Two enterotoxigenic Escherichia coli (ETEC) strains (coded 567/7 and 103) isolated from piglets with neonatal diarrhea were described as producers of a new adhesion (F42). With the use of molecular biology and immunology techniques such as DNA hybridization with probes for F41 and K99 genes and Western-blotting of the superficial proteins of these strains and standard E. coli strains carrying genes for F41 and K99 adhesins, it was demonstrated that this new adhesin either shares extensive genetic and immunological determinants with F41 adhesin or they are the same fimbriae.37869-75