The effects of temperature on the growth and heat resistance of Cronobacter spp.

Abstract

The growth and survival of Cronobacter isolates were examined under incubation at different temperatures, and their thermal death behavior was investigated at high temperature conditions of above 50°C. Seventy three strains isolated from fresh vegetables, dried foods and soil were tested: 28 of Cronobacter sakazakii, 5 of C. dublienensis, 27 of C. malonaticus and 13 of C. turicensis. All Cronobacter strains grew and multiplied predominantly at 35 and 44°C until 16 hours of incubation, but showed poor growth at 15°C, and no growth at 5°C. At 48°C, the bacteria grew slightly during 6 to 8 h-incubation but decreased or were inactivated after 16 h-incubation. The heat resistance of Cronobacter spp. was measured under the conditions of 50, 55, 60, 65 and 70°C. Cronobacter strains survived almost without decrement for 30 min at 50°C, but decreased suddenly and perished completely within 10 to 20 min at 55°C and within 2 - 5 min at above 60°C. Some food materials should be stored below 5°C until the preparation, and dried food including powdered infant milk formula should be utilized immediately after reconstitution and preparation.