In-vitro Antibacterial Efficacy of Experimental Cetylpyridinium Chloride (CPC) Containing Mouthwashes

A number of existing studies have examined the antibacterial efficacy of mouthwashes. Of particular interest is the ability of a mouthwash to kill bacteria during the relatively short time period for which mouthwashes are indicated for use, approximately 30s. Objective: The objective of this study was to examine the ability of four Cetylpyridium Chloride (CPC) containing mouthwashes to kill planktonic bacteria in an in-vitro short exposure assay. Methods: This study was conducted on two bacterial species commonly found in the oral cavity: Aggregatibacter (Actinobacillus) actinomycetemcomitans (ATCC #43717) and Streptococcus mutans (ATCC #25175). Mouthwashes included three experimental 0.075% CPC formulas: two without alcohol but with different excipients and one with 6% alcohol. In addition, one 0.05% CPC alcohol-free formula and a negative control alcohol-free placebo formula were included. Bacteria were exposed to the test mouthwashes for 30 s and then washed thoroughly, serially diluted and plated on appropriate media to determine viable bacterial counts. Viable counts were converted to a log reduction in bacteria relative to the placebo. Results: All CPC-containing mouthwashes significantly reduced bacterial counts versus the placebo formula. Each of the 0.075% CPC-containing formulas gave over a 4 log reduction in colony forming units (CFUs) relative to the placebo mouthwash against both organisms tested. The 0.05% CPC-containing formula gave a greater than 3 log reduction in S. mutans and more than a 1.5 log reduction in A. actinomycetemcomitans as compared to the placebo mouthwash. Conclusion: Experimental CPC mouthwash formulas containing 0.075% CPC, with or without alcohol produced statistically significant 99.99% reductions (p<0.05) in planktonic A. actinomycetemcomitans and S. mutans, compared to negative control placebo formula. Experimental CPC-containing formulas with 0.075% CPC, with or without alcohol produced a statistically significant (p<0.05) reduction in planktonic bacteria as compared to an alcohol-free mouthwash with 0.05% CPC.