title: Application of Deletion- Targeted Multiplex PCR technique for detection of Mycobacterium tuberculosis Beijing strains in samples from tuberculosis patients.
abstract: OBJECTIVE
  Molecular epidemiological studies have shown that certain genotypes of Mycobacterium tuberculosis (MTB) are over-represented in limited geographical regions, suggesting of evolution of certain genotypes with increasing virulence and pathogenicity. Beijing strain of MTB was initially described by its potential to cause outbreaks worldwide and its association with drug resistance. Due to tuberculosis (TB)-related mortality which is associated with Beijing genotype, this study was designed with the aim to detect the MTB Beijing genotype in the region of study.
  
  
  METHODS
  A total of 170 clinical isolates of MTB were collected from the TB reference laboratory of Khuzestan province, Iran, over one year period from February 2010 to February 2011. Phenotypic tests were used for preliminary detection of MTB. Culture positive MTB isolates were confirmed by multiplex PCR based on IS6110 gene with subsequent screening for resistance to isoniazid (INH), and rifampin (RIF) by PCR using relevant primers. Three set of primers were used to differentiate Beijing from non-Beijing strains by using Deletion- Targeted Multiplex (DTM) PCR.
  
  
  RESULTS
  From 160 PCR-confirmed MTB isolates, 18 (11.25%) showed mutation in katG gene related to INH resistance and 20 (12.5%), associated with mutation in rpoB gene related to RIF resistance, and 8 (5%) were detected as Beijing strain using multiplex PCR. The majority of detected Beijing strains (6/8[75%]) comprised mutation in katG gene with the prevalent mutation specifically in codon 315. In 4 Beijing strains (2.5%), mutation in rpoB gene were also detected.
  
  
  CONCLUSIONS
  Using DTM- PCR, the rate of Beijing strains in the region of study was determined as 5%. Although for detection of MTB antimicrobial resistance, it is advised to use a combination of conventional antimicrobial susceptibility testing and molecular techniques, however for time saving, it seems that DTM-PCR, is a simple technique for use in areas of the world where Beijing strains are highly prevalent.
authors.affiliation: Health Research Institute, Infectious and Tropical Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran ; Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors.forename: Azar Dokht
authors.initials: AD
authors.lastname: Khosravi
authors.affiliation: Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors.forename: Hamed
authors.initials: H
authors.lastname: Goodarzi
authors.affiliation: Health Research Institute, Infectious and Tropical Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors.forename: Seyed Mohammad
authors.initials: SM
authors.lastname: Alavi
authors.affiliation: Department of Statistics, Mathematical Science and Computer Faculty, Shahid Chamran University, Ahvaz, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Akhond
keywords: Beijing strain; DTM PCR; M. tuberculosis; mutation
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