The possession of three novel coli surface antigens by enterotoxigenic Escherichia coli strains positive for the putative colonization factor PCF8775.

A possible colonization factor, E8775, has previously been described for enterotoxigenic Escherichia coli strains of serogroups O25, O115 and O167. Re-examination of these strains by immunodiffusion has revealed that the antigenic nature of this factor, renamed putative colonization factor (PCF) 8775, is more complex than was first thought. All the strains of serogroup O25 tested possessed two antigenic components, termed CS4 and CS6, and gave mannose-resistant haemagglutination (MRHA) of human and bovine erythrocytes. Spontaneous variants possessing CS6 only did not give MRHA. Strains of serogroups O115 and O167 had the antigenic components CS5 and CS6, and gave MRHA of human, bovine and guinea-pig erythrocytes. Using immune electron microscopy, the components CS4 and CS5 were identified as fimbriae. No fimbriae were associated with CS6.