Penicillin, accidentally discovered by Alexander Fleming in 1928, revolutionized the treatment of deadly diseases. But even Fleming suspected its danger. In the summer of 1928, Scottish physician Alexander Fleming returned from vacation to his laboratory at St. Mary's Hospital in London and accidentally discovered a mold in a Petri dish that could apparently kill even the most hardy germs. Fleming called the fungus "penicillin." He hoped it would help him achieve his vision of a drug that would only attack pathogens, not the body’s healthy cells. It would take two decades and a world war before Fleming and others succeeded in producing the antibiotic in such quantities that the epidemics of the time - typhus, syphilis, gangrene, tuberculosis - could be eradicated. But Fleming suspected the medical breakthrough might one day prove catastrophic. The problems began with the first use of penicillin as a mass drug in the Allied offensive against Hitler’s Germany in 1944. After the war, penicillin could even be purchased in US pharmacies as chewing gum for a sore throat. In occupied Germany and Austria, unscrupulous smuggler bands exploited a ban on penicillin by selling stolen and counterfeit products. Today, an estimated 70 percent of aggressive germs are now penicillin-resistant and hospitals have long been on red alert.