Nobel Prize Laureate Kary Mullis says,
"When Alexander Fleming first discovered penicillin, his boss, Almoth Roth said bacteria would become resistant to it. It took longer than Roth thought, but it is happening...If you take penicillin, you excrete half of it. It goes down into the sewer in low, sub-clinical doses. It doesn't kill all the things in the sewer, but it definitely makes them start developing a resistance to penicillin. Most antibiotic resistance may not arise in our own bodies but elsewhere."