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 Food and Drug Administration's scientific 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 been approved in the United States for use in animals.

The American Medical Association and about a dozen other health groups warned the FDA that giving cefquinome to animals would probably speed the emergence of microbes resistant to that 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.

But the FDA is expected to 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.

Industry representatives say they trust Guidance 152's calculation that cefquinome should be approved. But others say Guidance 152 makes it too difficult for the FDA to say no to some drugs because it requires that the agency show a direct link to human mortality