Using enzyme-linked immunosorbent assay to detect Escherichia coli K88 pili antigens from clinical isolates

Colonization of the small intestine is a prerequisite for enterotoxigenic Escherichia coli (ETEC) to cause diarrheal disease. Colonization is dependent on the capability of ETEC to adhere to the villous epithelium of the small intestine. This adherence attribute is conferred by pili structures produced by ETEC. The present study compares the efficiencies of the standard agglutination test, Y-1 mouse adrenal cell test, and infant-mouse gastric test with the efficiency of the enzyme-linked immunosorbent assay (ELISA) for the detection of the K88 pilus antigen and enterotoxin-producing E coli. The ELISA, a double antibody sandwich assay utilizing specific anti-K88 pilus antiserum, was used. Identification of isolates from clinical samples was accomplished on suspensions of bacteria. The sensitivity of the assay was in the nanogram per milliliter range, as determined by measuring purified pili. Results could be determined visually, but quantitative results indicated a positive optical density to negative optical density rate of 1.9 to greater than or equal to 3.0 on samples submitted to a clinical laboratory. The development of this assay indicates the application of such an ELISA for rapid identification of ETEC possessing K88 pili.