Antibacterial and Resistance - Modifying Activities of Thymoquinone Against Oral Pathogens |

ABSTRACT:

Background: The presence of resistant bacteria in the oral cavity canbe the major cause of dental antibiotic prophylaxis failure. Multidrug effluxhas been described for many organisms, including bacteria and fungi as part oftheir drugs resistance strategy. The discovery of a new efflux pump inhibitorcould extend the useful lifetime of some antibiotics. Methods: In this study, the MICs of thymoquinone (TQ),tetracycline and benzalkonium chloride (BC)   were  determined in  absence  and in  presence  of a  sub-MIC  doses of thymoquinone (1/2 MIC). In addition the 4,6-diamidino-2-phenylindole(DAPI) efflux assay was carried out to determine the effect of TQ on DAPI cellsaccumulation. Results: TQ induced a selective antimicrobial activity. Itssynergic effect resulted in at least a 4-fold potentiation of the testedantibiotics and antiseptic. In addition, TQ inhibited the DAPI efflux activityin a concentration-dependent manner.  Therate of DAPI accumulation in clinical isolates was enhanced with TQ (0 to 200µg /ml). There is also a decrease in loss of DAPI from bacteria in the presenceof TQ. The concentration causing 50% of DAPI efflux inhibition after 15 minuteswas approximately 59 µ g/ml for Pseudomonasaeroginosa and 100 µ g/ml and Staphylococcusaureus respectively. Conclusions:  TQpossesses a selective antibacterial activity against oral bacteria. It istherefore suggested that TQ could be used as a source of natural products withresistance modifying activity. Further investigation is needed to assess theirclinical relevance.