Desorption assay: a functional in vitro test for measuring the adhesion of E. coli on the urinary tract epithelium

A functional test was developed to measure different adhesive properties of various Escherichia coli strains on the urinary tract epithelium. The test is based on initial incubation of everted canine ureteral segments in 2-hr cultures of E. coli (adsorption period), followed by sequential elutions in phosphate buffered saline. The release of bacteria (desorption rate) was measured from each elution by quantitative bacteriology. The function of the desorption assay was tested by showing different adhesive properties of various strains of E. coli. The strains isolated from infected canine urinary tracts showed high adhesion capacities superior to other strains of E. coli from different animal and/or tissue origin. This indicates a selective tissue and animal trophism determined by the strength of mucosal attachment. The test is also a valuable tool for measuring adhesion inhibiting substances in urine. The bulk of the adhesion inhibiting effect was localized in the urine ultrafiltrate.