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.

Pathogenesis of canine pyometra.

Escherichia coli strains associated with pyometra in 85 of 100 bitches investigated had an affinity for urinary tract epithelium and smooth muscle as well as for progesterone-stimulated endometrium and myometrium. The adherence via K-antigen seemed to be important for colonization of the pathogen during development of pyometra. urinary tract infection was detected in 23 of 32 bitches from which urine specimens were obtained. In these bitches, a strain of E coli identical to the strain in the infected uterus was isolated. It was concluded that subclinical urinary tract infection is associated with pyometra and that the uterus will be infected at early metestrus, when receptors for E coli are developed in the endometrium and myometrium, thus enhancing the colonization of bacteria in the uterus.