Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 1 1 2009 03 15 13 21 EN Saeed Zakerbostanabad Department of Clinical Microbiology, Belarusian Research Institute for Epidemiology and Microbiology, Minsk, Belarus AND Deptartment of Mycobacteriology and Pulmonary Research; Pasteur Institute of Iran, Tehran, Iran. V Molla Kazemi Department of Microbiology, Faculty of Medicine, Islamic Azad University of Tehran, Tehran, Iran. MK Rahimi Cell Bank of Iran, Pasteur Institute of Iran,Tehran, Iran. Shahidi SH Shahidi Deptartment of Mycobacteriology and Pulmonary Research; Pasteur Institute of Iran, Tehran, Iran. SH Pourazar Department of Clinical Microbiology, Belarusian Research Institute for Epidemiology and Microbiology, Minsk, Belarus. M Massomi Deptartment of Mycobacteriology and Pulmonary Research; Pasteur Institute of Iran, Tehran, Iran. A Nour Nemattolahi Deptartment of Mycobacteriology and Pulmonary Research; Pasteur Institute of Iran, Tehran, Iran. F Abdolrahimi Deptartment of Mycobacteriology and Pulmonary Research; Pasteur Institute of Iran, Tehran, Iran. LK Surkova Tuberculosis and Pulmonary Research Institute, Minsk, Belarus. M Ghazanfari Deptartment of Mycobacteriology and Pulmonary Research; Pasteur Institute of Iran, Tehran, Iran. LP Titov Department of Clinical Microbiology, Belarusian Research Institute for Epidemiology and Microbiology, Minsk, Belarus. 2015 10 01 Background and Objectives: The aim of this study was to investigate the significance of multiple-mutations in the katG gene, predominant nucleotide changes and its correlation with high level of resistance to isoniazid in Mycobacterium tuberculosis isolates that were randomly collected from sputa of 42 patients with primary and secondary active pulmonary tuberculosis from different geographic regions of Belarus. Materials and Methods: Drug susceptibility testing was determined using the CDC standard conventional proportional method. DNA extraction, katG amplification, and DNA sequencing analysis were performed. Results: Thirty four (80%) isolates were found to have multiple-mutations (composed of 2-5 mutations) in the katG. Increased number of predominant mutations and nucleotide changes were demonstrated in codons 315 (AGC→ACC) , 316 (GGC→AGC) , 309 (GGT→GTT) with a higher frequency among patients bearing secondary tuberculosis infection with elevated levels of resistance to isoniazid (MIC μg/ml ≥ 5-10) . Furthermore it was demonstrated that the combination of mutations with their predominant nucleotide changes were also observed in codons 315, 316, and 309 indicating higher frequencies of mutations among patients with secondary infection respectively. Conclusion: In this study 62% (n=21) of multi-mutated isolates found to have combination of mutations with predominant nucleotide changes in codons 315 (AGC→ACC) , 316 (GGC→GTT) , 309 (GGT→GGT) , and also demonstrated to be more frequent in isolates of patients with secondary infections, bearing higher level of resistance to isoniazid (≥ 5 -10μg/ml). https://ijm.tums.ac.ir/index.php/ijm/article/view/3 https://ijm.tums.ac.ir/index.php/ijm/article/download/3/3