Multidrug resistant tuberculosis (MDR-TB) belongs to the most serious forms of TB. The number of MDR-TB patients represents an indictor of the effectiveness of TB regimentation. The aim of the study was to determine the number of registered MDR-TB patients in CR in 1998 and to identify causes of the resistance. Analysis of clinical documentation of 27 patients with MDR-TB positive sputum was done in 1998. According to the documentation, this form of tuberculosis was not confirmed in 5 persons. Out of 22 patients with confirmed MDR-TB, 21 were males and one female. In 3 of them we could not reveal whether they had been cured with antituberculotics before MDR-TB developed. Such resistance was then classified as an initial form. In 19 patients we found that resistance developed during treatment. Those cases were classified as secondary forms. In 16 patients the secondary resistance was related to the interruption of treatment, which was done wantonly by the patients in 14 cases. The consistent treatment of the sensitive TB is therefore the best prevention for MDR-TB development. Incidence of MDR-TB cases has not been influenced by immigration from countries with high rate of occurrence of MDR-TB.

        Key words: tuberculosis, MDR-TB, resistance, interruption of treatment.