Susceptibility of oral bacterial biofilms to antimicrobial agents

There is great interest in the use of antimicrobial agents for the prevention and treatment of plaque-related oral diseases and many publications have reported the results of studies in which the minimum inhibitory concentrations of agents for cariogenic and periodontopathogenic bacteria have been determined. However, such data are relevant only to situations where the organisms of interest are in aqueous suspension, whereas in caries and the inflammatory periodontal diseases the target organisms are in the form of biofilms. On the basis of studies with medically important bacteria, it has been established that bacteria in biofilms are invariably less susceptible to antimicrobial agents than their planktonic counterparts. Therefore, in the laboratory assessment of agents which may be suitable for treating plaque-related diseases, the target organisms should be in the form of biofilms. While laboratory evaluation of chemical agents for the prevention of plaque formation has usually employed biofilm-based models, the search for antimicrobial agents effective in the treatment of plaque-related diseases has not. Therefore, there are few data available regarding those characteristics of antimicrobial agents (e.g., their biofilm eliminating concentrations or biofilm killing concentrations) that could be used to judge their suitability for treating plaque-related diseases. In this review the limited information available concerning the antimicrobial susceptibility of oral bacteria in biofilms is presented.