In addition, mutations in the inhA gene and its promoter region, i.e., the c-15t base change, further complicate the treatment of drug-resistant TB, conferring resistance not only to INH but also to the second-line TB drug ethionamide (ETH) (Banerjee et al., 1994), with reported frequencies of 35% and 55% in INH- and ETH-resistant clinical isolates, respectively (Vilcheze and Jacobs, 2014). Here, INHA is linked to tuberculosis.