Comparison of Escherichia coli from bacteriuric patients with those from feces of healthy schoolchildren.

The properties of 709 strains of Escherichia coli isolated from feces of healthy schoolchildren were compared with those of 115 strains from the urine of girls with asymptomatic bacteriuria (ABU) detected in a screening program. These fecal strains were also compared with 45 strains that caused asymptomatic reinfections and 10 that caused symptomatic reinfections in the same group of girls. Typing of O antigen was done by direct bacterial agglutination, and K typing was done with a serum agar technique. Hemolytic capacity was assessed in solid medium. Sensitivity to the bactericidal effect of normal serum and minimal inhibitory concentrations of ampicillin were also determined. The strains isolated from girls who had reinfections of ABU were found to be a random sample of the fecal flora, but the strains from children with symptomatic reinfection were not. Strains from index patients with ABU differed from the other groups in a way that was indicative of adaptive changes in the structure of cell envelopes.