Aerobic uterine isolates and antimicrobial susceptibility in mares with post-partum metritis.

Mixed infections were common in equine metritis. Gram-negative bacteria and enterococci were often associated with resistance to the most frequently used antimicrobials. Potentiated sulfonamides are not an appropriate first choice for mares with metritis. While the combination of penicillin and gentamicin may be an appropriate first-line treatment for some mares, use of amikacin or enrofloxacin instead of gentamicin may be preferential.