Effect of pre-incubation pH on the growth characteristics of Aeromonas hydrophila at 5°C, as assessed by two methods

Abstract

Two strains of Aeromonas hydrophila (the type strain ATCC 7966 and a food-derived strain JAH4) were pre-incubated at 5°C in Brain Heart Infusion (BHI) broth with pH adjusted to 6.0 or 7.0, and then incubated at the same temperature in BHI broth with pH adjusted to 6.0, 6.5, 7.0 and 7.5. Growth kinetics during incubation were determined by two methods: viable count (VC) and measurement of optical density (O.D.). Pre-incubation at different pH values did not significantly affect the maximum specific growth rates of the strains during incubation, but the lag phases were shorter after pre-incubation at pH 6.0 than at pH 7.0. The VC method was more sensitive than O.D. measurements for assessing lag phase.