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.