The Nationwide Tuberculosis Drug Resistance Survey in Mongolia, 1999

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

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

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

RESULTS: 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.

CONCLUSION: 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.