Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P2. Methylene blue is an effective disclosing agent for identification of bacterial biofilms on spinal implants

BACKGROUND CONTEXT Tenacious bacterial biofilms pose a major challenge in treating deep spine infections. Biofilms provide bacteria substantial protection against antimicrobial agents, the host immune response, and are invisible to the naked eye. Biofilms are notoriously difficult to eradicate, and to that end, methylene blue has shown promise as a biofilm disclosing agent in the arthroplasty literature in both in vitro and in vivo settings. PURPOSE The objective of the present study was to assess the intensity of methylene blue staining at varying concentrations as a biofilm disclosing agent in vitro for common biofilm forming bacterial infections and to determine performance characteristics across a range of spine implant materials. STUDY DESIGN/SETTING Microbiology. METHODS S. aureus biofilms were grown to maturity in bioreactors according to established lab protocol on titanium, cobalt chromium, and polyetherketone (PEEK) wafers. Biofilms were stained with 0.05% and 0.01% methylene blue solutions for 5-minutes and then washed with normal saline for 1-minute. Gross images were obtained to compare the visual sensitivity of the blue dye at different dilutions. Scanning electron microscopy was performed to confirm the presence or absence of biofilm on methylene blue stained areas. Images were compared to controls. RESULTS S. aureus biofilms were grown for 7days on double sided titanium, cobalt chromium, and PEEK wafers (n=4 each). There appeared to be a visible dose – dependent relationship based on the staining and dye concentration. At each dilution, biofilms demonstrated visible blue staining after immersion in methylene blue solution; however, blue dye was visible only where biofilms were present as confirmed by SEM. There was no evidence that methylene blue was able to stain titanium, cobalt chromium, or PEEK. CONCLUSIONS Methylene blue functions as an effective disclosing agent for S. aureus biofilm in vitro. Currently, there are no techniques for identifying bacterial biofilm in vivo once it has formed. Given the low cost, favorable safety profile and FDA approval, methylene blue may be considered a first-in-class agent for disclosure of biofilm and may allow surgeons to see biofilms on implants and host tissue in vivo. In so doing, it may allow for efforts at eradicating these biofilms once visualized. Additional work is needed to further elucidate this concept.