The nationwide tuberculosis drug resistance survey in Mongolia, 1999

Mongolia, a country in the Western Pacific Region burdened with many cases of tuberculosis, with rapid expansion of DOTS over the last several years.

To determine the prevalence of resistance to major anti-tuberculosis drugs among tuberculosis patients who have never been treated previously.

Sputum specimens were collected from all smear-positive tuberculosis patients identified from 1 November 1998 to 1 May 1999.

Resistance to any of the four major drugs (streptomycin, isoniazid, rifampicin, and ethambutol) was as high as 28.9% (95%CI 24.7-33.5), primarily due to high streptomycin resistance of 24.2% (95%CI 20.3-28.6). Isoniazid resistance was also high, at 15.3% (95%CI 12.1-19.1). Resistance levels to ethambutol and rifampicin were relatively low, at 1.7% (95%CI 0.8-3.5) and 1.2% (95%CI 0.5-2.9), presumably because these drugs were only recently introduced into Mongolia. Multidrug resistance was also rare, at 1.0% (95%CI 0.1-1.8). Drug resistance rates were higher in middle-aged patients than in younger and older age groups combined (P = 0.006). Males tended to have higher resistance than females, although this was of statistically marginal significance (P = 0.08). No significant regional differences in drug resistance were found.

While multidrug resistance was rare, isoniazid resistance was very common, which necessitates closer monitoring of the treatment outcomes of individual patients as well as long-term follow-up for drug resistance on a nationwide scale.