Behavior of Bacillus anthracis strains Sterne and Ames K0610 in sterile raw ground beef
Tamplin, ML and Phillips, R and Stewart, TA and Luchansky, JB and Kelley, LC, Behavior of Bacillus anthracis strains Sterne and Ames K0610 in sterile raw ground beef, Applied & Environomental Microbiology, 74, (4) pp. 1111-1116. ISSN 0099-2240 (2008) [Refereed Article]
The behavior of Bacillus anthracis Sterne spores in sterile raw ground beef was measured at storage temperatures of 2 to 70°C, encompassing both bacterial growth and death. B. anthracis Sterne was weakly inactivated (-0.003 to -0.014 log 10 CFU/h) at storage temperatures of 2 to 16°C and at temperatures greater than and equal to 45°C. Growth was observed from 17 to 44°C. At these intermediate temperatures, B. anthracis Sterne displayed growth patterns with lag, growth, and stationary phases. The lag phase duration decreased with increasing temperature and ranged from approximately 3 to 53 h. The growth rate increased with increasing temperature from 0.011 to 0.496 log 10 CFU/h. Maximum population densities (MPDs) ranged from 5.9 to 7.9 log 10 CFU/g. In addition, the fate of B. anthracis Ames K0610 was measured at 10, 15, 25, 30, 35, 40, and 70deg;C to compare its behavior with that of Sterne. There were no significant differences between the Ames and Sterne strains for both growth rate and lag time. However, the Ames strain displayed an MPD that was 1.0 to 1.6 times higher than that of the Sterne strain at 30, 35, and 40°C. Ames K0610 spores were rapidly inactivated at temperatures greater than or equal to 45°C. The inability of B. anthracis to grow between 2 and 16°C, a relatively low growth rate, and inactivation at elevated temperatures would likely reduce the risk for recommended ground-beef handling and preparation procedures.