Abstract
Summary: Enterotoxigenic strains of Escherichia coli, which belonged to serogroups other than 0 6 and produced colonization factor antigen 11, usually produced only coli surface antigen 3 (CS3) and gave weak mannose-resistant haemagglutination of bovine erythrocytes. A non-autotransfer-ring plasmid, NTP165, from a strain of E. coli 0168.H16 coded for heat-stable enterotoxin, heat-labile enterotoxin and CS antigens. The CS antigens expressed after acquisition of plasmid NTPl65 depended on the recipient strain : a biotype A strain of serotype 0 6. H 16 expressed CS1 and CS3; a biotype C strain of serotype 0 6. H 16 expressed CS2 and CS3; strain K 12 and strain El9446 of serotype 0139. H28 expressed only CS3. An exceptional wild-type strain, E24377, of serotype 0139. H28 produced CS1 and CS3 when isolated; a variant of E24377 which had lostthe plasmid coding for CS antigens produced both CSl and CS3 after the introduction of NTP165.