A study into the genotypes of Escherichia coli from pyometra affected dogs

Abstract

Pyometra is one of the most common reproductive diseases in female intact dogs. It affects nearly 25% of all intact female dogs before they reach 10 years of age. This disease not only affects the animal’s health but also its breeding value. The predominant pathogen that has been isolated from dogs with pyometra is Escherichia coli (E. coli). The research described in this thesis focused on characterising the particular strains found in dogs affected by pyometra and comparing them with those found in the rectum of control dogs. The objectives were to identify differences regarding the genotype, the presence of genes transcribing for uropathogenic virulence factors (UVF) and the bacteria’s abilities to form biofilms. The initial aim of investigating differences between bacteria isolated from young and old pyometra patients was hindered by the limited availability of E. coli strains from young dogs. To achieve these aims uterine, vaginal and rectal samples were collected from 32 pyometra patients and the patients’ age was recorded. Rectal samples were collected from 45 clinically healthy dogs to serve as controls. Samples were analysed by polymerase chain reactions for genotyping by Clermont’s scheme and evaluation of UVF gene presence. A subset of samples was further investigated to analyse their biofilm forming potentials using crystal violet assays. Finally, the ability of biofilm producing bacteria to withstand antimicrobial treatment was evaluated using assays to determine the minimum inhibitory concentration and time-kill curve studies. These investigations demonstrated that there is a significantly different UVF gene profile in E. coli isolated from pyometra patients when compared to control dogs. In contrast, there were only few differences between the uterine, vaginal and rectal samples taken from the same dogs. Similarly, little difference was detected between phylogenetic groups with the majority of all samples being classified as B2. Isolates with strong biofilm forming potential were only identified from those collected from pyometra patients but not control dogs and they were subsequently shown to be more resistant to antimicrobials. These studies have shown that there are major differences between the E. coli strains present during pyometra and those present as part of the normal microflora in the intestinal tract. It is also the first time that the biofilm forming potential was evaluated for bacteria involved in pyometra. It becomes apparent that care must be taken in the medical treatment of pyometra patients to consider the impact of biofilms on their efficacy.