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Repeated Exposure to Triclosan Reduces Virulence in S. aureus
Repeated laboratory exposures to triclosan reduced susceptibility to antibiotics in Staphylococcus aureus, but probably not sufficiently to render commonly used antibiotics ineffective, according to a paper in the June 2012 issue of the journal Antimicrobial Agents and Chemotherapy. It also generated less virulent, less fit "small colony variants" of the pathogen.
The research is important, because concern has arisen that antiseptics and disinfectants might cause bacteria to develop reduced susceptibility to these compounds, as well as to antibiotics, to the point where for some uses, in some countries, they have been strictly regulated, says principal investigator Andrew McBain, of the University of Manchester, UK. S. aureus is an important source of hospital- and community-acquired infections. Triclosan is a broad-spectrum antibacterial and antifungal compound often used in cleaning supplies, personal care products, toys, and other consumer products, as well as in clinical settings, for example, to reduce methicillin-resistant S. aureus infections.
The research began serendipitously when, during an unrelated study, Sarah Forbes, a PhD student in McBain's lab, created a population of small colony variants by serially exposing S. aureus ten times on concentration gradients of triclosan. "This type of selection system we used represents a worst case scenario in terms of altering bacterial susceptibility because of the repeated and continuously elevating high level exposure," says McBain. "We then grew this strain a further ten times on triclosan-free medium to see if it could recover." The exposed strain had reduced susceptibility to triclosan, and it was def
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American Society for Microbiology