Fluid Flow and Sub-Bactericidal Release of Silver from Organic Nanocomposite Coatings Enhance ica Operon Expression in Staphylococcus epidermidis

The present study investigates the effect of a silver (Ag)-containing nanocomposite coating on Staphylococcus epider-midis adhesion and icaA gene expression. Bacterial interactions with organic coatings with and without Ag nanoclusters were assessed through a combination of both conventional phenotypic analysis, using microscopy, and genotypic analy-sis, using the relative reverse transcription Real-Time Polymerase Chain Reaction (RT-PCR). The results suggest that the incorporation of Ag in organic coatings can significantly decrease bacterial adhesion and viability with time, in comparison to the organic coating alone. The initial Ag release though at concentrations lower than the bactericidal, significantly increased icaA gene expression for the bacteria interacting with the Ag containing coating two hours post adhesion, especially under the higher shear rate. Stress-inducing conditions such as sub-bactericidal concentrations of Ag and high shear rate can therefore increase icaA expression, indicating that analysis of gene expression can not only refine our knowledge of bacterial-material interactions, but also yield novel biomarkers for potential use in assessing biomaterials antimicrobial performance.