Effect of monocontamination of germfree rats by enterotoxigenic coliform bacteria

Abstract Because perorally administered enterotoxigenic coliform bacteria do not become colonized within the small intestine of conventional adult animals, the authors evaluated the germfree rat as a potential animal model of acute or chronic colonization by these bacteria. Intestinal colonization occurred promptly after peroral monocontamination, was most prominent in the ileum, and remained essentially unchanged when assessed at weekly intervals in groups of rats monocontaminated by either toxigenic or nontoxigenic strains of Klebsiella pneumoniae or Escherichia coli . No mucosal adherence was detected either by bacterial counts of mucosal scrapings or by immunofluorescent studies. The toxigenic strains did not undergo any significant loss of toxigenicity after colonization for 1 mo. Intestinal transport of water and sodium was assessed by in vivo marker perfusion; values in rats colonized by nontoxigenic strains were similar, both in the jejunum and ileum, to those in conventional animals. Jejunal transport was either reduced or in secretion throughout the 5-wk study period in rats contaminated with a toxigenic strain of Klebsiella. Ileal transport was also reduced at 1 wk and in secretion thereafter in rats contaminated by a toxigenic strain of E. coli , but jejunal transport did not become abnormal in these rats until the 3rd wk. No specific structural abnormalities that could be attributed to the toxigenic strains were visualized. These observations identify the germfree rat as a practical animal model for investigations concerning the pathophysiologic events during acute or chronic intestinal colonization by coliform bacteria with specific enterotoxigenic properties.