The biocide triclosan induces (p)ppGpp dependent antibiotic tolerance and alters SarA dependent biofilm structures inStaphylococcus aureus

Abstract

AbstractThe biocide triclosan is used extensively in both household and hospital settings. The chronic exposure to the biocide occurring in individuals that use triclosan-containing products results in low levels of triclosan present in the human body that has been linked to induction of antibiotic tolerance and altered biofilm formation. Here we aimed to unravel the molecular mechanisms involved in triclosan induced antibiotic tolerance and biofilm formation inStaphylococcus aureus. Triclosan treatment prior to planktonic exposure to bactericidal antibiotics resulted in 1,000 fold higher viable cell counts compared to non-pretreated cultures. Triclosan pretreatment also protectedS. aureusbiofilms against otherwise lethal doses of antibiotics as shown by live/dead cell staining and viable cell counting. Triclosan mediated antibiotic tolerance in planktonic and biofilm cultures required an active stringent response because a pppGpp0strain was not protected from antibiotic killing. Incubation ofS. aureuswith triclosan also altered biofilm structure due to SarA-mediated overproduction of the polysaccharide intercellular adhesin (PIA) in the biofilm matrix. Thus, physiologically relevant concentrations of triclosan can trigger (p)ppGpp dependent antibiotic tolerance as well as SarA dependent biofilm formation.ImportanceThe prevalent bacteriumStaphylococcus aureusinfects skin lesions and indwelling devices, and this can cause sepsis with 33% mortality. Intrinsic to this is the formation of co-ordinated communities (biofilms) protected by a polysaccharide coat.S. aureusis increasingly difficult to eradicate due to its antibiotic resistance. Protection against Methicillin ResistantS. aureus(MRSA) includes pre-hospital admission washing with products containing biocides. The biocide triclosan is the predominant antibacterial compound in sewage in Ontario due to its use in household and hospital settings. Levels of triclosan accumulate with exposure in humans. The significance of our research is in identifying the mechanisms triggered by exposure ofS. aureusto physiological levels of triclosan that go on to raise the tolerance ofS. aureusto antibiotics and promote the formation of biofilms. This understanding will inform future criteria used to determine effective antimicrobial treatments.