A bioreactor system to study survival of Salmonella Typhimurium in pig gut content

Abstract

The batch culture system included six bioreactors. Three bioreactors containing stomach slurry were maintained at pH 4,5 and 6 respectively. Bioreactors containing small intestine slurry were maintained at pH 5,6 and 7 respectively. The bioreactors were inoculated with 10 ml of viable Salmonella. The bioreactors were maintained for 6 hours. Samples of 10 ml were taken at 0 time and at 1, 2, 4 and 6 hours. The samples were analysed for the presence of Salmonella and SCFA. In the stomach samples Salmonella numbers increased at pH 6 but fell at pH 4. In the small intestine sample Salmonella numbers increased at pH 6 and 7. In terms of SCFA production, in the stomach, with samples at pH 6 there was little change in the amounts of lactate, succinate and formate to that detected at 0 time, however levels of acetate did increase slightly. In the small intestine samples levels of succinate and formate increased slightly up to 4 hours, levels of acetate increased significantly from 0 to 6 hours. In terms of the specific growth rates of the individual strains, both strains grew at pH 6 in the stomach content and to a greater extent in the small intestinal content. A bactericidal effect was observed at pH 4 in the stomach content while neither killing nor growth occurred at pH 5 either in the stomach or the small intestine content. Both strains grew well in the small intestine content at pH 7, showing generation times of up to 24 min.