National Research Institute of Tuberculosis and Lung Disease (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran TANAFFOS (Respiration) 1735-0344 5 1(winter) 2006 01 01 katG Mutation of Isoniazid-Resistant Isolated from Tuberculosis Patients 31 36 241423 EN Saeed Zaker Bostanabad Belarusian State Medical University Pasteur Institute of Iran Ali Akabar Velayati National Research Institute of Tuberculosis and Lung Disease, Shaheed Beheshti University of Medical Sciences and Health Services Mohammad Reza Masjedi National Research Institute of Tuberculosis and Lung Disease, Shaheed Beheshti University of Medical Sciences and Health Services Leonid P Titov Belarusian State Medical University, Belarusian Research Institute for Epidemiology and Microbiology, Minsk, Belarus, Mohammad Taghikhani Institute of Pulmonology, Minsk, Belarus Biochemistry Department, School of Medical Sciences, Tarbiat Modarres University Hossein Ali Khazaei Zabol University of Medical Sciences Asghar Aghamohammadi Tehran University of Medical Sciences and Health Services. Ahmad Reza Bahrmand Pasteur Institute of Iran, Journal Article 2021 01 05 Background: The emergence of drug-resistant strains of Mycobacterium tuberculosis (MTB) is an increasing problem in developed and developing countries. The aims of the present study were to identify various types of mutations in katG region from 28 MDR strains isolated from sputum of tuberculosis patients. Materials and Methods: Twenty-eight rifampin-resistant strains isolated from sputum of patients with active pulmonary tuberculosis were obtained from various geographic regions of Iran. Drug susceptibility was determined by using the BACTEC system. DNA extraction, standard PCR identification, katG gene amplification, DNA sequencing and analysis were done. Results: There was no mutation in 2 strains. In 20 strains, mutation was shown to be in codon 315. Three types of mutations were detected consisting of AGC→ACC (Ser→Thr) (80%), AGC→AGG (Ser→Arg) (5%) and AGC→AAC(Ser→Asn) (15%).Furthermore, one type of mutation was seen in codons 311, 299, and 323. Twelve strains showed one mutation in codon 315 (46%), 7 strains 2 mutations (27%), 5 isolate 3 mutations (19%) and in 2 strains 4 mutations (8%) were observed in different codons. Nine silent mutations was demonstrated in codon 311(GAC→TAC ). Conclusion: This research demonstrated that mutations were mostly seen in codons 315 and 299 indicating resistance to isoniazide. (Tanaffos 2006; 5(1):31- 36) https://www.tanaffosjournal.ir/article_241423_027ef20f330f76a005613ea3ccf71dfd.pdf