Identification and cloning of the genetic determinant that encodes for the K88ac adherence antigen

Strains of Escherichia coli capable of causing diarrhea in young pigs are often able to proliferate in the upper small intestine of the infected animal due to the presence of a specific surface antigen, K88. The genetic determinants for K88 antigen production and the ability to utilize the trisaccharide raffinose (Raf) are carried on a 50-megadalton plasmid. Recombinant deoxyribonucleic acid techniques were used to insert an 8.2-megadalton HindIII fragment carrying the K88ac gene(s) from the K88/Raf plasmid pPS100 into the vector pBR322. At lease six polypeptides encoded by this fragment were expressed in minicells. These polypeptides ranged in size from 18,000 to 70,000 daltons. The K88ac antigenic subunit, which has an apparent molecular weight of 23,500, was identified by immunoprecipitation with staphylococcal protein A as the coprecipitant.