Author/Authors :
Nasr Esfahani، Bahram نويسنده Department of Microbiology, Faculty of Medicine, Isfahan University of Medical Sciences, Isfahan, IR Iran , , Zarkesh Esfahani، Fatemeh Sadat نويسنده Department of Microbiology, Science and Research Branch, Islamic Azad University, Fars, IR Iran , , Rezaei Yazdi، Hadi نويسنده Department of Microbiology, Jahrom University of Medical Sciences, Jahrom, IR Iran , , Radaee، Tooba نويسنده Department of Microbiology, Isfahan University of Medical
Sciences, Isfahan, IR Iran ,
Abstract :
Ethambutol (EMB) is the first-line drug used for the treatment of
tuberculosis. Recent reports on the EMB-resistant isolates of
Mycobacterium tuberculosis in different geographical regions of the
world have revealed the EMB resistance patterns of M. tuberculosis and
mutations in the embB gene. In this study, we determined the emb locus
in sensitive and resistant Iranian M. tuberculosis isolates using two
effective methods for the detection of point mutation, i.e.,
single-strand conformational polymorphism (SSCP) and direct sequencing.
Thirty-two M. tuberculosis isolates from the Isfahan tuberculosis center
were characterized by conventional methods and specific amplification of
the regions of difference (rd) gene and internal transcribed spacer
(its) gene. Observing standard operational procedures, EMB
susceptibility tests were performed on the LJ medium using the
proportion method with 2, 5, and 10 μg/mL concentrations. PCR-SSCP and
direct sequencing were used to detect different kinds of mutation in the
embB gene with precision. In a total of 32 isolates, two isolates
(6.25%) were found to be resistant to EMB in 2, 5, and 10 μg/mL
concentrations. Single-strand conformational polymorphism showed altered
mobility with triple bands in the resistant isolates and double bands in
the sensitive isolates. In the two EMB-resistant cases, mutation was
found to occur codons 309and 299. We concluded from the results that the
frequency of EMB-resistant M. tuberculosis cases in Iran is lower than
that of many other regions. The PCR-SSCP technique can separate
resistant isolates from sensitive isolates. The sequencing results of
this study showed mutation in codons 309 and 299 of the embB gene. In
none of the resistant isolates, mutation was observed in codon 306.
Further studies are required to determine other point mutations and
analyze other genetic loci associated with EMB resistance in M.
tuberculosis isolates in Iran.
