Germ fighters may lead to germ resistance

Germ fighters may lead to hardier germs

By TARA PARKER-POPE Published: October 31, 2007
http://www.iht.com/articles/2007/10/31/hea...sshealthscience


Reports of schoolchildren dying from infections with drug-resistant bacteria are enough to send parents on an antimicrobial cleaning frenzy. But before you start waging your own personal war on single-celled organisms, be warned. Many household and personal cleaners contain ingredients that could make the resistance problem worse. Today, hundreds of soaps, hand lotions, kitchen cleansers and even toothpastes and mouthwashes include antibacterial agents. One of the most popular is triclosan, which has been used not only in cleaners but also to coat toys, cutting boards, mouse pads, wallpaper and even dog bowls. The temptation to blanket our families with antibacterial protection has been fueled by scary news reports about a deadly bacteria called CA-MRSA, which stands for community-acquired methicillin-resistant Staphylococcus aureus. Two otherwise healthy children — a seventh-grader in Brooklyn and a high school football player in Virginia — died in recent weeks from MRSA infections. The general advice for avoiding infection is basic hygiene — washing hands or using alcohol-based sanitizers, keeping scrapes covered until healed and refraining from sharing personal items like towels and cosmetics. But some recent laboratory studies suggest that antibacterial products containing triclosan may not be the best way to stay clean. Instead of wiping out bacteria randomly, the way regular soap or alcohol-based products do, triclosan may inhibit the growth of bacteria in a way that leaves a larger proportion of resistant bacteria behind, according to lab studies at Tufts University and Colorado State University, among others. In fairness, none of the research has shown this effect in the real world. In fact, two randomized studies comparing people who used triclosan hand soaps with people who used plain soaps found no evidence that triclosan contributed to bacteria resistance. The soap industry says these results are far more compelling than the controlled lab studies. But Allison E. Aiello, an assistant professor of epidemiology at the University of Michigan School of Public Health, says the laboratory evidence against triclosan is compelling enough to raise questions about the products. More meaningful, she says, is that several studies show that antibacterial soaps sold to consumers are no better than plain soaps in terms of reducing illness or the count of bacteria left on hands. "Given that there doesn't seem to be a benefit, I think it warrants further evaluation," said Aiello, whose review article on antibacterial soaps was published last month in the medical journal Clinical Infectious Diseases. "We should be questioning use of these products." Soap companies say the worry about triclosan takes the focus away from the real culprit: the abuse of antibiotics and the need for better hygiene in general. "The last thing we want to see is people discouraged form using beneficial hygiene products," said Brian Sansoni, a spokesman for the Soap and Detergent Association. In any given colony of bacteria, some portion will often have a natural resistance to antibiotics. The resistant germs might contain genetic variants that give them stronger cell walls, or pumps that allow them to spit the antibiotic back out. They survive the antibiotic onslaught, and with the susceptible bacteria out of the way, naturally resistant strains can thrive. Not only do they multiply, but some can also share their resistance with other bacteria and collect new resistance traits over time. Natural resistance happens on such a small scale that it is generally not a health worry. But when antibiotics are overused — either by individuals or when farmers add them to animal feed — the effect is amplified. "You're going to have this exaggerated, snowballing effect of resistant bacteria multiplying all around you," said Marlene Zuk, a biology professor at the University of California, Riverside, whose book "Riddled With Life" discusses the proliferation of antibacterial cleaners and personal products. The question about cleaners containing triclosan is whether the agent kills germs randomly or whether it promotes the same selection pressures that can lead to antibiotic resistance. The worry is not that bacteria might become resistant to triclosan. The fear is that the same bacteria that resist triclosan can also resist certain antibiotics. And a handful of lab studies have suggested that triclosan may select for resistant bacteria. "Here you have a substance that has been widely used in hospital settings and household settings," said Herbert P. Schweizer, associate director for research at the department of microbiology, immunology and pathology at Colorado State, who conducted some of the lab studies showing triclosan resistance. "The exposure to this widely used antimicrobial caused emergence of multidrug resistance in laboratory strains." That studies of triclosan use haven't shown a resistance problem in the community doesn't mean it won't happen, said Dr. Stuart B. Levy, a microbiology professor at Tufts who is president of the Alliance for Prudent Use of Antibiotics. "I'm the first to say we haven't seen a difference yet in the home," Levy said. "We know from antibiotic data that if it happens in a lab it will eventually happen outside the lab."