日歯周誌 Nihon Shishubyo Gakkai Kaishi (J Jpn Soc Periodontol) 56(4)：406-413, 2014
Takumi Oishi, Chie Fukaya, Shunsuke Kasai, Eitoyo Kokubu,
Atsushi Saito, Kazuyuki Ishihara and Taneaki Nakagawa
The aim of this study was to examine the effect of sitafloxacin (STFX) on an in vitro dental biofilm model. Eradication of periodontal bacteria within the biofilm and formation of a biofilm itself is an important issue in the treatment of periodontal diseases. Periodontal biofilms are often recognized as being composed of polymicrobial aggregates, that are resistant to various antimicrobial agents and disinfectants to which planktonic bacteria are susceptible. STFX is an oral new quinolone antibacterial drug that has a broad antibacterial spectrum, including oral anaerobic bacteria. STFX has been approved for the treatment of respiratory tract and urinary tract infections, as well as for that of odontogenic infections in Japan. In this study, we used a novel microfluidic device, BioFlux, which was designed to run an automated culture flow under the anaerobic condition and is expected to be useful for in vitro oral biofilm experiments. A mixture of Porphyromonas gingivalis ATCC33277 and Streptococcus gordonii ATCC35105 was introduced into the microfluidic channels and then allowed to attach and form a biofilm for a total of two hours at 37℃. The formation of the biofilm on the surface of the channels was observed by microscopy. STFX or azithromycin (AZM) solution was then added to the BioFluxsystem and the continuous flow was resumed for five days under the anaerobic condition. We chose the following drug concentrations：0.65 and 1.30 mg/ml for STFX, and 2.92, 3.95 and 7.90 mg/ml for AZM, calculated based on the concentrations reached in the gingiva and gingival crevicular fluid when STFX and AZM are administered orally in adult patients. After continuous exposure of each drug to the already established biofilm, the rate of viable cells present in the biofilm was quantified by fluorescence microscopy and an image analysis technique using the LIVE/DEADR BacLightTM Kit. We found that each of the drugs decreased the viable cell rate of the co-culture of P. gingvalis and S. gordonii in a dose-dependent manner. Notably, STFX significantly decreased the number of viable cells in the biofilm as compared to AZM (p＜0.05). These results suggest that STFX has the potential to inhibit oral biofilm formation and/or exert bactericidal activity against even those periodontal pathogens that are present in biofilms.