This PowerPoint presentation talks about that. http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&ved=0CCgQFjAAOAo&url=http%3A%2F%2Fruby.fgcu.edu%2FCourses%2Fndemers%2FScitech%2FFall%252011%2Fantibiotic%2520resist.pptx&ei=24U3UuiqN_L_4AOKp4DQDw&usg=AFQjCNE8NtYDzpPiliDV5KRG4dvF1sqm4g&bvm=bv.52164340,d.dmg&cad=rja