Evaluating the impact of a systemic treatment protocol on uterine biopsy grade and uterine microbiome in mares with pretreatment Kenney grades of IIB-III

Various treatment strategies have been utilized to correct endometritis in broodmares.

Majority of described treatment protocols involve intrauterine administration of various pharmacologic compounds. One treatment protocol used by one of the co-authors, Dr. James Bailey, in embryo transfer donor mares and mares intended to carry their own pregnancies, involves a regimen of DMSO, antibiotics, and dexamethasone (all systemic treatments) administered at specific times during a course of 8 days. This treatment protocol has been anecdotally reported to produce positive results (successful embryo donors and also carrying their own pregnancies) in mares with uterine biopsy Kenney grades of IIB or III. It was hypothesized that this treatment protocol would: 1) improve Kenney biopsy grades IIB or III; and 2) alter uterine microbiome. Objectives were to evaluate the impact of this treatment protocol on each mare’s: 1) endometrial biopsy grade; and 2) uterine microbiome. Mares (n = 13) with previous uterine biopsy grades of IIB-III were included. Eligibility was determined by first collecting an endometrial biopsy sample. Once mares with biopsies that were graded as IIB-III were selected and a pretreatment uterine microbiome sample was obtained using triple-guarded uterine culture swabs. Two swab samples were obtained from each mare. One swab was utilized for 16s-rDNA microbiome analysis. The other swab was submitted for aerobic and anaerobic bacterial culture. Once the pretreatment samples were obtained, the following treatment protocol began: intravenous administration of 250 ml of DMSO mixed with 750 ml of saline on days 1 and 3 (day 1 being the first day of treatment), a daily, oral antibiotic (Equisul-SDT, sulfadiazine-trimethoprime, 24 mg/kg, Aurora Pharmaceutical, Northfield, MN) on day 4 and continuing through day 8, and finally 80 mg of intramuscular dexamethasone on days 6 and 8 (day 8 was the last day of the treatment protocol). Thirty days after the completion of the treatment protocol, posttreatment uterine biopsies and microbiome swab samples were once again obtained. Results are currently pending (laboratory shutdown due to COVID-19), but will be available for presentation at the Society for Theriogenology conference in July. This study will provide objective data to characterize the impact of this treatment protocol on the endometrial grade and the microbiome of treated mares.

Keywords: DMSO, endometrial microbiome, 16s rDNA, embryo recipient, sulfadiazinetrimethoprim

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.