Characterization of Escherichia coli strains associated with canine pyometra

The purpose of this study was to characterize E. coli isolates from canine pyometra which were isolated in pure culture. The E. coli strains were obtained in 128 cases, from 143 animals which were submitted to ovariohisterectomy. Biochemical analysis of all strains examined was possible on separation of 10 primary biotypes. The majority of the strains (87.5%) belonged to biotype 9, 1, 13 and 15. Dulcitol was fermented by 93% of all isolates. Haemolysin and colicin production was found in 53.9% and 26.6% of the strains, respectively. Approximately 37% of strains expressed resistance to two or more antibacterial agents. No plasmid was detected in 4.6% of the isolates. Plasmid profiles of all plasmid-containing isolates revealed plasmid bands corresponding to molecular weight ranging from 1 kb to 160 kb. Many of the strains examined had a single plasmid of 110 kb (46.1%), or two plasmids 110:65 kb (18.8%). Both plasmids appearing alone or in combination with other plasmids were detected in 90.1% of isolates with plasmid content. It was established that among haemolytic, colicinogenic and motile strains, the presence of both plasmids was 91.3, 94.1 and 91.4%, respectively. The appearance of both plasmids among dulcitol-positive and raffinose-negative strains was estimated at 88.2 and 88.3%, respectively. In a group of colicinogenic strains the presence of a single plasmid of molecular weight 110 kb was estimated at 5.9%. When both plasmids were present (profile 110:65), the percentage of these strains was 70.6%.