Comparison of Antibacterial Efficacy of Probiotic Mouthwash with Chlorhexidine Against Common Oral Pathogens: An In-Vitro Study

Background: The basic method in prevention of oral disorders and hygiene of an oral cavity is control of plaque growth and germ accumulation on teeth and gingivae. Mouthwashes are most common topical solutions against plaque formation. Although there are many antimicrobial agents in use, only a few have shown clinical effectiveness. Furthermore, their long-term use may lead to several side effects. Therefore, utilizing natural antimicrobial agents such as probiotics may be an effective way to overcome the problem. The purpose of the present investigation was to design a mouthwash formulation containing probiotic extract. Methods: Standard strains of 4 main oral pathogenic bacteria, Streptococcus mutans, Streptococcus salivarus, Actinomyces viscosus, and Actinomyces neoslandi were utilized to evaluate the product antimicrobial activity. Lactobacillus casei was cultured in standard medium and its antibacterial effectiveness was evaluated by the spot-test. Each pathogen suspension was inoculated separately on plates containing specific media. Lyophilized probiotic extract (LPE) was prepared in a specific temperature condition and poured in wells. After incubation, the samples growth inhibition zone was measured. Mouthwash formulations containing different concentrations of LPE, Glycerin, and Sorbitol were prepared and based to their physic-chemical properties as well as their long-term stability. The best formulation was chosen and flavorant and sweetener were added. Well-diffusion method was utilized and their mean diameters of growth inhibition was recorded and compared to that of chlorhexidine and a blank Glycerin-Sorbitol solution as positive and negative controls, respectively. Minimum inhibitory concentrations of each formulation were investigated by the macro-dilution method and the formulation with maximum antibacterial activity was determined. Results: Well-diffusion experiment showed that chlorhexidine mouthwash is stronger than 1% - 4% containing LPE formulations, while there was no significant difference between 5% LPE formulation and the positive control (P > 0.05). There was no growth in the inhibition zone. For negative control, MIC studies proved that 5% LPE and chlorhexidine formulations were similar and their maximum and minimum activities were A. neoslandi and S. salivarous, respectively. Conclusions: The findings in the present study proved that the 5% LPE formulation is as effective as the chlorhexidine solution and may be utilized as a natural safe mouthwash.