Effects of the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) on bacterial viability and metabolism

The antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) is a strong bactericide when unpolymerized and has the potential to be utilized in various resinous biomaterials. To analyze the antibacterial characteristics of this monomer in detail, the ability of high concentrations of unpolymerized MDPB to kill Streptococcus mutans in planktonic or biofilm forms within a short time-period of contact, and the inhibitory effects of low concentrations of MDPB on the metabolic function of S. mutans, were examined. High concentrations of MDPB showed effective killing of planktonic and biofilm S. mutans cells within 60 s, and complete killing was obtained by contact with 1,000 mu g ml-1 of MDPB for 60 s. At a concentration of 4-8 mu g ml-1, MDPB demonstrated growth inhibition, inducing elongation of the lag phase and of the doubling time, when the bacterial number was low. Inhibition of the production of acid from S. mutans by 8 mu g ml-1 of MDPB may have been caused by the inhibition of lactate dehydrogenase activity. At high concentrations, MDPB is lethal to both planktonic and biofilm forms of S. mutans in a short time-period, and at low concentrations, MDPB inhibits metabolic enzymatic activity.