Nationwide survey of anti-tuberculosis drug resistance in Mongolia

BACKGROUND: Drug-resistant tuberculosis (TB) has emerged as an obstacle to effective TB control. SETTING: The eight district and 21 province TB dispensaries and the two TB hospitals comprising the diagnostic centers for TB in Mongolia. METHODS: To investigate drug resistance levels among new and retreated TB cases. Specifically, we determined the prevalence of resistance to rifampin, streptomycin, isoniazid and ethambutol among TB patients with and without prior anti-tuberculosis treatment. RESULTS: A total of 850 patients (74.1% of eligible and 78.0% of patients with a specimen) had Mycobacterium tuberculosis isolated and are the subject of this analysis. Of these, 200 had a history of prior treatment and 650 did not. Any multidrug resistance was found in 7.5% (95%CI 5.9-9.5), with respectively 27.5% (95%CI 21.8-34.1) and 1.4% (95%CI 0.7-1.6) of patients with and without prior history of treatment. CONCLUSIONS: The most conspicuous finding in our survey was the relatively low prevalence of multidrug resistance among patients without a history of prior treatment, as compared to very high prevalence among previously treated patients. This suggests that retreatment is deficient and poses a threat to continued transmission, which has not yet manifested itself among new patients.