The effect of transcervical uterine manipulations on establishment of uterine infection in mares under the influence of progesterone.

This research article investigates how transcervical uterine manipulations under the influence of progesterone impacts the establishment of uterine infections in mares, concluding that high concentrations of progesterone likely contribute to treatment failure.

Study Design and Procedure

• The study involved four pony mares and used a cross-over methodology, a type of research design where subjects are exposed to several sequences of treatments.
• The mares were treated with progesterone, a hormone that regulates the female reproductive system, to ease the establishment of uterine infections.
• Five days after beginning progesterone therapy, an intrauterine infusion of bacteria known as Streptococcus zooepidemicus was administered. This bacterium is a common cause of endometritis (uterine inflammation) in horses.
• Prior to this bacterial infusion, no bacteria were cultured from the mares’ uteri, indicating the absence of pre-existing infection.

Treatment and Results

• Five days following bacterial infusion, the mares received either an intrauterine infusion of 2 g ampicillin in 50 ml sterile water or sterile water without any antibiotics for three consecutive days. Ampicillin is a type of antibiotic used to treat a variety of infections.
• Ahead of antibiotic therapy, mixed bacterial growths were cultured from endometrial swabbings, demonstrating the successful establishment of an infection.
• After antibiotic therapy, the presence of ampicillin-resistant organisms in endometrial swabbings suggests that the treatment was not completely effective.

Control Group and Conclusions

• A control set of two other progesterone-treated mares received an intrauterine infusion of sterile phosphate buffered saline (a solution that matches the pH and salt concentration of the body) instead of the bacteria. Five days later, mixed bacterial cultures were recovered from these mares’ endometrial swabbings too, implicating the influence of progesterone on the bacterial growth.
• The study concludes that the high levels of circulating progesterone were likely responsible for treatment failure. Hence, when treating clinical situations involving transcervical manipulations, such treatments should not be administered when mares are in diestrus (a phase of the estrous cycle where progesterone levels are typically high).