Inhibitory efficacy of geraniol on biofilm formation and development of adaptive resistance in Staphylococcus epidermidis RP62A

Purpose. The current study has been designed to delineate the efficacy of geraniol (GE) on biofilm formation in Staphylococcus epidermidis as well as the effect of subinhibitory concentrations of GE on the development of adaptive resistance. Methodology. Biofilm biomass quantification assay was performed to evaluate the antibiofilm activity of GE against S. epidermidis. Microscopic observation of biofilms and extracellular polymeric substance (EPS), slime and cell surface hydrophobicity (CSH) production were also studied to support the antibiofilm potential of GE. In addition, S. epidermidis was examined for its adaptive resistance development upon continuous exposure of GE at its subinhibitory concentrations. Results/ Key findings. The MIC of GE against S. epidermidis was 512 mu g ml(-1). Without hampering the growth of the pathogen, GE at its sub-MICs (50, 100, 150 and 200 mu g ml(-1)) exhibited a dose-dependent increase in antibiofilm activity. The minimal biofilm inhibitory concentration (MBIC) of GE was found to be 200 mu g ml(-1) with a maximum biofilm inhibition of 85 %. Disintegrated biofilm architecture, reduced EPS, slime and CSH production validated the antibiofilm efficacy of GE. Although the action of GE on preformed biofilm is limited, a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay and live/dead cell staining method revealed reduction in the viability (47 %) of biofilm inhabitants at 2 x MIC concentration. Sequential exposure of S. epidermidis to the sub-MICs of GE resulted in poor development of adaptive resistance with diminished biofilm formation. Conclusion. The present study highlights the potential of GE as a suitable candidate for the control of biofilm-mediated S. epidermidis infections.