The hktE/pgdx double mutants of H. influenzae Rd and Hib Eagan are extremely sensitive to supranormal concentrations of exogenously supplied H
, especially under conditions of low-complex nutrient availability. Susceptibilities of the wild-type and the hktE/pgdx double mutant strains of H. influenzae Rd and Hib Eagan to H2O2 were determined by the disk diffusion assay. Disks containing H2O2 were placed on lawns of exponential-phase pregrown bacteria spread over either sBHI or MIc agar plates and incubated overnight at 37°C under anaerobic conditions. Data represent the mean zone of inhibition (in millimeters) plus the standard error of the mean (SEM) calculated from three independent experiments.