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 o f the microbial population of the contents of the porcine ileum has be en developed. The system was tested over the pH range 6.0-8.5, anaerob ically and at dissolved oxygen concentrations within the ranges detect ed in the ileum of piglets at weaning (50 and 100 mu mol l(-1)). The r esults demonstrated that changes in pH and dissolved oxygen within the se ranges had relatively little effect on the total numbers of aerobic and anaerobic bacteria. Lactic acid bacteria, enumerated anaerobicall y, showed changes in viable counts in response to pH changes but were apparently unaffected by changes in dissolved oxygen, although the pro portion of aerotolerant species within this group was increased at hig h concentrations of dissolved oxygen. The relative proportions of lact obacilli and coliforms were similar to those reported in vivo when dis solved oxygen was present at a concentration of 50 mu mol l(-1). Under these conditions the simulated population was consistently found to r esist colonization by an enterotoxigenic Escherichia coli, of a seroty pe known to cause weaning scours in the piglet.