Survival of Bacillus cereus spores and vegetative cells in acid media simulating human stomach

Abstract

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 1AE0-5AE2, and on vegetative cells at pH 2AE5-5AE7. 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 1AE0 and 1AE4, 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 2AE0 log CFU ml )1 in 2 h) in vegetative cell counts was observed at pH below 4AE2, 4AE0, 3AE6 and 3AE5 in GM-chicken, GM-JB, GM-milk and GMpea soup, respectively. Between pH 5AE0 and 5AE3, B. cereus growth was observed in GM-JB (1AE2 log CFU ml )1 increase after 4 h) and in GM-pea soup (1AE8 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.

Low Concentrations of Bile Salts Induce Stress Responses and Reduce Motility inBacillus cereusATCC 14570

“…The reference RNA was pooled from four different experiments. This strategy permitted observation of the transcription trends of each gene for three time points (15,30, and 60 min) in the bile salt and control cultures. The reason for doing this was that there were significant changes in the growth rates of the two cultures and that after 30 and 60 min of growth the cell density in the control was approximately double that of the bile salt culture.…”

Effect of probiotic bacteria on antiradical activity of peptides isolated from dry-cured loins

“…The process of gastrointestinal digestion was carried out according to the method of Clavel, Carlin, Lairon, Nguyen-The and Schmitt (2004) and Marteau, Minekus, Havenaar and Huis (1997). A sample of ground dry-cured loin (30 g) was mixed with 150 mL of buffer P (phosphoric buffer with 1% of pepsin from porcine gastric mucosa [0.7 FIP-U/mg] at pH 2.4 ± 0.2) and was incubated in a shaker at 37°C for 2 h. The sample was then mixed with PA buffer (50 mL of phosphate buffer with bile salts at pH 7.0 ± 0.2 and 1 Kreon 25,000 tablet containing 300 mg of pancreatin with the following enzyme content: 25,000 Ph.…”

A quadruple-enterotoxin-deficient mutant of Bacillus thuringiensis remains insecticidal

“…In contrast, we obtained the hbl a2 deletion with the pBKJ236/pBKJ223 system. Our work illustrates an (Hansen & Hendriksen, 2001;Guinebretière et al, 2002;Moravek et al, 2006;Fagerlund et al, 2007), and the pathogenic potential of a particular strain probably results from many factors, including the number of bacterial cells ingested, the number and type of enterotoxins present, the levels of enterotoxin expression, the type of food in which they are ingested, the degree of stomach acidity, the concentration of bile and the composition of the gut microbiota (Clavel et al, 2004(Clavel et al, , 2007.…”