MIC determination and susceptibility testing for the strains exposed to isoniazid in the presence and absence of efflux inhibitors.

Legend: INH: isoniazid; INH (a): exposure process A; INH (b): exposure process B. S: susceptible; R: resistant. Values in bold correspond to full reversion of the INH resistance phenotype. EIs were used at ½ of their MIC. MICs for the EIs (passage 1): thioridazine (TZ): H37Rv and 359/03: 15 µg/ml, 401/06 and 267/05: 30 µg/ml; chlorpromazine (CPZ): 30 µg/ml for all strains; verapamil (VP): 256 µg/ml for all strains. MICs for the EIs (passage 26): TZ: H37Rv and 359/03: 15 µg/ml, 401/06(a)26: 15 µg/ml; 401/06(b)26: 30 µg/ml; 267/05: 30 µg/ml; CPZ: MIC of 30 µg/ml for all strains except H37Rv INH(a)26: 15 µg/ml; VP: 256 µg/ml for all strains except H37Rv INH(a)26 and 401/06: 128 µg/ml.