Chlamydia trachomatis is the most common sexually transmitted bacterial infection worldwide. Often, infections occur asymptomatically, leading to serious health complications in the absence of treatment. The use of azithromycin and doxycycline is recommended for the treatment of sexually transmitted chlamydial infections. Both antibiotics belong to the group of bacteriostatic antibiotics that bind to 23S rRNA and 16S rRNA, blocking protein synthesis. Treatment failure rates are high (8-23 %), for which the most common cause is re-infection after discontinuation of treatment or the development of heterotypic resistance. The most commonly used test for antibiotic susceptibility and MIC determination is cultivation in cell culture in the presence of antibiotics in various concentrations. Resistance to macrolides may be due to mutations in the 23S rRNA gene that cause reduction in interaction of antibiotics with target site of action. The aim of this master's thesis is to establish an effective method for determination of mutations in the domain V of 23S rRNA that mediate resistance to macrolides, so we included 58 DNA samples of clinical isolates with confirmed C. trachomatis infection after antibiotic treatment. 36 DNA samples were successfully amplified with allele-specific oligonucleotides and sequencing was performed. Based on bioinformatics analysis at positions A2057, A2058, A2059 and T2611 (E. coli numbering), we did not find mutations that are important for the development of resistance to macrolides. Based on expectations, we have successfully established a molecular method to obtain nucleotide sequences, whereby the presence of important mutations that mediate resistance to macrolides can be determined based on alignments with reference sequences.
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