MOST COMMONS

The Most Common cause of resistance to the drug INH is due to the mutation of

---- katG gene

** katG gene codes for a Catalase-Peroxidase which activates the prodrug INH. Other modes of resistance involves the Mycobacterial genes - inhA gene and the KasA genes.

** One important feature about INH is that it does not show cross-resistance with other ATT drugs except---- ETHIONAMIDE (d/t it's structural similarity).