'Normalization' of germfree mice with anaerobically cultured caecal flora of 'normal' mice

Germfree (GF) mice were inoculated with a cultured flora from 10(-1), 10(-3), 10(-5), and 10(-7) dilutions of caecal contents from a 'normal' mouse. GF mice associated with a flora of a 'normal' mouse served as controls. The following intestinal parameters were determined: Colonization resistance (CR), Relative caecal weight (RCW), villus:crypt ratio (jejunum and ileum), IgA-producing cells (jejunum and ileum), beta-aspartyl glycine (faeces), volatile and non-volatile fatty acids (caecum) and bile acids (faeces). Only the 10(-1) culture was able to induce similar changes in the GF mice to a 'normal' flora. The GF + 10(-5) and GF + 10(-7) groups deviated markedly from the controls while the GF + 10(-3) group showed in general intermediate values between GF + SPF and GF + 10(-1) on the one hand and GF + 10(-5) and GF + 10(-7) on the other hand. beta-aspartyl glycine was present only in the GF + 10(-7) group. Scanning electron microscopy (SEM) of ileal contents revealed segmented filamentous organisms in the ileum of controls and the GF + 10(-1) group. The faecal flora consisted mainly of fusiform organisms. In the faeces of the 10(-5) and 10(-7) groups increasing amounts of non-bacterial matter were found, while in the faeces of the other groups virtually only bacteria were seen.