Identification of Escherichia coli K1 antigen

We compared the use of bacteriophage sensitivity, seroagglutination with polyclonal antisera raised in rabbits or horses, seroagglutination with murine monoclonal antibody, and the serum agar precipitin technique for the detection of K1 capsular polysaccharide among clinical isolates of Escherichia coli obtained from blood stream infections. Some E. coli isolates failed to yield agreement among these tests, indicating that reliable detection of K1 antigen may require the use of multiple tests.