Great article in the NYTimes about different approaches to protecting farm animals and people from infection and intoxication by e. coli O157:H7. The most promising approach seems to be a vaccine made from a protein and the polysaccharide coating found on wild e. coli bacteria.
Whether food is produced by your local CSA or a humongous factory farm, it can become contaminated by e. coli. and O157:H7 is the nastiest variant of the lot. So a universally prescribed vaccine against it would be good news indeed.