160 Reviews in Infection RIF RIF 1(3):160-165 (2010) ISSN:1837-6746 Detection and frequency of mutation in the rpoB gene of Mycobacterium tuberculosis isolates from patients with active Pulmonary Tuberculosis in different regions of Tehran City *Saeed Zaker Bostanabad 1,2,6 , Mehrdad Hashemi 3,5 , Mohammad Karim Rahimi 4 , Fahimeh Ostadzadeh 3 , Mohammad Bossak 4 , Sajjad Nouri 3 , Shahin Pourazar 2 , Mostafa Ghalami 2,8 , Mehdi shekarabei 2,7 , Hassan Hoseinaei 2 , Esmaeil Jabbarzadeh 10 , Seyed Ali Nojoumi 10 , Vahid Molla Kazemi 9 , Zahra Tayebei 4 , Mozhgan Masoumi 4 , Veronica Slizen 6 , Evgeni Romanovich Sagalchyk 6 and Leonid Petrovich Titov 6 1 Islamic Azad University, Parand branch, Biology and Microbiology Department, Iran 2 Masoud Laboratory, Mycobacteriology Department, Iran 3 Islamic Azad University, Science Branch, Genetic Department, Iran 4 Islamic Azad University, Tehran Medical Branch, Microbiology Department, Iran 5 Islamic Azad University, Tehran Medical Branch, Molecular Genetic, Iran 6 Belarusian Research Institute of Microbiology and Epidemiology, Clinical Microbiology, Iran 7 Iran Medical University, Immunology Department, Iran 8 National Reference laboratory, Ministry of Health in Iran 9 Pasteur Institute of Iran, Cell Bank Department, Iran 10 Pasteur Institute of Iran *Corresponding author: Saeedzaker20@yahoo.com Abstract The aim of this study was to investigate the frequency, location and type of rpoB mutations in Mycobacterium tuberculosis isolated from patients in Tehran City. 145 sputums were collected from suspected tuberculosis patients, 20 Rif-r isolates were identified as Mycobacterium tuberculosis. PCR Amplification and DNA sequencing methods were performed. 411 bp fragments of rpoB gene were sequenced and mutations in 81 bp regions were analyzed. 20 mutations were identified in 14 RIF-r MBT (70%). Missense mutations produced 20 types of amino acid substitutions. In 6 RIF-r MBT isolates (30%) no mutations were found in the core region of the rpoB gene. Most frequent mutations detected from Tehranian strains were in codons 531 and 515. Two alleles in codon 531 and one allele in all codons 526, 515, 510, 566, 490 and 476 were found. In the 6 isolates were identified 2 mutation in different codons and 8 strains harboured single mutations in codons. In this study, has been investigated the significance of mutations in the rpoB gene, its correlation with genotype and phenotype agents and high level of resistance to rifampicin in 14 isolates of M. tuberculosis collected from patients with active pulmonary tuberculosis from different geographic regions of Tehran. Introduction Mycobacterium tuberculosis is the most successful human pathogen worldwide, responsible for 3 million deaths each year and extensive morbidity and mortality (World Health Organization 1998). By the end of 2004, 199 (94%) of 211 countries notified 4.2 million new and relapsed cases, of which 1.9 million (44%) were new sputum smear-positive. A correla- tion between high mutation rate, antibiotic resistance and virulence in bacteria has been reported in several studies (Bostanabad et al., 2007). Correlations between mutation rates, geographical distribution of mutations, antibiotic resistance and virulence in bacteria have been reported in several studies (Ma- krousov et al., 2002; Bostanabad et al., 2007). Tehran is one of the oblast and capital of Iran (metropolis) that many people travel towards Tehran city from other countries and other cities of Iran (endemic region; Zabol [Afghanistan border]- Gorgan [Turkmenistan border] - Tabriz [Azerbaijan border] and Iraq border) with active pulmonary tuberculosis. Border of Iran is endemic region in Asia with 10-13 % multiple drug resistant (MDR) among 141 tuberculosis cases per 100,000 populations (Zakerbostanabad et al., 2008). Rifampicin is typically and first line drug used to treat Mycobacterium infections including tuberculosis with multi drug therapy used as the standard treatment. Rifampicin has proven to be an effective anti tuberculosis agent and its use has greatly shortened the duration of chemotherapy for the treatment of TB. Rifampicin resistance heralds higher rates of treatment failure and death for the patient and a poor outcome if the isolate is also resistant to isoniazid. The increasing incidence of multi drug-resistant tuberculosis (MDR-TB), defined as resistance to at least rifampicin and isoniazid, is a notable global health problem (Bakonyte et al., 2005; Dvorska et al., 2001; Garsia et al., 2002; Leung et al., 2003 Makorousev et al., 2002; Bostanabad et al.,; 2007). The detection of resistant M. tuberculosis strains is generally perfo-