Actions of Farnesol and Xylitol against <i>Staphylococcus aureus</i>

Abstract

<i>Background:</i> Heavy colonization of atopic dermatitis (AD) with <i>Staphylococcus aureus</i> is well documented. The isolation rate of methicillin-resistant <i>S. aureus</i> is high in strains from AD in Japan. Our objective in the present study was to investigate the actions of farnesol and xylitol against <i>S. aureus</i> for the control of AD skin lesion-colonizing <i>S. aureus.</i><i>Methods:</i> We examined the actions of farnesol on plasma coagulation and superantigenic exotoxin production by <i>S. aureus,</i> the antimicrobial activity of β-lactam antibiotics combined with farnesol at concentrations below the minimal inhibitory concentration (MIC) and the effect of xylitol on glycocalyx production. <i>Results:</i> Coagulation by <i>S. aureus</i> cells was inhibited in plasma containing farnesol at a concentration of 1/12 of the MIC (100 µg/ml) after incubation for 24 h. The production of superantigenic exotoxins by <i>S. aureus</i> cells with farnesol (100 µg/ml) was about 10 times lower than that by <i>S. aureus</i> cells alone. The MICs of ampicillin and cefdinir against <i>S. aureus </i>were reduced to ≤0.06 µg/ml in Mueller-Hinton agar plates with farnesol (100 µg/ml). We suggest that farnesol at concentrations above the MIC had a suppressive effect against <i>S. aureus </i>cells in the exponential and stationary phase and acted on the cell wall of <i>S. aureus</i> cells in both phases. <i>Conclusions:</i> Farnesol is a promising adjuvant agent against <i>S. aureus</i> skin infections treated with β-lactam antibiotics. Further, 5% xylitol inhibited glycocalyx production by <i>S. aureus</i> cells and consequently had a suppressive effect on the colonization of <i>S. aureus </i>on the horny cells of AD lesions.