Silver carboxylate and titanium dioxide-polydimethylsiloxane coating decreases adherence of multi-drug resistant Serratia marcescens on spinal implant materials.

The opportunistic multi-drug resistant nosocomial gram negative bacilli Serratia marcescens (S. marcescens) is a rising contributor to spinal implant infections (Iguchi et al., Genome Biol Evol 6:2096–2110, 2014; Teresa et al., J Clin Microbiol 55:2334–2347; Dante et al., J Clin Microbiol 54:120–126). This study investigates the most effective matrix ratio of an antibiotic-independent, silver carboxylate-doped titanium dioxide (TiO2)-polydimethylsiloxane (PDMS) coating in preventing adherence of multidrug resistant pathogen S. marcescens to spinal implant materials. This project examined an antibiotic-independent, silver carboxylate-doped titanium dioxide (TiO2)-polydimethylsiloxane (PDMS) coating on three common spinal implant materials, polyetheretherketone (PEEK), stainless steel (SS), and titanium (Ti), which previously were found to be prone to bacterial adhesion (Garcia et al., Spine Deform 8:351–359). After generation of dose response curves to find the optimal silver carboxylate concentration, 95% TiO2-5% PDMS was combined with 10× silver carboxylate and compared to 100% silver carboxylate and uncoated implants. Implants were imaged using scanning electron microscopy and confocal laser scanning microscopy to detect adherent S. marcescens. Ninety-five percent TiO2-5% PDMS and 10× silver carboxylate coating decreased adherence of S. marcescens on PEEK by 99.61% (p = 0.001), on titanium by 98.77% (p = 0.001), and on stainless steel by 88.10% (p = 0.001) after 24 h. The average decrease in bacterial adherence was 95.49% compared to uncoated implants. A coating composition comprised of 95% TiO2-5% PDMS matrix and 10× silver carboxylate most effectively decreases adherence of S. marcescens on spinal implants. These results suggest that the application of a non-antibiotic, bactericidal coating prior to spinal surgery may prevent the adherence and proliferation of MDR S. marcescens and decrease the incidence of spinal SSI.