detection of <i>embb</i> gene mutations in emb-resistant <i>mycobacterium tuberculosis</i> isolates from isfahan province by pcr-sscp and direct sequencing

Background]ethambutol (emb) is the firstline drug used for the treatment of tuberculosis. recent reports on the embresistant isolates of <i>mycobacterium tuberculosis</i> in different geographical regions of the world have revealed the emb resistance patterns of <i>m. tuberculosis</i> and mutations in the <i>embb</i> gene.[objectives]in this study, we determined the <i>emb</i> locus in sensitive and resistant iranian <i>m. tuberculosis</i> isolates using two effective methods for the detection of point mutation, i.e., singlestrand conformational polymorphism (sscp) and direct sequencing.[methods]thirtytwo <i>m. tuberculosis</i> isolates from the isfahan tuberculosis center were characterized by conventional methods and specific amplification of the regions of difference (<i>rd</i>) gene and internal transcribed spacer (<i>its</i>) 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. pcrsscp and direct sequencing were used to detect different kinds of mutation in the <i>embb</i> gene with precision.[results]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. singlestrand conformational polymorphism showed altered mobility with triple bands in the resistant isolates and double bands in the sensitive isolates. in the two embresistant cases, mutation was found to occur codons 309and 299.[conclusions]we concluded from the results that the frequency of embresistant <i>m. tuberculosis</i> cases in iran is lower than that of many other regions. the pcrsscp technique can separate resistant isolates from sensitive isolates. the sequencing results of this study showed mutation in codons 309 and 299 of the <i>embb</i> 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 <i>m. tuberculosis</i> isolates in iran.