Epithelial, Mucus and Lumen Subpopulations of Escherichia coli in the Large Intestine of Conventional and Gnotobiotic Rats

Germ-free and conventional rats were dosed per os with two Echerichia coli strains and killed 2 or 5 days after dosing. Two separation methods to separate the intestinal E. coli population into lumen-, mucus- and epithelium-associated subpopulations were compared using traditional quantitative bacteriology and a histochemical method based on staining of cryostat sections with Alcian Blue. The majority of the E. coli cells were situated in the lumen contents. This was the case for the test organisms as well as for the indigenous E. coli. The two separation methods performed similarly. The two E. coli test strains showed a clear difference in colonisation ability. However, the relative distribution of the three different subpopulations was the same regardless of the colonisation ability of the test strain.