Tomatidine is bacteriostatic against SCVs but not against normal strains. (A) Samples (10 μl) from cultures treated with various concentrations of tomatidine following the antibiotic susceptibility testing procedure (see Materials and Methods) were spotted on agar plates and photographed. Time-kill experiments showing the effect of tomatidine (TO), tomatine (TN), erythromycin (ERY), or ciprofloxacin (CIP) on the growth of the normal strain CF07-L (B) and of the SCV CF07-S (C). Concentrations of 16 μg/ml of TO (n = 3), 0.5 μg/ml of ERY (n = 3), and 1.0 μg/ml of CIP (n = 3) were used against CF07-L, whereas concentrations of 0.25 μg/ml of TO (n = 4), 16 μg/ml of TN (n = 3), 0.25 μg/ml of ERY (n = 3), and 0.5 μg/ml of CIP (n = 2) were used against CF07-S. The no-drug control experiments are from four independent experiments.