Antimicrobial drugs in veterinary medicine have made a dramatic improvement in the health of our horses, but it's alarming when infections do not respond to these drugs. "It is not a new phenomenon, but there has been ever-growing concern about antimicrobial resistance," said Josie Traub-Dargatz, DVM, MS, Dipl. ACVIM, of Colorado State University, in her presentation at the AAEP Convention. (See article #4047 online.)

The frequency of treatment failure in equine patients due to antimicrobial resistance is unknown because there is no national system to monitor resistance of animal pathogens. However, there are documented cases of resistant infections in horses, and many reasons why veterinarians should be concerned about the issue.

Traub-Dargatz said veterinarians should be concerned about this issue because it is unlikely that any new antimicrobials will arrive on the market for veterinary use in the near future.

"There hasn't been a new class of antimicrobial since the '80s," she said. "The cost to bring a new drug to human practice is estimated at $300 million