MDR-TB among previously treated culture positive tuberculosis patients was 19.4 % and that among newly diagnosed culture positive pulmonary tuberculosis cases was 7.1 %. The highest rate of resistance of Mycobacterium tuberculosis, was toward streptomycin (24.4 %) followed by isoniazid (23 %), rifampicin (17.8 %) and ethambutol (15.6 %). Among the total of MDR-TB cases among previously treated patients, highest percentage of the cases were relapse (61.1 %) followed by chronic (16.7 %).

CONCLUSIONS

The high prevalence of DR/MDR-TB in our study reflects poor implementation of tuberculosis control program. On the basis of the drug susceptibility patterns of M. tuberculosis we found in our study, we recommend to include ethambutol instead of streptomycin in the multidrug therapy for the treatment of tuberculosis patients in Nepal. Further, due to high rate of MDR-TB among previously treated patients, we do not recommend to use first line drugs for the treatment of pulmonary tuberculosis among previously treated patients.