I'm a little reluctant to help push EPA's cause du jour, but I agree that the abuse of prophylactic antibiotics, both in human medicine, and in factory farming is a big problem:
Antibiotics, hormones increasingly found in livestock and poultry manure
Growing scientific evidence shows that pathogens, antimicrobials and hormones are increasingly appearing in livestock and poultry manure across the United States, according to a literature review prepared by the U.S. Environmental Protection Agency (EPA).Modern antibiotics revolutionized medicine in the second half of the last century, saving countless lives. However, increasingly, microbes have become immune to them, leading to diseases like MRSA (methecillin resistant Staphylococcus aureus infection) which are difficult to cure. We are in serious danger of losing our ability to fight infectious diseases. There is no reasonable doubt that the overuse of antibiotics both in human medicine and animal farming have contributed to the problem. Stopping this abuse, and preventing it in the future with new antibiotics is one of the most important gifts that we could give to upcoming generations
These “contaminants of emerging concern”—so named because their risks to human health and the environment may be unknown—could pose threats to plants, animals and people if rain, spills or storage failures push contaminated manure into rivers and streams.
...Manure can contain pathogens, for instance, that could infect humans if allowed to contaminate our drinking water or food crops. It can contain antibiotics and vaccines that could facilitate the development of antimicrobial resistance. And it can contain natural and artificial hormones that, even in low concentrations, could affect the reproductive health and fitness of fish, frogs and other marine life.