New adherent form of an attaching and effacing Escherichia coli (eaeA+, bfp-) to the intestinal epithelial cells of chicks

The adherent site of ''attaching and effacing Escherichia coli'' (AEEC; O103: H-, SK-1 strain) on the intestinal epithelial cells of chicks infected naturally and experimentally was ultrastructurally investigated. The eaeA gene was detected by polymerase chain reaction in the SK-1 strain of E. coli isolated from the intestinal content of a chick infected naturally, however, the bundle-forming pilus gene could not be detected. The SK-1 strain (bfp-) of AEEC could attach to the intestinal epithelial cell and induce attaching effacing lesions in the intestine of chicks. Transmission electron microscopy revealed numerous pilus-like microfilaments in the space between colibacilli and the membranes of the intestinal epithelial cells. The present study suggests that SK-1 strain (eaeA+, bfp-) may attach closely to the intestinal epithelial cells by a novel adhesin different from bfp.