ANTIBIOTICS have changed what it means to be human. Few of us remember when bacterial infections from a wound, a bout of flu , sex or childbirth could kill anyone, at any time. This constant risk of death was just something we lived with. When antibiotics became common in the 1950s, that ended – and the drugs also opened a new frontier of surgery and therapy for other diseases.

But the bad old days are returning as bacteria evolve to resist antibiotics . Just last week, news …