Effect of Macrolides on Prevotella intermedia Biofilm on Titanium Implants

Objectives: Prevotella intermedia, a gram negative black-pigmented anaerobic rod, is known as one of periodontopathic bacteria in the oral cavity. Recent studies indicate that this organism acts as an initial colonizer on the tooth surface. This study was performed to examine whether P. intermedia can form so-called single-species biofilm on titanium implants and whether macrolides at 1/2 MIC inhibit the biofilm formation of this organism. Methods: Three different P. intermedia strains, 17 (exopolysaccharide producing strain), 17-2 (a variant strain without exopolysaccharide production obtained from strain 17) and ATCC 25611 (type strain for P. intermedia without exopolysaccharide production) were used in this study. The behaviors of these organisms on titanium discs and on titanium implant fixtures vertically places in bacterial cultures were observed by scanning electron microscopy. The inhibitory effects of macrolides (erythromycin and clarithromycin) against P. intermedia biofilm formation on the implant fixture were compared to those of other protein inhibitors (streptomycin and tetracycline). Results: ATCC 25611 and, to a lesser extent, strain 17 adhered to the titanium disc but strain 17-2 did not. When the titanium fixture in culture medium was inoculated with a mixed culture of ATCC 25611 and strain 17, thick biofilm structures with a dense meshwork were formed although these strains could not construct apparent biofilm structures on the fixture individually. The biofilm formation was reduced by the proteins inhibitors at 1/2 MIC. The effects of macrolides were relatively stronger than those of streptomycin and tetracycline. Conclusion: P. intermedia can form biofilm on titanium dental implants when adhesive cells and exopolysaccharide producing cells collaborate with each other. Macrorides at 1/2 MIC had inhibitory effects on the biofilm formation of P. intermedia.