[AustinScript]

I don't see a peer reviewed study but it does appear to be the FDAs position :

"Bacteria evolve to survive threats to their existence. In both humans and animals, even appropriate therapeutic uses of antibiotics can promote the development of drug resistant bacteria. When such bacteria enter the food supply, they can be transferred to the people who eat food from the treated animal."

I suggest reading the article to really understand what they are saying rather than dissecting the little tidbit I picked out but it sounds as if it doesn't matter if the exact same drug is used to treat both humans and animals, there is still a threat.