Increased expression of type-1 fimbriae by nonpathogenic Escherichia coli 83972 results in an increased capacity for catheter adherence and bacterial interference

Abstract

Background. In vitro, urinary catheter colonization by avirulent Escherichia coli 83972 impedes subsequent catheter colonization by a variety of uropathogenic organisms. However, E. coli 83972 shows a low efficacy of adherence to silicone urinary catheter material, possibly because the fim operon encoding adhesive type 1 fimbriae is incomplete. We hypothesized that improving the catheter adherence of E. coli 83972 would improve its bacterial interference properties. Methods. We created adhesive mutants by transforming wild-type E. coli 83972 with fim+ plasmids. Adherence to urinary catheters and ability to prevent uropathogenic E. coli from colonizing urinary catheters were studied by use of a sonication assay. Results. The addition of a single-copy fim+ plasmid increased adherence to urinary catheters 10-fold, and addition of an 18-copy fim+ plasmid increased adherence 100-fold. The more adherent 18-copy fim+ plasmid strain was more effective at blocking catheter colonization by pathogenic E. coli than was the wild-type parental strain. Neither Δfim nor fim+ E. coli 83972 adhered to shed urinary epithelial cells. Conclusions. Our results indicate that improving urinary catheter adherence augments the bacterial interference capabilities of benign E. coli 83972. Increased expression of type-1 fimbriae may enhance bacterial interference without conferring virulence on E. coli 83972. © 2008 by the Infectious Diseases Society of America. All rights reserved.