WASHINGTON, D.C. — In an ominous message to American Hospital Association members gathered for their annual meeting, the head of the Centers for Disease Control and Prevention yesterday warned that the proliferation of drug-resistant bacteria "really threatens to undermine modern medicine."

Tom Frieden, M.D., said an estimated 15,000 Americans die each year of Clostridium difficile alone, and health care-associated infections overall cost the nation $30 billion annually. He called carbapenem-resistant Enterobacteriaceae infection a particularly serious threat, and noted that everything from cancer chemotherapy to organ transplants to complex surgeries will not be possible if "we don't take action."

Frieden praised hospitals that have implemented antibiotic stewardship programs, and called on all others to do the same. "Unless we improve the stewardship of existing antibiotics, developing new ones won't solve the problem," he said.

He asked hospital leaders to participate in the CDC's antibiotic-resistance initiative, which aims to facilitate efforts in every state, accelerate the detection of outbreaks, encourage innovations on prevention and improve antibiotic use.

Frieden pointed to last year's Ebola crisis as an example of how hospitals, working with the CDC, stepped up to confront a major health care threat. The nation's health care system is much more prepared to identify and treat individuals with Ebola, and that "couldn't have happened without the active participation of hospitals and the AHA," he said, asking for that same commitment to antibiotic stewardship.