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An independent 2004 evaluation of bacterial cultures collected from hands in more than 200 upper-Manhattan households did not find a relationship between resistance to triclosan and resistance to antibiotics. The lead author on that study was Dr. Allison Aiello, now assistant professor of epidemiology at the University of Michigan. She believes that too little research has been done to date, and much of what has been done was funded by industry.
Says Aiello, “There is still a big gap in surveillance and research on the ground.” Now that lab research has made clearer the potential mechanisms by which triclosan might help breed bacteria resistant to clinical antibiotics, she says, “We need rigorous, independent, long-term studies on household use to fill the gaps in our knowledge.”
Brian Sansoni also welcomes more research, but he says it shouldn’t matter who pays for it: “The fact is, it’s industry’s responsibility to undertake and/or fund research on the ingredients they produce or use in their products. It’s a part of good product stewardship.”
Back in the laboratory, there are hints of trouble. Research has shown, for example, that lab-selected strains of the disease-causing bacteria Salmonella enterica and E. coli O157 resistant to triclosan or benzalkonium chloride also showed increased resistance to antibiotic drugs. Such “cross-resistance” has been associated with use of other disinfectants as well, including pine oil, which is the natural active ingredient in Pine-Sol.
Aiello points to another potential worry: “The triclosan concentrations used in medical settings are quite high, and are effective. But my work shows that the concentration in household soaps and detergents [only a tenth to a half of one percent, which is diluted further in cleaning] is too low to be very effective in reducing illness.” On the other hand, she says, that lighter exposure may be just right for leaving behind genetically adapted bacteria.
To Sansoni, the threat of bacterial resistance is “suburban mythology.” Pointing to the research of Aiello and others, he says, “The studies and the research to date have shown there is no real world evidence linking the use of antibacterial products to antibiotic resistance.”
“It is a shame,” he adds, “that a few loud voices are trying to equate use of antibacterial products in the same breath with the known contributor to the antibiotic-resistance problem: the over prescription of antibiotic drugs by the medical community. It’s like trying to compare an anthill to Mount Everest.”
The associate director of the Clinical Microbiology Laboratory at the University of Nebraska Medical Center in Omaha, Dr. Paul Fey, says he would be concerned if, as some studies indicate, the molecular “pumps” that resistant bacteria use to rid themselves of triclosan could also flush out medically important antibiotics. “That’s another good reason why triclosan and other antibiotics should not be used in soaps, plastics, et cetera. And it’s unnecessary. Plain soap itself is one of the best antimicrobials there is.”
Sansoni cites an issue brief his group provided for a US Food and Drug Administration (FDA) advisory committee in 2005, describing the benefits of antimicrobial bars, liquids, gels, and wipes. In the end, that committee issued a nonbinding statement saying that in routine use, antibacterial soaps are no better at fending off illness than is regular soap, and that they might contribute to antibiotic resistance in bacteria. The FDA took no action in response to the panel’s recommendation.
Beyond the kitchen sink
Proctor & Gamble scientists have published studies showing that sewage treatment can break down triclosan. But, says Dr. Rebecca Sutton, staff scientist of the Environmental Working Group, “Our current water-treatment processes are not designed to deal with it, and they aren’t dealing with it.” She points to numerous studies finding triclosan and triclocarban througout the environment, including the waters of San Francisco Bay.
The US Geological Survey reported in 2002 on a wide range of potential pollutants found in streams across the country. Triclosan was identified in 58 percent of the samples. Out of 95 chemicals surveyed, triclosan was one of the most commonly detected, outstripped by only three others: caffeine, cholesterol, and a metabolite of nicotine.