Anti-bacterial Effect of a Cetylpyridinium Chloride Rinse in vitro

Cetylpyridinium Chloride (CPC) is an antibacterial agent broadly used in oral rinse formulation. It is a quaternary ammonium compound with positively charged region, which can interact with negatively charged rinse ingredients, eg. fluoride, phosphate salt, Saccharin, and/or non-ionic surfactant, eg. pluronic. This interaction could lead to reduction of CPC's antibacterial effect. During the development of a new CPC rinse, we found that the degree of ionic impact differs from negative charged molecules. The higher pluronic dosage may cause lower efficacy. The degree of difference can be determined by laboratory bio-methods. Objective: This study was aimed to evaluate in vitro efficacy of a new 0.05% CPC rinse, which was formulated with less ionic interaction and lower pluronic concentration. Method: 1). Bacterial killing assay (BKA) was conducted after incubation of whole saliva bacteria in a rich medium at 37^oC for 24 hr. Bacterial suspension was treated with a rinse for 30 sec. A sequential dilution was made before transferring 0.1 ml of aliquot to a culture plate and incubated at 37^oC for 72 hr. Percent killing was calculated by comparing CFU in rinse treated sample vs. a control. 2). Bacterial growth inhibition assay (GIA) was performed using S. mutans and A. naeslundii. Briefly, bacteria suspension was mixed with the CPC rinse and incubated at 37^oC for 24 hr. Bacterial growth profiles were recorded at O.D. 630nm. Results: In BKA, the CPC rinse showed more than 99% bacterial killing vs. the control. In GIA, CPC rinse exhibited 81% significant growth inhibition vs. the control. Conclusion: This study showed that a new CPC rinse with a less ionic interaction and low pluronic delivers a strong anti-bacteria effect in vitro. This study suggested that the relationship between the degree of molecular interaction and biologic efficacy of CPC rinse could be evaluated via in vitro bio-assays.