Differences in survival among 13 Listeria monocytogenes strains in a dynamic model of the stomach and small intestine

Abstract

Thirteen Listeria monocytogenes strains were compared for the ability to survive in a dynamic gastrointestinal model. Strains displayed various degrees of susceptibility to gastric acidity; however, strain-to-strain variations became evident mainly after 90 min of exposure (pH 2.0). Cell levels transferred to the intestine depended on initial populations, while reductions during intestinal exposure were relatively small for all strains.

FIG. 1.

Schematic diagram of the dynamic gastrointestinal model used in this study. (A, B) 500-ml Erlenmeyer flasks representing the GC and IC; (C, D) pH meters monitoring the pH in the GC and IC; (E, F, G) peristaltic pumps delivering gastric fluid (flow rate, 0.33 ml/min) in the GC and intestinal fluid (flow rate, 0.33 ml/min) and 2 or 4% bile (flow rate, 0.5 ml/min) in the IC; (H) peristaltic pump transferring the gastric contents (flow rate, 1.1 ml/min) in the IC; (I) shaking water bath stabilized at 37°C.

FIG. 2.

Survival (log CFU/ml [Palcam agar counts]) of individual L. monocytogenes strains and pH values within the GC (37°C) during a simulated gastrointestinal challenge, conducted after inoculation into 100 ml of TSBYE-G and incubation for 4 or 16 h at 30°C. Experiments were conducted in triplicate, and the results are means.