INHIBITION OF ENTEROTOXIGENIC ESCHERICHIA-COLI BY THE MICROFLORA OF THE PORCINE ILEUM, IN AN IN-VITRO SEMICONTINUOUS CULTURE SYSTEM

An in vitro fermentation system capable of maintaining at least part of the microbial population of the contents of the porcine ileum has been developed. The system was tested over the pH range 6.0-8.5, anaerobically and at dissolved oxygen concentrations within the ranges detected in the ileum of piglets at weaning (50 and 100 mu mol l(-1)). The results demonstrated that changes in pH and dissolved oxygen within these ranges had relatively little effect on the total numbers of aerobic and anaerobic bacteria. Lactic acid bacteria, enumerated anaerobically, showed changes in viable counts in response to pH changes but were apparently unaffected by changes in dissolved oxygen, although the proportion of aerotolerant species within this group was increased at high concentrations of dissolved oxygen. The relative proportions of lactobacilli and coliforms were similar to those reported in vivo when dissolved oxygen was present at a concentration of 50 mu mol l(-1). Under these conditions the simulated population was consistently found to resist colonization by an enterotoxigenic Escherichia coli, of a serotype known to cause weaning scours in the piglet.