• Kota Watanabe, Satoshi Fukuzaki, Atsushi Sugino, Nicholas Benson, Newt Metcalf, Masaya Nakamura, and Morio Matsumoto.
• Department of Orthopaedic Surgery, Keio University School of Medicine, Tokyo, Japan.
• Spine. 2021 Sep 1; 46 (17): E911E915E911-E915.

Study DesignIn vitro and in vivo laboratory studies.ObjectiveThis study aimed to compare bacterial survival on titanium alloy (Ti) and cobalt-chromium alloy (CC) using in vitro and in vivo experiments.Summary Of Background DataSpinal implants are frequently manufactured from Ti and CC. These foreign materials are thought to be susceptible to biofilm formation that contributes to the development of surgical site infections. Certain metals (i.e., silver, cobalt) are known to have antibacterial properties.MethodsIn the in vitro study, discs made of Ti or CC were incubated with one of two common bacteria: Staphylococcus aureus (S. aureus) and Propionibacterium acnes (P. acnes). After incubation, discs were assessed to determine the number of viable bacterial cells. In the in vivo study, the discs that were made of CC or Ti were implanted into the subcutaneous layer of BALB/c mice. After skin closure, a suspension including either S. aureus or P. acnes was directly inoculated on the implanted discs. The discs were retrieved and analyzed to determine the number of viable bacteria at 0.5, 1, and 3 days after inoculation.ResultsThe number of viable S. aureus cultured from the CC discs was 0.9 ± 0.2 × 103 CFU/disc, which was significantly lower than the cultured Ti discs (114.8 ± 18.3 × 103 CFU/disc). Moreover, a significantly lower mean number of P. acnes were cultured with CC (1.9 ± 1.2 × 103 CFU/disc) compared with the Ti (180.0 ± 72.1 × 103 CFU/disc). The in vivo infection model testing against S. aureus or P. acnes showed a significantly lower number of viable S. aureus or P. acnes on CC discs than Ti discs. The result was seen at all measured time points.ConclusionCC suppressed S. aureus and P. acnes proliferation compared with Ti in vitro and in an in vivo infection model.Level of Evidence: N/A.Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc.

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