Abstract
Aim
The aim of this study was to establish an implant-associated osteomyelitis model in rats with the ability to quantify biofilm formation on implants for prospective evaluation of antibacterial effects on micro-structured implant surfaces.
Method
Staphylococcus aureus (strain 36/07) suspension with infection concentrations of 106, 105, 104 and 103 CFU/10µl, respectively was injected in the tibia of 32 rats (n=8 per group). Afterwards a titanium implant (0.8×0.8×12 mm) was inserted. 8 rats were implanted with a preincubated implant (107 CFU/ml, 12 h) and 8 rats served as a control (injection of 0.9% NaCl). During the follow up, clinical, radiographic and µ-CT examinations were conducted. On day 21 post op, all rats were sacrificed. Implant and tibia were explanted under sterile conditions. The implant was stained with green and red fluorescent nucleic acid dye (live/ dead) and analyzed by confocal microscopy. The amount of vivid and dead biomass as well as vivid bacteria on the implant surface was calculated with an image software*.
Results
In all groups with artificial infection, local bacterial colonization could be detected without systemic infection. While clinical signs of infections (lameness, subcutaneous abscesses) decreased, the volume of bacterial colonization increased on the implant surface with decreasing initial infection CFU. Preincubated implants showed a similar bacterial colonialization of the surface as implants which were infected with 106 CFU as well as a similar bone disintegration due to ongoing osteomyelitis.
Conclusions
Establishment of the implant-associated infection model in rats with subsequent quantification of the vivid bacterial volume via confocal microscopy was successful and is now applicable for the evaluation of micro-structured antibacterial implant surfaces. Pre incubation of implants with initiating biofilm formation was established as alternative onset of infection.
This work was part of BIOFABRICATION for NIFE and funded by Volkswagen Foundation and MWK.
* Imaris® ×64 6.2.1
