Differences in antigenicity of Escherichia coli strains isolated from patients with various forms of urinary tract infections.

The antibody amounts to crude O antigens were analyzed using the enzyme-linked immunosorbent assay (ELISA) and the indirect hemagglutination (IHA) technique in 42 sera from 6 rabbits. The rabbits were hyperimmunized with one of the WHO Escherichia coli standard strains O1, O2 or O75. In the antibody assays the O antigens were obtained from E. coli strains isolated from 15 patients with asymptomatic bacteriuria (ABU), from 3 patients with acute pyelonephritis and from the WHO E. coli strains used for the immunization. The strains from the patients belonged to serogroup O1, O2 or O75. Significantly higher IgG and IgM antibody levels were detected with the ELISA when using the O1 and O2 but not O75 antigens from the pyelonephritis and WHO standard strains than when using the antigens from the ABU strains. Using the IHA technique the O1, O2 and O75, IgG and IgM antibody titers against the antigens from the pyelonephritis and WHO standard strains were significantly higher than those against the antigens from the ABU strains. In inhibition experiments the antigens from the strains causing pyelonephritis inhibited the reaction between antigen on solid phase and antibodies in solution much more efficiently than did antigens from strains causing ABU.