Effect of Amoxicillin on Oral Microcosms in a Dynamic Reactor.

Objectives: To validate growth of oral microcosm biofilms from subgingival plaque in a dynamic bioreactor model. To evaluate the anti-microbial effect of amoxicillin in a simulated environment on oral microcosm biofilms grown under dynamic and high-shear conditions in an in vitro model.
Methods: Biofilms were grown for 4.5 days on polycarbonate coupons in two (control and experimental) Centre for Disease Control (CDC) biofilm reactors under similar conditions from pooled subgingival plaque collected from six patients. Subsequently, amoxicillin was infused into the experimental reactor simulating the pharmacokinetic profile from the standard 500 mg thrice-daily dosing regimen, for five days. Amoxicillin-treated and control biofilms from each reactor were assessed using live/dead staining, scanning electron microscopy and quantitative polymerase chain reaction.
Results: Live dead staining showed an increased number of dead bacteria in the amoxicillin treated biofilms compared to the controls. However, live bacteria persisted in the inner sections of the confocal images of the amoxicillin treated biofilms, indicating reduced penetration of the antimicrobial into the biofilms. C. rectus, T. forsythia, A. actinomycetemcomitans, E. corrodens and P. anaerobius were undetected in the amoxicillin treated biofilms at 96 and 120 hrs, in contrast to the control biofilms.
Conclusions: This novel study evaluated the effect of amoxicillin in the bioreactor itself thus simulating the pharmacokinetics of amoxicillin. Amoxicillin treatment results in a reduction of specific bacteria in oral biofilms, however, it was unable to eliminate all of the bacteria in oral microcosms.