On receiving the 1945 Nobel Prize in Medicine for discovering penicillin, Alexander Fleming finished his lecture with a warning: ‘There is the danger,’ he said, ‘that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant.’ Antibiotic resistance is now one of the biggest threats to global health, food security and development. It could kill as many as 10 million people a year by 2050.