Doctors routinely perform procedures that carry an extraordinary infection risk unless antibiotics are used. Chief among them: any treatment that requires the construction of portals into the bloodstream and gives bacteria a direct route to the heart or brain. That rules out intensive-care medicine, with its ventilators, catheters, and ports—but also something as prosaic as kidney dialysis, which mechanically filters the blood.

Next to go: surgery, especially on sites that harbor large populations of bacteria such as the intestines and the urinary tract. Those bacteria are benign in their regular homes in the body, but introduce them into the blood, as surgery can, and infections are practically guaranteed. And then implantable devices, because bacteria can form sticky films of infection on the devices’ surfaces that can be broken down only by antibiotics

Dr. Donald Fry, a member of the American College of Surgeons who finished medical school in 1972, says: “In my professional life, it has been breathtaking to watch what can be done with synthetic prosthetic materials: joints, vessels, heart valves. But in these operations, infection is a catastrophe.” British health economists with similar concerns recently calculated the costs of antibiotic resistance. To examine how it would affect surgery, they picked hip replacements, a common procedure in once-athletic Baby Boomers. They estimated that without antibiotics, one out of every six recipients of new hip joints would die.

Antibiotics are administered prophylactically before operations as major as open-heart surgery and as routine as Caesarean sections and prostate biopsies. Without the drugs, the risks posed by those operations, and the likelihood that physicians would perform them, will change.