“The Covid-19 pandemic demonstrated America’s vulnerability to catastrophic public health crises, and it highlighted the urgency of taking reasonable measures to prevent them in the future,” Senator Todd Young, an Indiana Republican and one of the bill’s co-sponsors, said in an email. “The next public health crisis is already here: the emergence of bacteria resistant to antibiotic treatment.”

In a letter to Congress in November, opponents of the measure said it would encourage the development of ineffective drugs, in part because of what they describe as flaws in the F.D.A.’s existing approval process for antibiotics. “Under the Pasteur Act, taxpayer dollars will be wasted as a blank check to pharmaceutical manufacturers for antimicrobials of limited benefit,” they wrote.

One of the signers, Dr. Reshma Ramachandran, an assistant professor at the Yale School of Medicine, said the bill leaves in place a regulatory regimen for antibiotics that she and others contend allows companies to market drugs of questionable value. Her objection to the status quo centers on a central tenet of the F.D.A.’s antibiotics review process: New drugs can be approved under a concept known as noninferiority, which allows novel medications to be less effective than existing ones. Dr. Ramachandran, whose work focuses on antimicrobial resistance and health policy, and other critics of the bill said that the F.D.A. should adopt a system that requires drugmakers to prove that new antibiotics are superior to current ones.

“As a clinician, it’s a huge concern for me that we could have new costly drugs on the market without regulatory oversight to actually ensure these drugs are clinically meaningful or that they even address resistant infections,” Dr. Ramachandran said.

Many experts, however, say that such an approach is impractical and raises ethical questions. To establish whether a new antibiotic is superior to existing ones, researchers would have to conduct clinical trials that test the new therapy against a placebo or a drug they know to be less effective. For study participants battling an infection, getting a placebo or an inferior drug could prove deadly.

“This whole superiority notion makes no sense. We don’t hold any drug to that standard,” said Kenneth E. Thorpe, a health policy official in the Clinton administration who is an adviser to the advocacy group Partnership to Fight Infectious Disease. “We need to spur innovation and get as many novel antibiotics as we can given the diversity of infections and the threat to human health if we fail.”