Prevalence and drug resistance profile of Mycobacterium tuberculosis isolated from pulmonary tuberculosis patients attending two public hospitals in East Gojjam zone, northwest Ethiopia.

Background: The spread of multidrug-resistant tuberculosis (MDR-TB) strains has become a challenge to the global TB control and prevention program. In Ethiopia, particularly in rural areas, information on drug-resistant TB is very limited. In this study, we determined the drug resistance patterns of Mycobacterium tuberculosis (M. tuberculosis) isolates from pulmonary TB patients attending two public hospitals in the East Gojjam zone of northwest Ethiopia.

Methods: A cross-sectional study was conducted between May 2011 and January 2012 using Region of difference-9 (RD9) typing for the identification of species mycobacterium. Drug susceptibility testing (DST) of M. tuberculosis isolates to the first-line drugs: isoniazid, rifampicin, ethambutol and streptomycin was performed by the indirect proportion method on Middle brook 7H10 Agar media.

Results: Out of 385 pulmonary TB suspects studied, 124 (32.2%) were culture positive among which 120 were M. tuberculosis strains. Susceptibility testing was performed for 89 isolates. Resistance to at least one drug was 15.58% ([12/77], 95% CI: 7.48-23.68) among newly diagnosed and 50.0% ([6/12], 95% CI: 21.71-78.29) among previously treated cases. Resistance among newly diagnosed patients was most common for streptomycin 5.19% (4/77) and ethambutol 5.19% (4/77) followed by rifampicin 3.89% (3/77). Among retreatment cases, isoniazid resistance was most frequent in which 33.33% (4/12) of the isolates were resistant. MDR prevalence was 1.29% (1/77) for newly diagnosed and 16.67% (2/12) for retreatment cases. In a multivariate logistic regression analysis, age group of 25-34 years (adjusted OR = 4.24; 95% CI: 1.02-17.5; P = 0.046) and previous history of treatment (adjusted OR = 5.42; 95% CI: 1.56-27.49; P = 0.01) were independently associated with anti-TB drug resistance.

Conclusions: In general, the magnitude of anti-TB drug resistance including MDR-TB was comparable to previous studies in other areas of Ethiopia. However, rifampicin resistance was high, which could suggest the potential for a rise in the incidence of MDR. Therefore, re-enforcing TB control programs should be considered by the concerned public health authorities.