Proper Use of Antibiotics for Uterine Infections (AAEP 2011)

Treating a broodmare's uterine infection properly can mean the difference between her conceiving or staying empty this season. Proper treatment also can determine whether or not you contribute to antibiotic resistance; development of "superbugs" is a genuine concern in not only the human medical but also the veterinary community. Accomplishing both can be complex, according to one veterinarian who described endometritis treatment approaches at the 2011 American Association of Equine Practitioners convention.

"The decision to use antibiotics for the treatment of a reproductive problem in mares is not always clear-cut or cookbook," said John Dascanio, VMD, Dipl. ACT, ABVP (Equine), associate professor of Large Animal Clinical Sciences at the Virginia-Maryland Regional College of Veterinary Medicine. "One of the key factors in treating endometritis is to ensure that a bacterial infection that will respond to antibiotics is actually present." Dascanio discussed how and when to treat endometritis with systemic or local antibiotics to a veterinary audience at the convention, which was held Nov. 18-22 in San Antonio, Texas.

In some chronic endometritis cases, the infection can be deep-seated in the uterine lining and some antibiotics will not penetrate deep enough into the wall of the uterus if the mare is only treated with an intrauterine infusion of antibiotics (i.e., "washing" the uterus).

"In some cases, intrauterine antibiotics are not sufficient and systemic antibiotics administered either intravenously or intramuscularly are needed," noted Dascanio.

According to Dascanio, veterinarians should consider multiple factors when treating uterine infections, such as:

  • The presence of an overwhelming number of bacteria;
  • Uterine fluid and debris that could potentially inhibit antibiotic activity;
  • Whether systemic or local (intrauterine) antibiotics would be best;
  • What type of killing activity the antibiotic has (time- or concentration-dependent killing);
  • Dose and length of treatment period;
  • Lack of uterine contractility to help clear the infection (the uterine naturally contracts to help express fluid, debris, and/or infection within; certain drugs can assist with this process); and
  • Lack of cervical dilation that might prevent uterine clearance.

According to Dascanio, some of the big "no-nos" when it comes to treating endometritis include mixing β-lactam and aminoglycoside antibiotics in intrauterine infusions, using high concentrations of iodine when flushing the uterus, and treating mares with intrauterine antibiotics less than four hours postmating. Dascanio explained that mixing antibiotics has the potential to render them less effective. Using higher concentrations of iodine may be harmful to uterine lining, he said, and treating with antibiotics less than four hours postmating can harm the spermatozoa, thus decreasing fertility.

"Veterinarians should base antibiotic therapy on sensitivity testing and consider alternatives to antibiotics such as proper breeding management and other techniques, such as the use of uterine lavage and augmenting uterine contractions, to minimize the use of antibiotics while still successfully treating the patient," advised Dascanio.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.