Article
Bacterial adhesion characteristics and biofilm formation on implant materials for intervertebral cages
Adhäsionscharakteristika von Bakterien und Biofilmbildung auf verschiedenen Implantatmaterialen für intervertebrale Cages
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Published: | June 26, 2020 |
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Objective: Infections of the spine are a rare but increasing pathology. Surgical intervention with intercorporal stabilization is increasingly recommended. However, there is no guideline which material for intervertebral cages should be used. The aim of this study was to compare titanium and PEEK cages according to their adhesion characteristics of different bacteria in vitro.
Methods: Platelets made from PEEK, polished titanium (Ti) and polished/porous structured titanium (TiMe) as well as original PEEK and porous trabecular structured titanium (TiLi) cages were inoculated with S.aureus (MSSA, MRSA), S.epidermidis and E.coli. Growth characteristics of serial dilutions of bacteria suspensions after sonication were analysed. Biofilms and bacteria were visualized under a confocal laser scanning and a crossbeam electron microscope.
Results: Platelets: Platelets showed significant differences between PEEK/Ti (p=0.04) and Ti/TiMe (p=0.004) after 80h for S.epidermidis with 67.7 vs. 7.0 and 7.0 vs. 40.3 colony-forming units (CFU). In MSSA significant differences were seen for PEEK/TiMe after 32h with 1.3 vs. 22.7 CFU (p=0.006). After 80h additional growth differences were found for PEEK/Ti (118.7 vs. 37.0 CFU; p=0.03), PEEK/TiMe (118.7 vs. 49.7 CFU; p=0.04). In MRSA significant differences could be detected for PEEK/TiMe (1.0 vs. 6.3 CFU; p=0.02) at 56h and PEEK/TiMe (40.3 vs. 6.3 CFU; p=0.009) at 72h as well as PEEK/Ti (83.3 vs. 33.3 CFU; p=0.007) and Ti/TiMe (33.3 vs. 96.7 CFU; p=0.003) at 80h.
Cages: For PEEK and TiLi cages significant differences were found at 72h for S.epidermidis (2913 vs. 230 CFU; p<0.001), E.coli (398 vs. 836 CFU; p<0.001) and MRSA (14.9 vs. 8.3 CFU; p<0.001). For MSSA a significant difference could be seen at both time points (8 and 72h; p<0.001) with 1.4 vs. 0.22 and 2.6 vs. 0.9 CFU. Electron microscopy demonstrated enhanced adhesion in transition areas of material structure. No increased adhesion could be shown in porous compared to polished areas.
Conclusion: For S.epidermidis MSSA and MRSA PEEK cages showed a significantly higher count of CFU, whereas for E.coli PEEK seemed to be advantageous over titanium. Interestingly, electron microscopic visualization could show that bacteria did not adhere at the titanium mesh structure, but at the border zones of polished material to rougher parts.