To evaluate the effects of thymoquinone (TQ) on biofilm formation, hemolysis, hydrogen sulfide (H2S) production and expression of virulence factors of Fusobacterium nucleatum and Porphyromonas gingivalis.
Reference strains of F. nucleatum ATCC 25586 and P. gingivalis A7436 were tested in our study. The minimum inhibitory concentration (MIC) of TQ was determined by broth microdilution method. The impacts of TQ on virulence properties of the periodontal bacteria including biofilm formation, hemolysis and H2S activities were studied. Quantitative RT-PCR was performed to evaluate the expression levels of key virulence factors including outer membrane proteins (aim-1, fadA) in F. nucleatum as well as cysteine proteinases or gingipains (rgpA, rgpB, kgp) and fimbriae (fimA, mfa1) in P. gingivalis.
The MIC of TQ were 12.5 and 1.56 μg/mL in F. nucleatum and P. gingivalis, respectively. The sub-MIC concentrations of TQ could prevent biofilm formation and hemolysis activities of both bacteria. TQ also inhibited H2S production which is highly associated with oral malodour. Scanning electron microscopy revealed that TQ could disrupt bacterial membrane and led to cell lysis. Furthermore, TQ reduced the expression of major virulence factors tested in F. nucleatum and P. gingivalis.
The TQ had potent antibacterial effect and could attenuate virulence properties of F. nucleatum and P. gingivalis. Therefore, TQ has the potential to be developed and used in periodontal treatments, especially to prevent the progression of periodontitis.