Can DNA Testing Lead to Better Endometritis Treatments?

Can DNA Testing Lead to Better Endometritis Treatments?

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

Photo: Anne M. Eberhardt/The Horse

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 of horses in Lexington, Kentucky, and test their susceptibility to antibiotics. She found that most of the isolates could be classified genetically as phylogroup B1 or B2 (47 and 21 isolates, respectively), with the remaining isolates belonging to group A or E (7 and 3 isolates, respectively).

She tested the isolates’ antibiotic resistance to gentamicin, enrofloxacin, ceftiofur, amikacin, ampicillin, trimethoprim sulfamethoxazole, ticarcillin with clavulanic acid, and penicillin and also looked at their ability to form biofilms in vitro (in the lab)—communities of bacteria that act synergistically to provide antibiotic resistance.

She found that the two E. coli groups responded to the various antibiotics differently, but that, overall, B2 had greater antibiotic resistance than B1. B1, however, had a higher ability to form biofilms in vitro.

Morrissey and her collaborators are planning to perform invasion assays on these isolates to evaluate the pathogenicity (ability to cause disease) of the different phylogroups and whether B1 and B2 isolates result in different pregnancy rates. Morrissey said these results potentially reflect the different behavior of E. coli in clinical settings and could provide insight into diagnostic and treatment options for treating E. coli endometritis.

About the Author

Alexandra Beckstett, The Horse Managing Editor

Alexandra Beckstett, Managing Editor of The Horse and a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as Assistant Editor of its book division, Eclipse Press, before joining The Horse.

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