Microbial colonization of rat colonic mucosa following intestinal perturbation.

An allochthonous population of spiral-shaped bacteria was found colonizing the surfaces of the colonic mucosa of rats after they had been given magnesium sulphate (MgSO4)-induced diarrhea. These organisms were rarely seen in normal control rats and were not displaced when the treatment was ceased, remaining associated with the tissue for periods of up to 180 days. Similar bacteria were also found when specific pathogen-free rats, lacking mucosa-associated populations, were inoculated with homogenized rat intestine from conventional animals. Light and electron microscopic observations showed that the organisms were attached to the surface of the colon, orientated at right angles to the tissue, with one end inserted into the microvillus border. This is the first report of long-term colonization, following perturbation of the gut ecosystem, of a site on the gastrointestinal mucosa not normally associated with bacteria. The ultrastructure and mode of attachment of these organisms were very similar to that of spiral-shaped bacteria known to associate with the colonic mucosa in monkeys and man.