VIRULENT MICROBES, such as Escherichia coli O157, are emerging at a frightening rate. And many disease organisms are becoming resistant to modern antibiotics.

Some researchers warn that the antimicrobial ingredients in soaps and other household products could contribute to the problem.

Killing bacteria is like hitting a moving target--just when you think you've got them, they mutate on you. Through the overuse and misuse of antibiotics, doctors and farmers have unwittingly spawned or accelerated the development of strains of bacteria that survive conventional antibiotic attack. To keep drugs potent, many in the medical community preach judicious use of antibiotics and teach patients to take their full course of medication. But just when the tide may be turning in the medical world, new battle lines are forming in unlikely places--America's kitchens and bathrooms.

The marketing of antimicrobial soaps, hand lotions, sponges and kitchen surfaces has increased in recent years. These novel products contain bacteria-busting compounds such as zinc pyrithione, hydrogen peroxide or, most commonly in soaps, triclosan.

But such germ killers could perversely lead to more harmful strains in the home, according to Stuart B. Levy, a medical researcher at Tufts University. Levy decried the growing casual use of these products at "Modern Plagues: Emerging and Re-Emerging Infectious Diseases," a symposium sponsored by the Whitehead Institute for Biomedical Research and the Massachusetts General Hospital this past May. "Antibiotics are societal drugs," said Levy, author of The Antibiotic Paradox: How Miracle Drugs are Destroying the Miracle (Plenum Press, 1992). "Any use affects what's out there."

Resistant strains of bacteria generally emerge through evolutionary selection: in any situation where antibiotics are used, cells that can survive exposure to the drugs gradually replace their more vulnerable cousins. Hospitals, where both antibiotics and germs are abundant, have long been recognized as unintentional breeding grounds for resistant bacteria. Two hospitals in the same city may be confronted with two different sets of resistance problems, depending on individual patient populations and the way antibiotics are used.

Domestic antibacterials are distinct from medical antibiotics, but they may pose a parallel danger. Levy cautions that just as every hospital develops its own antibiotic-resistance profile, resistance within an individual home's microbial ecology could be altered by the misuse of home antibacterial products. The risk runs from hardier E. coli to tougher Streptococcus pyogenes and pneumococci. "I'm not saying it's a problem," he noted. "It's a potential problem."

WINNING THE RACE? The Harvard Medical School's Mary E. Wilson, predicts that infectious disease "will be with us for the foreseeable future."

To prevent the potential from becoming a reality, Levy urges that people not use such products regularly. Rather, they should save the antibacterials for critical situations, such as when a patient returns from the hospital. Then, the sudden appearance of the bacteria-fighting agents can indeed wreak havoc on a local microbial population that is not yet used to dealing with them. But manufacturers usually tout their antibacterial soaps and lotions as suitable for everyday use.

A recent surge in the attention paid to the issue of antibiotic resistance attests to the medical community's recognition that the heady days of easy antibiotic and vaccine victories are over. In 1969, U.S. Surgeon General William Stewart testified before Congress that we could "close the book on infectious disease." The hard-won wisdom of 1997 was summed up by another symposium participant, the Harvard Medical School's Mary E. Wilson, who has closed the book on Stewart's hubris. "Infectious disease," she pronounced, "will be with us for the foreseeable future."