Role of Escherichia coli adhesins in urethral colonization of catheterized patients

Escherichia coli is a major cause of catheter-associated urinary tract infection and frequently colonizes the urethra prior to invading the urinary tract. Bacterial pili, filamentous protein cell surface-associated appendages, have been shown to mediate colonization of epithelial cells. Pili associated adhesins can be detected in vitro by their ability to mediate bacterial hemagglutination of erythrocytes. We have assessed the role of bacterial adhesins in supporting urethral colonization by determining the hemagglutination reactions of 56 E. coli isolates from the urethra of patients with indwelling urethral catheters. The adhesin detected most frequently was the type 1 mannose-sensitive hemagglutinin (43%), and 43% of isolates failed to hemagglutinate guinea pig or human erythrocytes. E. coli hemagglutinins were no more common on urethral isolates from patients that were persistently colonized (E. coli present 70% of the time catheterized), than from those that were transiently colonized (E. coli present 30% of the time catheterized). Analysis of the HA reactions and DNA plasmid profiles of multiple isolates from persistently colonized patients suggested that the E. coli strain colonizing the urethra changed over time. The data suggest that bacterial colonization of the urethra is mediated in part by adhesins and changes over time.