The intestinal flora of colonization-resistant mice

Abstract

SUMMARYTo facilitate the isolation of anaerobes from cultures in which swarming organisms were present Roux flasks were adapted to provide anaerobic conditions. Using these flasks, five species of anaerobes were isolated from the caecum of mice resistant to colonization with Escherichia coli and other Gram-negative organisms. These species accounted for the majority of organisms seen in films of caecal material. No aerobes were isolated and the flora of these mice apparently consisted of a limited number of anaerobes representing part of the intestinal flora of conventional mice. Three of the species were clostridia and another was identified as Propionibacterium acnes. One species resembled Catenabacterium but was not identified. One of the Clostridium species could only be isolated when the medium was supplemented with yeast extract and vitamins. This species sporulated on media with ammonium phosphate as the source of nitrogen; tryptone completely suppressed sporulation.

Colonization resistance of the digestive tract in conventional and antibiotic-treated mice

“…Studies of the caecal flora of the offspring of germ-free mice contaminated with these anaerobes (CRF-mice) show that five species are represented. Lactobacilli and Bacteroides, the predominant anaerobes of conventional mice, are absent and the major constituents are tapered rods belonging to the genus Clostridium (Wensinck & Ruseler-van Embden, 1971). The inability of lactobacilli and Bacteroides to reduce coli populations in gnotobiotic mice (Schaedler et al 1965) supports the view that in conventional animals CR is also induced by one or more of the five anaerobes present in CRF-mice.…”

“…The normal flora has been shown to accelerate the propulsion of gastro-intestinal contents (Abrams & Bishop, 1966, 1967, to reduce the volume of the caecum characteristically enlarged in germ-free and antibiotic-treated animals (Savage & Dubos, 1968; Waaij, 1969) and to produce volatile acids which are thought to inhibit the multiplication of Salmonella in the large bowel (Meynell, 1963;Bohnhoff, Miller & Martin, 1964a, b). In this respect it is important to note that the caecum volume of CRF-mice is normal and that the anaerobes isolated produce several volatile acids in vitro (Wensinck & Ruseler-van Embden, 1971). It is unlikely that the immune system contributes to CR: both the high values in CRF-mice, born and raised in the germ-free isolator, and the immediate drop of CR in conventional animals after the onset of antibiotic treatment, are difficult to explain when CR is supposed to be antibody-dependent.…”

“…For convenience, these mice are called CRF-mice. Their intestinal flora, which consisted of anaerobic bacteria only, was subjected to a detailed study to be reported separately (Wensinck & Ruseler-van Embden, 1971). …”

The faecal flora of patients with Crohn's disease

“…From the final dilution ofthe stool sample, 0 1 ml was plated in anaerobic culture flasks (Wensinck & Ruseler-van Embden, 1971). The following non-selective medium was used: tryptone (Oxoid), 15 g; glucose, 5 g; soluble starch, 1 g; yeast extract,3 g; meat extract (Oxoid), lOg; K2HPO4 .3H20,3 g; KH2PO4,0 5 g; NaCl, 5 g; MgSO4.…”

The influence of media on the recovery of bacteria from the normal mouse caecum

“…The other media yielded higher counts with not much difference between them. This suggests that the vitamins included by Wensinck & Ruseler-van Embden (1971) could be omitted. The haemolysis or the replacement of sheep blood by an erythrocyte extract (Hazen berg et ai.j 1981) or rumen fluid (Roach & Tannock, 1980), was no advantage in attempting the recovery of mouse caecal anaerobes.…”