Behavior of Bacillus anthracis Strains Sterne and Ames K0610 in Sterile Raw Ground Beef

摘要

The behavior of Bacillus anthracis Sterne spores in sterile raw ground beef was measured at storage\udtemperatures of 2 to 70°C, encompassing both bacterial growth and death. B. anthracis Sterne was weakly\udinactivated (0.003 to 0.014 log10 CFU/h) at storage temperatures of 2 to 16°C and at temperatures greater\udthan and equal to 45°C. Growth was observed from 17 to 44°C. At these intermediate temperatures, B. anthracis\udSterne displayed growth patterns with lag, growth, and stationary phases. The lag phase duration decreased\udwith increasing temperature and ranged from approximately 3 to 53 h. The growth rate increased with\udincreasing temperature from 0.011 to 0.496 log10 CFU/h. Maximum population densities (MPDs) ranged from\ud5.9 to 7.9 log10 CFU/g. In addition, the fate of B. anthracis Ames K0610 was measured at 10, 15, 25, 30, 35, 40,\udand 70°C to compare its behavior with that of Sterne. There were no significant differences between the Ames\udand Sterne strains for both growth rate and lag time. However, the Ames strain displayed an MPD that was\ud1.0 to 1.6 times higher than that of the Sterne strain at 30, 35, and 40°C. Ames K0610 spores were rapidly\udinactivated at temperatures greater than or equal to 45°C. The inability of B. anthracis to grow between 2 and\ud16°C, a relatively low growth rate, and inactivation at elevated temperatures would likely reduce the risk for\udrecommended ground-beef handling and preparation procedures.