Endometritis, an inflammation of the endometrium (the inner lining of the uterus), is one of the leading reasons for poor pregnancy rates in mares. It has several causes, including infectious organisms and a mare’s inability to clear debris from her uterus after breedeing.

Bacterial endometritis associated with Escherichia coli can be particularly challenging to treat due to the bacteria’s ability to adapt in the face of treatment and the wide range of antimicrobial resistance (ranging from highly susceptible to highly resistant) observed. Jennifer Morrissey, DVM, a resident at Colorado State University’s Equine Reproduction Laboratory in Fort Collins, decided to see if she could differentiate between types of E. coli based on genetic grouping and correlate these differences with antibiotic resistance and biofilm formation.

She presented the results of her preliminary study at the 2016 Theriogenology Conference, held July 27-30 in Asheville, North Carolina.

Escherichia coli is one of the most common bacteria isolated from the equine uterus, representing 30-50% of all cases of infectious endometritis,” Morrissey said.

E. coli has adapted into many different pathotypes, with each pathotype having undergone unique changes to allow the bacteria to thrive in a specific area. For example, she explained, in human medicine the E. coli that cause gastrointestinal disease are different from the E. coli that cause urinary tract infections.

In her study, she used genetic grouping to categorize 78 E. coli isolates collected from the reproductive tracts