Investigation of a Providencia rettgeri strain that has enterobacterial common antigen in the immunogenic state

Antigenic material obtained by phenol-water extraction from Providencia rettgeri strains, Escherichia coli O:14 strains, and mutants of the E. coli O:14 strain were examined by the passive (indirect) hemagglutination technique, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and by immune blotting (lipopolysaccharide (LPS) blotting). Providencia rettgeri 965, like E. coli O:14, was demonstrated to have an enterobacterial common antigen (ECA) in the immunogenic form but, unlike E. coli O:14, it possessed characteristics of a smooth strain. Two populations of molecules were observed to occur in P. rettgeri 965 phenol-water extracts: one consisting of LPS identifiable with specific O antisera and the other of ECA molecules identifiable with E. coli O:14 antiserum or with a monoclonal antibody against ECA.