MINIMUM AND MAXIMUM TEMPERATURES FOR GROWTH AND VEROTOXIN PRODUCTION BY HEMORRHAGIC STRAINS OF ESCHERICHIA-COLI

The influence of temperature on growth and verotoxin production by Esc herichia coli strains was studied in brain heart infusion (BHI) broth both in shake cultures at various temperatures and in a temperature-gr adient incubator. All strains of E. coli surveyed grew from at least 1 0 to 45 degrees C, with some strains growing at 8 degrees C. Verotoxin production (determined using the Vero cell-assay system) was a functi on of both temperature and time, with the highest titers produced at t emperatures supporting the fastest growth (based on days to visible tu rbidity) and highest viable cell counts. However, for strains producin g verotoxin, toxin production was detected at any temperature supporti ng growth. Three strains (of 16 tested) increased 1000-fold in viable count in 4 to 6 days at 10 degrees C. The data presented here indicate that most E. coli strains surveyed can easily grow at ca. 10 degrees C and thus suggest the potential for growth in temperature-abused refr igerated foods.