Oral Bacterial Drug Resistance Against New Antibacterial Monomer Dimethylaminohexadecyl Methacrylate

Objectives: To date there are only two publications studying the drug-resistance of quaternary ammonium monomers against oral bacteria; both tested planktonic bacteria for 10 passages, and neither tested biofilms on resins. Objectives: To investigate the drug-resistance of Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) against dimethylaminohexadecyl methacrylate (DMAHDM), and to evaluate biofilms on resins with repeated exposures for 20 passages for the first time.
Methods: DMAHDM, dimethylaminododecyl methacrylate (DMADDM) and chlorhexidine (CHX) were tested with planktonic bacteria. Biofilms were grown on a resin containing 3% DMAHDM. Minimum-inhibitory concentrations (MIC) were measured. To detect drug-resistance, the survived bacteria from the previous passage were used as inoculum for the next passage for repeated exposures.
Results: S. gordonii developed drug-resistance against DMADDM and CHX, but no resistance against DMAHDM (mean ± SD; n = 3). Biofilm colony-forming units (CFU) on DMAHDM-resin was reduced by 3-4 log when compared to that without DMAHDM (mean ± SD; n = 3). There was no reduction in antibacterial potency for DMAHDM-resin from passages 1 to 20 (p > 0.1). No drug-resistance to DMAHDM was detected for all three bacterial species.
Conclusions: This study showed that DMAHDM induced no drug-resistance, and DMAHDM-resin reduced biofilm CFU by 3-4 log, with no significant change from 1 to 20 passages. DMAHDM with potent antibacterial activities and no drug-resistance is promising for dental applications.