Survival of Bacillus cereus spores and vegetative cells in acid media simulating human stomach
Article first published online: 26 APR 2004
Journal of Applied Microbiology
Volume 97, Issue 1, pages 214–219, July 2004
How to Cite
Clavel, T., Carlin, F., Lairon, D., Nguyen-The, C. and Schmitt, P. (2004), Survival of Bacillus cereus spores and vegetative cells in acid media simulating human stomach. Journal of Applied Microbiology, 97: 214–219. doi: 10.1111/j.1365-2672.2004.02292.x
- Issue published online: 27 APR 2004
- Article first published online: 26 APR 2004
- 2003/0138: received 21 February 2003, revised 02 October 2003 and accepted 23 March 2004
- B. cereus;
Aims: To determine the fate of Bacillus cereus spores or vegetative cells in simulated gastric medium.
Methods and Results: The effects of acidity on the survival of B. cereus in a medium simulating human stomach content was followed on spores at pH 1·0–5·2, and on vegetative cells at pH 2·5–5·7. Gastric media (GM) were prepared by mixing equal volumes of a gastric electrolyte solution with J broth (JB), half-skim milk, pea soup and chicken. At pH 1·0 and 1·4, the number of spores slightly decreased in GM-JB and GM-pea soup and remained stable in GM-milk and GM-chicken. A rapid marked decrease (always higher than 2·0 log CFU ml−1 in 2 h) in vegetative cell counts was observed at pH below 4·2, 4·0, 3·6 and 3·5 in GM-chicken, GM-JB, GM-milk and GM-pea soup, respectively. Between pH 5·0 and 5·3, B. cereus growth was observed in GM-JB (1·2 log CFU ml−1 increase after 4 h) and in GM-pea soup (1·8 log CFU ml−1 increase after 4 h).
Conclusions: Bacillus cereus spores are very much more resistant to gastric acidity than vegetative cells. This resistance strongly depends on the type of food present in the GM.
Significance and Impact of the Study: Our results suggest that the probability that viable B. cereus cells enter the small intestine, where they can cause diarrhoea, strongly depends on the form of the ingested cells (spores or vegetative cells), on what food they are ingested with, and on the level of stomach acidity.