Identification of gene mutations in rpoB gene of rifampicin resistant isolates of Mycobacterium tuberculosis by automated DNA sequencing

Susceptibility testing was done on L.J. medium by using absolute concentration method as adopted by Canetti et al., (1969). Out of 34 isolates including in this study 10 (29.41%) and 13 (38.23%) were found to be totally resistant at the drug concentration of 64 mg/ml and 40 mg/ml respectively. Amplification of rpoB gene was attempted in 9 resistant isolates and reference M. tuberculosis H37Rv strain. This locus could be amplified in 8 isolates. Out of 9 resistant isolates 2 isolates and one reference of strain H37Rv were analyzed for gene sequencing. In two isolates missense mutation was detected at codon 531, TCG→ TTG (Ser→Leu). Identification of new mutation require the need for more studies to explore any new mutation.