The capacity of 453 Escherichia coli strains to agglutinate erythrocytes and yeast cells and to attach to human urinary tract epithelial cells was tested. The strains were isolated from the urine of patients with acute pyelonephritis, acute cystitis, or asymptomatic bacteriuria and from the stools of healthy school children. Three main patterns of hemagglutination were found: (i) mannoseresistant agglutination of human erythrocytes alone or simultaneously with mannose-sensitive agglutination of guinea pig erythrocytes: (ii) only mannosesensitive agglutination of guinea pig and other erythrocytes; and (iii) no agglutination. Strains with mannose-resistant agglutination of human erythrocytes alone or in combination with mannose-sensitive hemagglutination attached in high numbers to human urinary tract epithelial cells. Bacteria inducing only mannosesensitive hemagglutination attached in low numbers, and non-agglutinating strains did not bind to the urinary tract epithelial cells. The bacterial surface antigen(s) mediating mannose-resistant hemagglutination of human erythrocytes and attachment to human urinary tract epithelial cells may be one factor selecting for E. coli from among the fecal flora which infect the urinary tract. The highest proportion of strains with this property was found among acute pyelonephritis isolates (77%), and the lowest proportion of strains with this property was found among normal fecal E. coli (16%).

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Bacterial factors associated with long-term persistence in the colon have not been defined. Individual Escherichia coli strains in the colonic flora of 13 schoolgirls with asymptomatic bacteriuria were identified by electromorphic typing of chromosomally encoded enzymes and defined as resident or transient. The strains were characterized as to serotype, receptor specificity, and adherence to the human colonic epithelial cell line HT-29. Colonic resident strains expressed P fimbriae, adhered to colonic epithelial cells via a mannose-resistant mechanism, and expressed the uropathogenic serotypes O1, O2, O6, O7, O18, O25, or O75 more often than did the transient strains, which were often nontypeable. The serotype and hemagglutination pattern were generally retained during intestinal carriage, in contrast to the loss of such properties upon prolonged colonization of the urinary tract. P fimbriae with Gal alpha 1----4Gal beta-specific adherence may, in fact, have evolved to increase persistence in the colon.

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The role of bacterial adherence in the persistence of bacteria in the human urinary tract was analyzed. Women with chronic symptomatic urinary tract infections were subjected to deliberate colonization with nonvirulent Escherichia coli, after eradication of their current infections. E. coli organisms were instilled into the bladder through a catheter. The strain used for colonization, E. coli 83972, was isolated from a patient with stable bacteriuria. It lacked expressed adherence factors and did not belong to the uropathogenic O:K:H serotypes. Strain 83972 was transformed with the pap and pil DNA sequences encoding Galcl-4Galpand mannose-specific (type 1) adhesins. Patients were colonized with a mixture of the wild-type and the transformed strains. E. coli 83972 caused stable bacteriuria for >30 days in 7 of 12 individuals. In contrast, the Galal-4Galjp-recognizing or mannose-binding transformants were eliminated within 48 h. The consistent superiority of the wild-type strain in establishing stable bacteriuria when compared with the adhesive transformants did not appear to be due to differences in growth rates or to plasmid segregation. Rather, the transformants expressing the adhesin determinants were selectively eliminated by the host. This suggested that the acquisition of adherence factors is not sufficient to increase the fitness of E. coli for survival in the urinary tract of humans.