Quantitation of effects of subinhibitory concentrations of trimethoprim on P fimbria expression and in vitro adhesiveness of uropathogenic Escherichia coli.

The ability to adhere to and colonize urogenital mucosa is an important virulence attribute of uropathogenic Escherichia coli. This adherence, which appears to be mediated by P fimbriae, may be affected by antibiotics or other agents that affect fimbrial expression. We describe here an enzyme immunofiltration assay to quantitate fimbriation and the application of that technique to measurement of the effects of sublethal doses of trimethoprim on P fimbrial expression. Effects on P fimbriation correlated with effects on the adherence of treated bacteria to cultured T24 bladder carcinoma epithelial cells; i.e., trimethoprim treatment decreased both P fimbriation and bacterial adherence. It was possible to quantitate effects on P fimbriation when type 1 fimbriae were also present. The enzyme immunofiltration assay may be useful for studies on the role of fimbriae in the pathogenesis of bacterial infections, and it may facilitate identification of antimicrobial agents that interfere with bacterial adherence to mucosal surfaces.