SURVIVAL OF LACTIC-ACID BACTERIA IN A DYNAMIC-MODEL OF THE STOMACH AND SMALL-INTESTINE - VALIDATION AND THE EFFECTS OF BILE

This study was conducted to validate a dynamic model of the stomach an d small intestine to quantify the survival of lactic acid bacteria and to assess the influence of gastrointestinal secretions. The survival of a single strain of each of the following species, Bifidobacterium b ifidum, Lactobacillus acidophilus, Lactobacillus bulgaricus, and Strep tococcus thermophilus, was measured under physiological conditions (e. g., peristalsis, changes in pH, and changes in concentrations of enzym es and bile) and were compared with data obtained from humans. No sign ificant differences were found between the in vitro and in vivo data, indicating that the model has a predictive value for the survival of t hese bacteria in humans. The survival of these strains of lactic acid bacteria in the gastrointestinal model was investigated under two diff erent conditions in the small intestine: simulation of physiological s ecretion of bile and low bile secretion. Reductions in viability were significantly different between the bacterial species. The dose-respon se effect of bile on the survival of the tested bacteria was significa nt, demonstrating the bactericidal effect of bile salts. This study de monstrates the differences among bacterial species in their sensitivit y to gastric and intestinal secretions.