Abstract
This study aimed to evaluate the antimicrobial effect of Thymoquinone (TQ) on four different oral microorganisms. Minimum Bactericidal Concentration (MBC), Minimum Inhibition Concentration (MIC), Broth microdilution, and Well diffusion tests were used to determine the optimum antimicrobial concentrations of TQ against Streptococcus salivarius, Streptococcus oralis, Streptococcus mutans, and Staphylococcus aureus over 1, 3, 6, 12 and 24 h. Chlorhexidine 0.12% was selected as a positive control. The inhibitory effect of TQ on bacterial growth was most noticeable with S. salivarius, while the least affected was S. aureus. TQ’s MBC and MIC for S. oralis and S. aureus were comparable 2 mg/mL and 3 mg/mL, respectively. S. salivarius was most resistant to TQ and displayed a value of 5 mg/mL and 4 mg/mL for MIC and MBC, respectively. The viable count of different strains after exposure to TQ’s MBC values was most noticeable with S. aureus followed by S. oralis and S. mutans, while S. salivarius was least affected. This study emphasized the promising antimicrobial effect of TQ against the four main oral microorganisms. It has a potential preventive effect against dental caries as well as other oral diseases.
Highlights
The oral cavity is inhabited by hundreds of microorganisms of different species, mainly bacteria, forming the oral biofilm
The findings indicated that the microbial activity of TQ was concentration-dependent
There was no bacterial growth for TQ concentrations of 75 and 100 mg/mL
Summary
The oral cavity is inhabited by hundreds of microorganisms of different species, mainly bacteria, forming the oral biofilm. Biofilm formation in the oral cavity can cause multiple different diseases depending on the prominent microorganisms, such as caries, root canal infections, periodontal diseases, and peri-implant diseases, and other gastric intestinal track-related diseases [1,2,3]. Dental caries is an infectious disease that starts with a bacteria-colonized dental plaque. Dental plaque is a sticky, highly hydrated extracellular biofilm that forms on the tooth surface later is colonized by cariogenic bacteria that ferment dietary carbohydrateproducing acid. Despite all the advancements in dental education and oral hygiene awareness, dental caries remains the leading health challenge in most developed countries, where 60–90% of children and most adults suffer from dental caries. On the contrary, developing countries have caries prevalence reported to reach as high as 68% [6]
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