Kinetics of recA and recX induction in drug-susceptible and MDR clinical strains of Mycobacterium tuberculosis

Objectives: To investigate and compare the expression ofrecA andrecX, components of the SOS pathway, following rifampicin treatment in drug-susceptible and MDR clinical strains of Mycobacterium tuberculosis. Methods: Strains (M. tuberculosis and Mycobacterium smegmatis) were subjected to rifampicin- and mitomycininduced stress for 36 h followed by RNA extraction.recA andrecX in the RNA extract were estimated using qRT–PCR. Results: The MDR clinical strain induced faster (24 h) and higher (7-fold) levels ofrecA as compared with the drugsusceptible strain (36 h) in response to rifampicin. recX levels were found to rise with an increase in levels of recA; however, the levels were relatively higher than recA. Conclusions: Drug-susceptible and MDR strains have different kinetics of induction of DNA repair.