An examination of the O and K specificity involved in the antibody-induced loss of the K88 plasmid from porcine enteropathogenic strains of Escherichia coli.

The heat-labile K88 antigen, a virulence determinant coded for by a transmissible plasmid, was eliminated from enteropathogenic strains of Escherichia coli by passage through media containing antibodies to the heat stable antigens of an Abbotstown (O149:K91,K88ac) strain. The plasmid-curing activity of O149 antisera was not O-antigen specific as O149, O45, O8 and O138 strains of E. coli could be 'cured' of their K88 plasmids by this technique. The curing activity was differentiated from the O-antibody by gel filtration, the O149 antibodies were eluted in the IgM peak while the curing activity was found in the IgG peak. In view of the lack of O-specificity and the absence of K88 antibodies it appears that antibodies to a common heat-stable antigenic determinant were involved in this phenomenon.