Antimicrobial use in animal feed an ecological and public health problem.

A ntibiotics arguably constitute one of the most important medical discoveries of the last century. Unfortunately, many antibiotics now are rapidly losing effectiveness as bacteria increasingly acquire resistance to multiple medicines. Antibiotic use is the key driver of resistance. Even with appropriate antibiotic use, some resistance will inevitably develop. Misuse and overuse of antibiotics, however, hasten and spread resistance. Concerns about antibiotic overuse in human medicine are widespread and well founded. In 1998, an Institute of Medicine report determined that between 25 percent and 40 percent of antibiotic use in U.S. hospitals is unnecessary, as is 20 percent to 50 percent of physician use in community settings. 1 Increasing resources have been devoted to changing prescribing practices as well as patient expectations. In contrast, routine feeding of antibiotics to animals raised for food has only belatedly attracted the medical community's atten-tion—despite last year's editorial in Science stating the " strong scientific consensus " that routine administration of antibiotics to food animals is " a bad idea. " 2 Agricultural Uses Antimicrobials have a variety of uses in agriculture. (Antibiotic refers to an agent produced by microorganisms that inhibits or kills other microorganisms, while an-timicrobial is a broader and perhaps more accurate term that also includes agents of semisynthetic or synthetic origin). They are appropriately given to livestock and poultry as therapy for infection. Antimi-crobials are also given prophy-lactically to entire groups of nondis-eased animals, typically during periods of high risk for future infection such as after weaning or transport. For decades, antimicrobials have also been given to food animals routinely in feed or water— over longer periods of time and in