Common Biocide Promotes Bacteria in Nasal Passages

Triclosan, an antimicrobial agent found in common household soaps, shampoos, and toothpastes promotes the colonization of Staphylococcus aureus in noses, according to a new study.

Researchers at the University of Michigan (Ann Arbor, USA) conducted a study that examined the nasal passages of healthy adults, which found that 41% of those sampled had traces of triclosan in their nasal secretions; the presence of triclosan in the secretions also trended positively with nasal colonization by S. aureus. Additional experiments found that S. aureus grown in the presence of triclosan was better able to attach to human proteins, and that rats exposed to triclosan were more susceptible to S. aureus nasal colonization.

The researchers also demonstrated that triclosan could promote the binding of S. aureus to host proteins such as collagen, fibronectin, and keratin, as well as inanimate surfaces such as plastic and glass. According to the researchers, the data contributes to the growing body of research that demonstrates the unintended consequences of unregulated triclosan, as well as the inadvertent effects of triclosan on the environment and human health, since it also decreases circulating levels of thyroxine hormone (T4), which could lead to altered behavior, learning disabilities, and infertility. The study was published on April 8, 2014, in mBio.

“Triclosan has been around for the past 40 years. It's really common in hand soaps, toothpastes, and mouthwashes but there's no evidence it does a better job than regular soap,” said senior author Blaise Boles, PhD, an assistant professor of molecular, cellular and developmental biology. “This agent may have unintended consequences in our bodies. It could promote S. aureus nasal colonization, putting some people at increased risk for infection.”

Triclosan is a polychlorophenoxyphenol antibacterial and antifungal agent that has been shown to be effective in reducing and controlling bacterial contamination on the hands and on treated products. In use since 1972, triclosan is also found in health care settings, such as in surgical scrubs and personnel hand washes. More recently, showering or bathing with 2% triclosan has become a recommended regimen in surgical units for the decolonization of patients whose skin carries methicillin-resistant Staphylococcus aureus (MRSA).

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