Effect of bacteriocin-producing lactobacilli on the survival of Escherichia coli and Listeria in a dynamic model of the stomach and the small intestine.

The survival of Lactobacillus curvatus LTH 1174 (bac ) and (bac ) in combination with Escherichia coli LTH 1600 or Listeria innocua DSM20649 during transit through a dynamic model of the human stomach and small intestine (GIT model) was studied. Furthermore, we determined the digestion of curvacin A during gastro-intestinal transit and the effect of this bacteriocin on microbial survival. Lb. curvatus is rapidly killed in the gastric compartment at pH < 2.0, and less than 0.01% of the cells delivered to the small intestinal compartments were recovered from the ileal compartment of the model. Meat exerted a protective effect against the lethal action of bile against Lb. curvatus. The sensitivity of E. coli to acid depended on the aeration of the preculture and decreased in the order anaerobic > strongly agitated > agitated. Lactic acid and curvacin A enhanced the lethal effect of low pH on E. coli. Accordingly, cells from strongly agitated cultures were killed faster in the gastric compartment of the GIT model than those from agitated cultures, and inactivation was accelerated in the presence of curvacin A. E. coli tolerated the bile concentrations prevailing in the small intestinal compartments of the model. The survival of Listeria innocua in the GIT model was comparable to that of Lb. curvatus. The curvacin A produced by Lb. curvatus LTH1174 (bac+) killed > 90% of the L. innocua within 10 min after mixing of the cultures. Curvacin A was not degraded in the the gastric compartment, and could be detected in the ileal compartment during the first 180 min upon addition of the meal.