Antimicrobial action of GEC to evaluate the possible clinical application

Objective: The oral cavity contains almost 700 species microorganisms. It is well known that remarkable increases in these microorganisms cause not only oral infections such as dental caries and periodontal diseases, but also systemic diseases such as infective endocarditis, atherosclerosis and aspiration pneumonia. Consequently, it is a very important to control the numbers of oral microorganisms in order to suppress these diseases. Gel entrapping catechin (GEC; Meiji-Dairies, Tokyo), which is compounded from a mixture of different types of catechin, has been prepared to reduce the number of oral pathogenic microorganisms of patients in need of nursing care. We examined the antimicrobial action of GEC against oral microorganisms and attempted to the possibility for clinical application.

Methods: Twenty-seven strains of oral microorganisms were employed in this study. The antimicrobial action was tested in terms of forming an inhibition-zone with or without GEC after incubation using the modified agar diffusion method. The catechin residual quantity in GEC after washing was compared with the catechin solution. The effect of calatase on antimicrobial action was also examined.

Results: The antimicrobial action of GEC was the same as or greater than that of epigallocatechin gallate as a positive control. Microbial inhibition zones were found for all of the strains of Actinomyces naeslundii, Streptococcus mutans, Candida albicans and periodontopathic bacteria. By contrast, no inhibitory effect was observed for oral streptococci which play an important role in indigenous oral flora. The quantity of catechin in GEC after washing was remarkably higher than that in solution. Interestingly, zones of A. naeslundii and S. mutans were disappeared by the presence of catalase.

Conclusions: These results suggest that GEC could be useful for control the number of oral microorganisms and clinical application.