Bacteria associated with canine pyometra and concurrent bacteriuria: A prospective study

Canine pyometra is a common and potentially life-threatening reproductive disorder in intact female dogs. This prospective study aimed to (1) investigate the bacterial spectrum and antimicrobial susceptibilities of bacterial isolates from the uterus and urine of dogs with pyometra, (2) assess the clonal relatedness and virulence factors of Escherichia coli isolates from individual dogs, and (3) determine the occurrence of concurrent and persistent bacteriuria or clinical urinary tract infections. Bacterial isolates from 208 uterine and 203 urine specimens collected during pyometra surgery were analyzed. Additionally, follow-up urine specimens were collected from 56 dogs with perioperative bacteriuria. Bacterial growth was detected in 87 % (180/208) of uterine specimens, while concurrent bacteriuria was observed in 33 % (67/203) of cases. In one-third (18/56) of these dogs the bacteriuria persisted, being primarily (15/18) asymptomatic. E. coli was the most common isolate in both uterine (71 %) and urine (81 %) specimens. Notably, altogether 32 distinct bacterial species were identified, with mixed growth in 15 % of the specimens. The vast majority of isolates were largely susceptible to tested antimicrobials. Identification of bacterial species was performed using MALDI-ToF MS, and antimicrobial susceptibility was assessed by disk diffusion. Whole-genome sequencing of 45 E. coli strains from fifteen dogs indicated high genetic similarities within individual dogs, supporting a clonal relationship. In conclusion, canine uteri with pyometra contained a plethora of bacterial species, predominantly E. coli, and antimicrobial resistance was rare. Concurrent and persistent E. coli bacteriuria was commonly caused by the same clone as found in the uterus.