Lack of Evidence for Reduced Fitness of Clinical Staphylococcus aureus Isolates with Reduced Susceptibility to Triclosan

Decreased susceptibility to biocides in bacteria has raised increased levels of attention in recent years due to a claimed hazard related to potential selection for antibiotic-resistant strains. In this context, Latimer et al. characterized Staphylococcus aureus ATCC 6538 mutants selected by the biocide triclosan for their in vitro phenotypes and virulence potential (3). Phenotypic characterization was carried out on one mutant (P10) that had been passaged 10 times in a triclosan gradient. Mutant P10 exhibited multiple phenotypes, including small colony size, slow planktonic growth, impaired biofilm formation, impaired hemolytic activity, impaired coagulase activity, and impaired virulence, in a model of Galleria mellonella infection. From the analysis of the P10 mutant, it was concluded that triclosan may select for reduced susceptibility to triclosan but that this reduced susceptibility may be associated with deficiencies in growth and virulence (3).