Antimicrobial activity of novel mouthrinses against planktonic cells and biofilms of pathogenic microorganisms

Background: Oral diseases pose major public health problems on a global scale. Such diseases have considerable impact on individuals and communities by causing pain and suffering, impairment of function and reduced quality of life. The objective of this study was to evaluate the antimicrobial activity of five mouthrinses against a variety of microorganisms associated with infections of the oral cavity and other body sites. Methods: Mouthrinse formulations were Chlorhexidine (0.2%), Citrox (1%; PerioplusTM)/Hyaluronic acid (0.2%)®, Chlorhexidine (0.2%)/Citrox (1%; PerioplusTM), Chlorhexidine (0.2%)/Phenoxetol (0.1%)® and Citrox (1%; Oralclens)TM (Oraldent Ltd; UK). The test microorganisms were the bacteria, Actinomyces viscosus ATCC 1598; Actinomyces odontolyticus NCTC 9935, Clostridium difficile R8651, Prevotella intermedia NCTC 13070T, Prevotella denticola R20771, Porphyromonas gingivalis NCTC 11834T, Streptococcus gordonii ATCC 10558T, Streptococcus sanguinis NCTC 7863, and the fungi, Candida albicans ATCC 90028, Candida dubliniensis CD36, Candida krusei ATCC 6258, Candida glabrata ATCC 2001, Candida tropicalis ATCC 750 and Candida parapsilosis ATCC 22019. Determination of mouthwash antifungal and antibacterial properties was done using a microtitre plate assay. In vitro biofilms were constructed using 96-well plates and exposed to a range of mouthrinse concentrations. The minimum biofilm eradication concentration (MBEC) was established by examining subsequent re-growth of biofilm cells. Results were compared with the minimum inhibitory concentrations (MICs) obtained for planktonic cells cultured in 96-wells plates in various mouthrinse concentrations. Results: Planktonic cells of aerobic microorganisms were inhibited by all mouthrinses at concentrations ≤2% (v/v) of the stock preparation. Chlorhexidine (0.2%)/Citrox (1%)TM had the highest antimicrobial activity, followed by Citrox (1%)TM, 0.2% Chlorhexidine, Chlorhexidine (0.2%)/Phenoxetol (0.1%)® and Citrox (1%)/Hyaluronic acid (0.2%)®. Some anaerobic bacteria (Actinomyces odontolyticus, Clostridium difficile, Prevotella intermedia) exhibited higher MICs for all 5 mouthwashes. There was a noticeable increase (up to 16-fold) in tolerance to the mouthwashes by the majority of aerobic microorganisms when the minimum biofilm eradication concentration was compared to the minimum inhibitory concentration. Conclusion: The results highlight enhanced antimicrobial activity using a combined preparation of Chlorhexidine/Citrox compared with Chlorhexidine alone.