Test tubes filled with samples of bacteria to be tested are seen at the Health Protection Agency in north London March 9, 2011. Picture taken March 9, 2011. For decades scientists have managed to develop new medicines to stay at least one step ahead of the ever-mutating enemy, bacteria. Now, though, we may be running out of road. Methicillin-resistant Staphylococcus aureus, commonly known as MRSA, alone is estimated to kill around 19,000 people every year in the United States -- far more than HIV and AIDS -- and a similar number in Europe, and other drug-resistant superbugs are spreading. Picture taken March 9, 2011. To match Special Report ANTIBIOTICS/ REUTERS/Suzanne Plunkett (BRITAIN - Tags: HEALTH SCI TECH)