Mutation EthA W21R confers co-resistance to prothionamide and ethionamide in both Mycobacterium bovis BCG and Mycobacterium tuberculosis H37Rv

Ethionamide (ETA) and prothionamide (PRO) are interchangeably used in tuberculosis (TB) chemotherapy regimens. Subtle discrepancies between biochemical and genetic information on the modes of sensitivity and resistance of isoniazid (INH) and ETA warrants further studies. We report a new mutation – EthAW21R – in Mycobacterium bovis Bacillus Calmette-Guérin that corresponds with co-resistance to both PRO and ETA, which to the best of our knowledge has not been reported before. Our findings suggest that mutation EthAW21R could be used as a marker site for testing PRO and ETA cross-resistance.