Post-antibiotic Effects and Post-sub-minimal Inhibitory Concentration Effects of Cetylpyridinium Chloride on Streptococcus gordonii and Streptococcus mutans

Background and Objectives: When an antimicrobial agent is removed after the treatment of bacteria for a short period, it takes a long time for the bacteria to return to normal growth, despite the reduction in the antimicrobial agent concentration. This phenomenon is referred to the post-antibiotic effect (PAE). The PAE of cetylpyridinium chloride, which is a common ingredient in oral mouthwash solutions, has not yet been elucidated. We evaluated the post-antibiotic effect (PAE), post-antibiotic sub-MIC effect (PA SME), and sub-MIC effect (SME) for cetylpyridinium chloride in Streptococcus gordonii, which is known to be an early colonizer of the tooth surface, and Streptococcus mutans, a causative agent of dental caries.

Materials and Methods: After cetylpyridinium chloride was applied to bacteria, PAE, PASME and SME were measured to investigate the time to recovery of bacterial growth.

Results: The mean PAE times for S. gordonii and S. mutans were 1 h and 1.07 h, respectively. When the PA SME was compared with the PAE, the PA SME was longer than the PAE in both S. gordonii and S. mutans.

Conclusion: In this study, it was shown that cetylpyridinium chloride can cause a PAE, PA SME and SME; therefore, this pharmacodynamic effect should be expected in the clinical application of cetylpyridinium chloride.