Effect of Propolis Mouthwash on Growth and Sensitivity of Dual-Species Porphyromonas Gingivalis and Staphylococcus Aureus Biofilms (In vitro)

Propolis inhibits the growth of gram-negative and gram-positive bacteria, such as Porphyromonas gingivalis and Staphylococcus aureus, which interact antagonistically. Here, we investigated the effect of 5% propolis mouthwash on the growth, bacterial interactions, and sensitivity of the two bacteria in dual-species P. gingivalis and S. aureus biofilms. Biofilms were formed in 96-well plates by incubating the bacteria for 24 h and assessed using a crystal violet test. The biofilms in 5% propolis mouthwash- and distilled water-treated (control) groups were observed using an inverted microscope after 0, 3, and 24 h of incubation. The proportions of P. gingivalis and S. aureus in the dual-species biofilms were assessed using realtime polymerase chain reaction. The biofilm mass formed by P. gingivalis was higher than that by S. aureus. Propolis mouthwash reduced the formation of dual-species biofilms compared to the control. The proportion of P. gingivalis was higher than that of S. aureus accounting for 9.71% and 1.24% of all bacteria, respectively. The findings reveal the effects of 5% propolis mouthwash on the growth of P. gingivalis and S. aureus and suggest the key roles of the active ingredients in 5% propolis mouthwash and differences in the cell structure of the two bacteria.