Development of a novel murine model for treatment of infected mesh scenarios

Indications regarding hernia repair after removal of previously infected prostheses remain unclear. Patients may receive staged primary repair or single-stage reconstructions, neither of which may be ideal. Although animal models have simulated contamination by direct inoculation of implants with bacteria, there remains a paucity of literature, which simulates a field following mesh infection and removal. We aimed to develop a murine model to mimic this complex scenario to allow for further testing of various implants.

Thirty-six female CL57BL/6J mice underwent implantation of a 0.7 × 0.7 cm polyester mesh in the dorsal subcutaneous position. Wounds were closed and inoculated with 100 µL containing 1 × 10⁴ CFU of GFP-labeled MSSA. After 2 weeks, the infected mesh was removed and the cavity was copiously irrigated with saline. Mice were split into four groups: with three groups receiving new polyester, polypropylene, and porcine mesh and remaining as non-mesh controls. Mice were survived for another 2 weeks and underwent necropsy. Gross infection was evaluated at 2 and 4 weeks. Tissue homogenization and direct plating to recover GFP MSSA was completed at 4 weeks.

At 2 weeks, all mice were noted to have gross mesh infection. One animal died due to overwhelming infection and wound breakdown. At 4 weeks, 5/6 (83 %) control mice who did not have a second mesh implantation had full clearance of their wounds. In contrast, 9/10 (90 %) mice with re-implantation of polypropylene were noted to have pus and recovery of GFP MSSA on plating. This was also observed in 100 % of mice with polyester and porcine mesh.

Our novel murine model demonstrates that mesh re-implantation after infected mesh removal results in infection of the newly placed prosthesis, regardless of the material characteristic or type. This model lays foundation for development and investigation of implants for treatment strategies following infected mesh removal.