Aim: To estimate the survival of enteropathogenic Escherichia coli after passage through the stomach of young and elderly people.
Methods and results: Using enterohaemorrhagic E. coli O157 and a non-pathogenic laboratory strain, inactivation in a pH range between 1.5 and 4.0 was experimentally quantified. Gastric pH and transport have previously been studied in human volunteers following consumption of a solid meal. Combining all these findings, time series of surviving bacteria were mathematically predicted and subsequently, the predictions were validated with in vitro experiments using a pH-controlled fermentor. On average, 20-80% of ingested E. coli are estimated to arrive in the small intestine without inactivation by low pH. The mean overall gastric passage was similar for young and elderly subjects.
Conclusions: The tested E. coli strains can survive the human stomach with a high probability.
Significance and impact of the study: Survival of E. coli under conditions of changing pH in the stomach may be predicted by batch experiments at constant pH. The effectiveness of the gastric acid barrier strongly depends on buffering effects of food.