• Evidence of an association between the embB gene and ethambutol resistance in Mycobacterium tuberculosis patients by multiplex allele-specific polymerase chain reaction (MAS-PCR) in Ardabil, Iran
  • Forough babazadeh,1 Zahra hosseinali,2,* Jafar mohammadshahi,3
    1. Department of Microbiology, School of Medicine, Ardabil University of Medical Science, Ardabil, Iran
    2. Department of Microbiology, School of Medicine, Ardabil University of Medical Science, Ardabil, Iran
    3. Department of Infectious Diseases, School of Medicine, Ardabil University of Medical Sciences, Ardabil, Iran


  • Introduction: Tuberculosis (TB) is an extremely infectious sickness due to Mycobacterium tuberculosis (M. tuberculosis) which is life-threatening. Recently, it was found that one of the most important factors for the rapid spread of TB is the development of resistance to valuable anti-TB drugs. Various drugs such as isoniazid (INH), rifampicin (RIF), streptomycin (SM), pyrazinamide (PZA), and ethambutol (EMB) are used to treat TB. improper use of these drugs leads to resistance. Ethambutol (EMB) is one of the first-line drug regimens for pulmonary tuberculosis therapy, and resistance to this drug is increasingly reported in many parts of the world. It should not be used alone but can be prescribed in combination with at least one other antituberculosis agent such as isoniazid. EMB is effective against strains of M. tuberculosis, but not so much against viruses, fungi, or other bacteria. Mutation in embB is the main mechanism of resistance. The purpose of this study is to investigate the relationship between the mutation in embB gene and ethambutol resistance in M. tuberculosis using the MAS-PCR method.
  • Methods: As part of a cross-sectional study, 63 infected sputum and bronchoalveolar lavage samples (BAL) were collected from patients referred to the Ardabil Provincial Health Center for TB between July 2016 and June 2020. The boiling method was used for whole DNA extraction from clinical samples as described previously. MAS-PCR method was employed for detection of mutations embB which confer resistance to ethambutol.
  • Results: In the present study, 34 out of 63 samples (53.96%.) harbored a mutation in embB gene which mediated resistance to ethambutol.
  • Conclusion: In this study, high mutation rates leading to resistance to EMB were observed. EMB-resistant MTB were common, especially those with an embB mutation. Tracking embB mutation among EMB-resistant isolates would be diagnostically and epidemiologically valuable. According to the results, " MAS-PCR can not only be used as a simple and rapid method for detecting EMB resistance in M. tuberculosis strains but also provides accurate and reliable results in less time than other methods. Regular monitoring of drug resistance and expansion of drug resistance testing facilities is imperative to prevent the transmission of drug-resistant TB in the community and also, provide primarily valuable data in administrating suitable drugs for combating tuberculosis.
  • Keywords: Ethambutol (EMB), Mycobacterium tuberculosis, MAS-PCR, Drug resistance, Mutations