Amount and avidity of antibody to Escherichia coli O antigen measured with the ammonium sulphate precipitation technique in children with urinary tract infections.

The antibody amounts and avidities were analyzed in 13 patients with acute primary pyelonephritis, 11 patients with acute primary cystitis, and one with ureterocele and recurrent infections, using the ammonium sulphate precipitation (ASP) technique. The ASP titrations did not discriminate as well between pyelonephritis and cystitis as do the determinations with the indirect hemagglutination technique. The increase of antibody titer and avidity detected by the ASP method in some of the cystitis patients suggested a deeper tissue involvement in some cases resulting in antibodies demonstrable with this technique. Since control patients also showed a somewhat heterogenous antibody response regarding titer and avidity it cannot be excluded that stimulation by Escherichia coli antigens in the gut is detected by the ASP method.