I've been saying for years that people who are only worried about themselves consuming antibiotics in food are missing the point of why putting antibiotics in animal feed is a bad idea
The likelihood that you will cultivate a strain of bacteria that is resistant to antibiotics by eating food that contains trace amounts of antibiotics is very small. (Not so if you consume hi-doses of antibiotics on a regular basis.) However, feed hundreds of thousands of farm animals prophylatic doses and now you have a hug breeding ground for resistant bacteria. Well, now it appears that the worst has happened.
Five out of 90 samples of retail pork in Louisiana tested positive for MRSA — an antibiotic-resistant staph infection — according to a peer-reviewed study published in Applied and Environmental Microbiology last year. And a recent study of retail meats in the Washington, D.C., area found MRSA in one pork sample, out of 300, according to Jianghong Meng, the University of Maryland scholar who conducted the study. (NYT)
See also this excellent blog that tracks the MRSA phenomenon: Superbug