Tuberculosis caused by resistant M. tuberculosis strains poses a serious threat as it requires prolonged and costly treatment and has high mortality rate. In order to investigate resistance to antituberculous drugs in Croatia, we analysed all resistant M. tuberculosis strains isolated from patients' samples in period 2010-2014 (1 strain per patient). Out of 2384 M. tuberculosis strains, we identified 88 (3.69 %) resistant strains. The analysis included resistance patterns, resistance conferring mutations and, according to MIRU-VNTR analysis, clustering and global lineages distribution. Relatively high number of strains was monoresistant, especially to isoniazid, while there were only six multiresistant strains. Among 59 strains with any pattern that includes resistance to isoniazid, a total of 22 (37.29 %) had resistance conferring mutation in katG gene (S315T), 23 (38.98 %) in inhA promoter region (C-15T) and 14 (23.73 %) had none of these mutations. The observed clustering rate of resistant strains was 28.41 %, and the most common global lineage was Euro-American (75 %).
Keywords: Clustering rate; Global lineages; Isoniazid resistance; Resistance conferring mutations; Resistant tuberculosis.