The government is on track to approve a new antibiotic to treat a pneumonia-like disease in cattle, despite warnings from health groups and a majority of the agency’s own expert advisers that the decision will be dangerous — for people.

The drug, called cefquinome, belongs to a class of highly potent antibiotics that are among medicine’s last defense against several serious human infections. No drug from that class has ever been approved in America for use in animals.

The American Medical Association and about a dozen other health groups warned the Food and Drug Administration that giving cefquinome to animals would probably speed the emergence of microbes resistant to that important class of antibiotic, as has happened with other drugs. Those super-microbes could then spread to people.

Echoing those concerns, the FDA’s advisory board last fall voted to reject the request by InterVet Inc. of Millsboro, Del., to market the drug for cattle.

Yet by all indications, the FDA will approve cefquinome this spring. That outcome is all but required, officials said, by a recently implemented “guidance document” that codifies how to weigh threats to human health posed by proposed new animal drugs.

Microbes are constantly mutating, and some of those mutations happen to confer immunity to one drug or another. Exacerbating the problem, bacteria constantly exchange bits of DNA with each other, spreading that resistance.