Multidrug-resistant tuberculosis: treatment outcome in Denmark, 1992-2007

A retrospective nationwide study including all culture-verified multidrug-resistant (MDR) tuberculosis (TB) cases was performed in Denmark. The aim was to examine the long-term treatment outcome of MDR-TB, to assess if MDR-TB transmission occurs, and to evaluate a rapid mutation analysis detecting rifampin and isoniazid resistance in this cohort. Clinical data were obtained from patient records. A restriction fragment length polymorphism genotype database of all TB cases was compared for identical strains indicating active transmission. Twenty-nine cases of MDR-TB were identified and the incidence was low at 0.5%. Acquired MDR-TB and active transmission was rare. Mutations in rifampin (rpoB) and isoniazid (katG, inhA) genes correctly determined resistance in 100% and 82% of all isolates tested, respectively. Initial treatment success was 89% for 27 MDR-TB patients with available outcome data. Initially 3 patients defaulted; no deaths were reported. Including successfully re-treated default patients and censoring patients who spent <2 y in the cohort, long-term treatment success was achieved for all 26 patients (mean follow-up 8.9 y). MDR-TB has a good prognosis in the high-income, low TB burden country of Denmark. Continued surveillance and rapid detection of resistance mutations directly in smear-positive patients may improve the standard of MDR-TB care.