http://www.nature.com/news/2005/051031/full/051031-5.html New drugs are developed based on naturally occuring antibiotics present for instance in sweat and mucus. It was (naively) thought that these natural antibiotics were better then the ones we have now because microbes wouldn't be able to develop resistance to them. They tested on now. And guess what? Microbes do develop resistance for them. They haven't done so far, because in the natural situation the microbe is killed fast and attacked with a whole diverse set of antibiotics. Obviously that doesn't mimic the situation of medical use of drugs researched based on these natural antibiotics. Needless to say researchers are worried about this development. If we let these drugs out and microbes do develop a resistance against them the next time you have a simple cut in your skin you might find yourself in the situation that this little cut doesn't heal. Let me predict that these new drugs based on naturally occuring antibiotics in our body WILL be released. There is after all a profit margin to be looked after.