K antigen determination of Escherichia coli by counter-current immunoelectrophoresis (CIE)

The application of the counter-current immunoelectrophoresis (CIE) for determination of E. coli acidic polysaccharide K antigen is described. The most appropriate dilutions of antigens and antisera were established after examination of six different K antigens with homologous OK antisera. According to this result all test strains for acidic polysaccharide K antigens, i.e. K1 to K57, K62, K74, K82, K53, K84, K92, K93, K94, K95, K96, K97, K98 and K100, were examined and OK antisera suitable for the CIE test were selected. The following reciprocal cross-reactions were found: K2 and K62; K7 and K56; K12 and K82; K13, K20 and K23; K18 and K22; K16 and K97, and K53 and K93. The CIE method is now used as a routine test in our laboratory.