Background
Infection remains a dreaded complication after implantation of surgical prosthetics, particularly after hernia repair with synthetic mesh. We previously demonstrated the ability of a newly developed polymer to provide controlled release of an antibiotic in a linear fashion over 45 days. We subsequently showed that coating mesh with the drug-releasing polymer prevented a Staphylococcus aureus (SA) infection in vivo. In order to broaden the applicability of this technology, the polymer was synthesized as isolated “microspheres” and loaded with vancomycin (VM) before conducting a non-inferiority analysis.
Materials and Methods
Seventy-three mice underwent creation of a dorsal subcutaneous pocket that was inoculated with 104 CFU of green fluorescent protein (GFP)-labeled SA (105 CFU/ml). Multifilament polyester mesh (7*7mm) was placed into the pocket and the skin was closed. Mesh was either placed alone (n=16), coated with VM-loaded polymer (n=20), placed next to VM-loaded microspheres (n=20) or unloaded microspheres (n=10), or flushed with VM solution (n=7). Quantitative tissue/mesh cultures were performed at 2 and 4-weeks. Mice with open wounds and explanted mesh were excluded.
Results
Twenty-two of twenty-three (96%) tissue-mesh samples from mesh alone or empty miscrospheres were positive for GFP-labeled SA at two and four-weeks. Six of seven (86%) samples from the VM flush group were positive for GFP SA at 4 weeks. Thirty-eight of thirty-eight (100%) VM-loaded pCD-coated mesh or VM-loaded microspheres were negative for GFP SA at two and four weeks.
Conclusion
Slow affinity based drug-releasing polymers in the form of microspheres are able to adequately clear a bacterial burden of SA and prevent mesh infection.