The combined effects of pH and temperature on growth of three serotypes of salmonellae are reported. Salmonela heidelberg grew on the surface of agar over the pH range of 5.0 to 9.0. Minimum growth temperatures of 5.3, 5.2, and 5.3 C were obtained at pH values of 6.0, 7.0, and 8.0, respectively. In broth, S. heidelberg increased in number over the pH range of 6.0 to 8.0, with the lowest growth temperature of 6.0 C obtained at pH 7.0. Salmonella typhimurium increased in number in broth at pH values of 6.0 to 9.0. A time-temperature effect was shown by this organism after 16 days. Salmonella derby grew over the pH range of 6.0 to 8.0 in broth, with the lowest growth temperature of 9.0 C obtained at pH 6.0 and pH 7.0. The results indicate that food-poisoning Salmonella serotypes grow only over a narrow pH range at low temperatures.
1Contribution No. 354, College of Fisheries, University of Washington, Seattle, Washington 98195. This investigation was supported by the U. S. Public Health Service Research Grant 5 RO1 UI 00248-02 from the Consumer Protection and Environmental Health Service, Food and Drug Administration.