Characterization of enterotoxigenic Escherichia coli. Serotypes, enterotoxins, adhesion fimbriae, and the presence of plasmids.

Enterotoxigenic Escherichia coli of human and procine origin were characterized with respect to their O and H antigens, fimbrial antigens, and type of enterotoxin produced. Enterotoxin production was determined by bioassay (infant mice) and enzyme-linked immunoassay (ELISA). The presence of genes coding for the enterotoxins was determined by DNA-DNA hybridization. The number and molecular size of plasmids in the enterotoxigenic strains were determined by gel electrophoresis. Strains with the same serological pattern showed different plasmid profiles and could thereby easily be separated. One strain of porcine origin possessed only one plasmid, but produced both heat-labile enterotoxin and the F4 antigen (formerly K88), which is an unusual combination.