Attachment Factors Among Enterotoxigenic Escherichia coli from Patients with Acute Diarrhea from Diverse Geographic Areas

Abstract

To cause diarrhea, enterotoxigenic Escherichia coli (ETEC) must initially colonize the small bowel. Different surface structures have been implicated in this initial attachment. Recognized attachment factors include colonization factor antigens I and II (CFA/I and CFA/II) and type I pili. Several methods of detection for each of these factors have been reported. In this study, we screened for the presence of these attachment factors among enterotoxigenic E. coli isolated from 40 patients with acute diarrhea and 40 asymptomatic control individuals and examined their ability to attach to ATCC 407 human intestinal cells in vitro. Of 40 patients with diarrhea, 16 (40%) had enterotoxigenic E. coli isolates which exhibited an attachment trait. Fourteen (35%) of these isolates demonstrated the ability to attach to ATCC 407 cells, whereas only four isolates from asymptomatic controls attached ( P < 0.02). A total of 20% of the patient isolates and 7.5% of the control isolates possessed CFA/I. Only one patient isolate demonstrated CFA/II. Evidence for type I pili was found on 10% of the patient isolates and 12.5% of the control isolates. Attachment to ATCC 407 cells allowed the detection of 87.5% (14 of 16) of enterotoxigenic E. coli isolates with any type of attachment trait. Of the 14 cases demonstrating attachment ability to ATCC 407 cells, 7 did not attach in the presence of mannose. Three of these showed evidence for both CFA/I and type I pili, one showed only CFA/I, and one showed only type I pili. Two of those mannose-sensitive attaching isolates showed no other demonstrable trait. Seven patient isolates showed mannose-resistant attachment. Of these, two were classified as possessing CFA/I, and one was classified as possessing CFA/II. The four remaining isolates could not be classified into any recognized attachment factor category, suggesting that other attachment factors remain to be identified.