Inhibition of efflux pump encoding genes and biofilm formation by sub-lethal photodynamic therapy in methicillin susceptible and resistant Staphylococcus aureus

•Toluidine blue O-mediated photodynamic therapy could inactivate Staphylococcus aureus.•Sub-lethal photodynamic therapy could inhibit efflux pump functions and impede biofilm formation.•Alterations in efflux pump encoding genes may be one possible mechanism for biofilm formation inhibition.