Triclosan promotes Staphylococcus aureus nasal colonization

Abstract

The biocide triclosan is used in many personal care products, including toothpastes, soaps, clothing, and medical equipment. Consequently, it is present as a contaminant in the environment and has been detected in some human fluids, including serum, urine, and milk. Staphylococcus aureus is an opportunistic pathogen that colonizes the noses and throats of approximately 30% of the population. Colonization with S. aureus is known to be a risk factor for several types of infection. Here we demonstrate that triclosan is commonly found in the nasal secretions of healthy adults and the presence of triclosan trends positively with nasal colonization by S. aureus. We demonstrate that triclosan can 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. Lastly, triclosan-exposed rats are more susceptible to nasal colonization with S. aureus. These data reveal a novel factor that influences the ability of S. aureus to bind surfaces and alters S. aureus nasal colonization. IMPORTANCE Triclosan has been used as a biocide for over 40 years, but the broader effects that it has on the human microbiome have not been investigated. We demonstrate that triclosan is present in nasal secretions of a large portion of a test population and its presence correlates with Staphylococcus aureus nasal colonization. Triclosan also promotes the binding of S. aureus to human proteins and increases the susceptibility of rats to nasal colonization by S. aureus. These findings are significant because S. aureus colonization is a known risk factor for the development of several types of infections. Our data demonstrate the unintended consequences of unregulated triclosan use and contribute to the growing body of research demonstrating inadvertent effects of triclosan on the environment and human health.

FIG 1

Triclosan influences interactions with the human nares. (A) Nasal secretions were collected from 90 healthy individuals, and an ELISA was performed to determine the concentration of triclosan in each secretion. (B) The same individuals were also swabbed for the presence of S. aureus colonization of the nares. The differences in S. aureus nasal colonization between ≤175 nM triclosan and >175 nM triclosan is statistically significant by ANOVA (P < 0.01). (C) Attachment assays were performed with human serum, collagen, fibronectin (Fnb), and keratin, which are found in nasal secretions, as well as with plastic and glass surfaces. S. aureus treated with 50 nM triclosan bound all of these host proteins and artificial surfaces to a greater extent than untreated cells did (P < 0.05 by t test).

FIG 2

Triclosan-gavaged rats are more susceptible to S. aureus nasal colonization. Cotton rats were gavaged with triclosan or an oil control for 3 days. On day 5, they were challenged with either a small inoculum (10⁵ CFU) or a large inoculum (10⁸ CFU) of S. aureus. On day 12, their noses were removed and S. aureus bacteria were enumerated. Rats gavaged with triclosan were unable to clear the small inoculum, whereas the oil-gavaged rats were able to clear the bacteria from their noses. *, P < 0.01 by t test.