Differences in the antibacterial efficacy of honey against oral and non-oral bacterial pathogens in artificial human saliva

Abstract Mouthwash is used as an adjunct to mechanical oral hygiene, and this combination is widely utilised among the older population. The aim of the study was to determine the antibacterial efficacy of over-the-counter mouthwashes and honey samples, including manuka honeys, against oral and non-oral bacterial pathogens in the presence of artificial human saliva. Five over-the-counter mouthwashes, three honey samples (honeydew, acacia, and linden), and manuka honeys with different contents of methylglyoxal were used in this study. The antibacterial activity of the tested mouthwashes/honeys in the absence or presence of human artificial saliva was determined with a minimum inhibitory concentration assay. The mouthwashes exhibited higher efficacy against oral bacteria ( Streptococcus mutans , Streptococcus sobrinus , and Rothia dentocariosa ) but were less effective against non-oral bacteria ( Pseudomonas aeruginosa , Escherichia coli , and Proteus mirabilis ) except for Staphylococcus aureus . Artificial saliva significantly decreased the antibacterial activity of mouthwashes against oral pathogens but not non-oral pathogens. The most effective honey against all tested bacteria was manuka honey and its efficacy was enhanced with increasing amount of methylglyoxal. Artificial saliva did not affect the antibacterial activity of all honeys against oral bacteria. However, it significantly reduced the antibacterial activity of honey samples except manuka honey against non-oral pathogens. Furthermore, a significant reduction of glucose oxidase activity and a subsequent decrease in hydrogen peroxide content were observed in non-manuka honeys. In conclusion, mouthwashes and honeys vary in their antibacterial effect against oral and non-oral bacteria, and the observed effect can be influenced by human saliva.