Playing It Smart in the War Against Disease-Causing Bacteria

National Wildlife, Feb-March, 1999

Antibacterial." The word is suddenly all over the place--on soaps, household cleaners, toothbrushes, lotions, toys and even socks. It's enough to make you think germs are waging war on us. And you would be right. Disease-causing bacteria have become both more virulent and more mobile than ever before.

But before you use those new antibacterial products, consider: When they work, they may contribute to the problem, and the claims for their effectiveness are not always all they are cracked up to be. "I'm not sure they are doing anything except hyping the product," says microbiologist Stuart Levy, head of the Center for Adaptation Genetics and Drug Resistance at Tufts University School of Medicine. "It's playing on the misinterpretation by the public that bacteria are all bad, that bacteria are out to get you."

Welcome to the paradoxes of the antibiotic age. For five decades--ever since penicillin became widely available in the 1940s--antibiotics have been miracle drugs, successfully fighting most diseases caused by the tiny, single-celled organisms. But all that time bacteria have been fighting back, with strategies that dazzle and terrify scientists. And public misunderstandings of the threats, the science and the best ways to stay healthy have been a big part of the problem.

Microbiologists recently estimated that the world holds five million trillion trillion (a five followed by 30 zeros) bacteria--the most ubiquitous wildlife on the planet. At around a millionth of a meter in diameter, they don't need circulatory systems. Nutrients simply diffuse. With no blood vessels or bones to get tangled up, bacteria can have limbs that rotate, pulling or pushing them along like propellers. They also can fasten themselves to surfaces. And they easily hitch rides on international flights from one side of the world to the other in hours.

The habitats of various strains range from hot-water vents on the ocean floor to the polar ice caps. "Bacteria have the ability to withstand tremendous environmental extremes," says Hans Paerl, a University of North Carolina ecologist who studies Antarctic bacteria. "There are clearly advantages to being simple and small."

The microbes are on our skin, in our mouths and on everything we touch-- and most pose no risk to humans. Some, on the other hand, can be dangerous and even deadly. Chances are a scientist could culture disease-causing bacteria such as Staphylococcus aureus from your skin. If you cut yourself, you could get infected. That's why doctors advise washing wounds and keeping them as clean as possible--and that's also why your immune response is a critical defense.

The facts that bacteria are everywhere and most are harmless to us are at the heart of the potential problems with antibacterial products. When the products are effective, they attack bacteria indiscriminately, which likely opens up niches for other, perhaps more dangerous bacteria to come calling. "We aren't going to sterilize our world," says Levy. And trying to do so could make the very bacteria we want to eliminate stronger than ever. That's what has happened with antibiotic drugs that are taken internally, most of which work by interfering with biological processes of bacteria. Penicillin, for example, interferes with cell- wall construction. But as the organisms multiply, some mutations invariably develop, and when one bacterium develops resistance to a drug, it can thrive under conditions that kill others.

The ways the organisms thwart drugs give new meaning to the term "germ warfare." Some essentially eject the drugs from their bodies, some make enzymes that render the drugs ineffective and some change the molecular targets that antibiotics latch onto. Survivors not only pass on their abilities to their offspring, they trade resistance genes with other bacteria.

So in the last few decades we've seen whole new pathogens and fiercer versions of old favorites. A disease-causing strain of E. coli that sickened almost 10,000 people in Japan in 1996, for example, was not known to cause illness until 1982 and may not have existed before the 1940s. Drug-resistant staph infections have become serious problems in hospitals. In 1997, a few rare strains of staph around the world began to resist even antibiotic heavyweight vancomycin.

Researchers used to think that the antibacterial agents in household products fell into the category of unsubtle weapons of mass destruction. (That category includes hydrogen peroxide and bleach, which kill primarily through drying and oxidation. Think napalm.) But last summer, a paper in the journal Nature by Levy and colleagues reported that the ingredient triclosan, often used in the new household products, is more subtle. Triclosan kills bacteria by preventing them from making fatty molecules that are part of their cell membranes.

That's the sort of targeted attack that bacterial mutations often can overcome. So the more we use triclosan--and possibly other antibacterial agents as well--the greater the chance of encouraging the growth of strains that can resist the chemicals, concludes Levy. For their part, manufacturers suggest that such discoveries could lead to more powerful agents in the future, and they maintain that their products serve a vital public health role when used appropriately. Indeed, hospitals have long used antibacterial cleaners similar to the household versions.