Determination of Irradiation D-Values for Aeromonas hydrophila

Abstract

This study examined the radiation resistance of Aeromonas hydrophila, a psychrotrophic pathogen of emerging importance. Five strains of Aeromonas hydrophila (three clinical and two food isolates) were irradiated in a Cesium-137 source at doses up to 150 Krads. The bacterium was irradiated in growth broth, phosphate buffer, ground bluefish or ground beef. Surviving bacteria were counted on nutrient agar or starch ampicillin agar. Radiation resistance was expressed as D-values (dose in Krads to yield a 10-fold decrease in viable number) and ranged from 14 to 22 Krads at 2 ± 1°C for most variables studied. Decreasing the temperature during irradiation increased the radiation resistance (raised the D-values). The results of this study indicate that a pasteurizing dose of ionizing radiation of 150 Krads is sufficient to kill the levels of Aeromonas hydrophila found in retail fresh foods.