What’s at stake is the effectiveness of antibiotics, essential for surgery, chemotherapy, organ transplants and other medical procedures. Antibiotics were “wonder drugs” when discovered in the past century, starting with penicillin, but it has been known for decades that bacteria evolve to resist the drugs — and that overuse and abuse of antibiotics in human health and agriculture have contributed to the problem. A report by the Centers for Disease Control and Prevention in 2019 urged Americans to “Stop referring to a coming post-antibiotic era — it’s already here.” The study found that deaths because of antimicrobial resistance in the United States had dropped 18 percent since a 2013 report, largely due to improved procedures in hospitals, while pointing to continuing challenges outside health care.