Resistance genotypes of multidrug-resistant Mycobacterium tuberculosis isolates in Serbia

<b>Background:</b> Multidrug-resistant (MDR) tuberculosis (TB) presents a global threat. Better understanding of drug resistance-conferring mutations and their effect on bacterial transmission and clinical course of disease, may contribute to improved TB control measures. The aim of our study was to determine frequency of these mutations in MDR <i>M. tuberculosis</i> strains isolated in Serbia, to compare resistance genotypes of local isolates with those of different geographic origin, and to investigate possible correlation between resistance genotypes and clinical course of MDR TB. <b>Methods:</b> In total, 70 M. tuberculosis strains isolated from the specimens of all MDR TB patients registered in Serbia from 2009–2012, were analyzed. For all patients demographic and clinical information was collected. Presence of mutations in rpoB, katG and inhA genes was analyzed. <b>Results:</b> The most frequent mutations observed were S531L in rpoB gene, S315T1 in katG gene and ΔWT2 in inhA gene. The frequencies of four major genotypes of resistance were 31%, 11%, 7% and 5,6%, respectively. The most common genotype of resistance was rpoB:ΔWT8, S531L; katG:ΔWT, S315T1; inhA:WT. Among MDR TB patients whose strains displayed this genotype, significantly more new cases were observed. <b>Conclusion:</b> The most frequent mutations and genotypes of resistance of the analyzed strains were similar to predominant genotypes of resistance of MDR TB bacilli isolated in other European countries. The significant association between the most common genotype of resistance in this study population and the absence of prior history of TB suggests active transmission of strains with this genotype, i e importance of MDR TB transmission in Serbia.