Ayear and a half ago, researchers found that a deadly form of staph infection was prevalent on Canadian pig farms. This year, the superbug was found in both swine and workers at U.S. farms.

The rise of bacteria such as methicillin-resistant Staphylococcus aureus, or MRSA, which kills more people in this country each year than AIDS, is believed to be a consequence of the overuse of antibiotics in humans and animals. Low doses of the medications have become ubiquitous in the livestock industry, mixed into feed to enhance growth and prevent the diseases that sweep through crowded pens.

A panel of experts found “clear evidence of adverse human health consequences due to resistant organisms resulting from nonhuman usage of antimicrobials,” the World Health Organization reported in 2004. “These consequences include infections that would not have otherwise occurred, increased frequency of treatment failures (in some cases death) and increased severity of infections.”

The European Union has already banned non-therapeutic use of antibiotics in farm animals, but each year lobbying by agribusiness in this country dooms legislation that would do the same. On Tuesday, Rep. Louise M. Slaughter (D-N.Y.) introduced a bill that would restrict the use of antibiotics that are important to human health in farming operations. The medications could be used to treat illness, but not as a growth promoter or as a substitute for cleaner living conditions. The bill might have a better chance of passing now, with a stronger Democratic majority in Congress.

The timing is right in other ways as well. In January, the Department of Agriculture -- responsible for promoting the meat industry as well as consumer health -- reported that, except during the nursery stage for young pigs, the costs of using preventive or growth-promoting antibiotics slightly outweighed the economic benefits for farms. That’s not counting the added costs to consumers in prescription prices for more exotic antibiotics or the $4 billion a year this country spends to combat resistant infections. Some farms are successfully using better sanitation and tracking of illnesses among their herds instead of preventive antibiotics.

It would be a mistake to delay restrictions on antibiotic use until the situation has a chance to reach dire proportions; there is no guarantee that specialized antibiotics could be developed in time to thwart a new wave of drug-resistant bacteria. Humans don’t need antibiotics to treat common colds, which are caused by viruses rather than bacteria, and animals don’t need them to grow.