Antibacterial and resistance-modifying activities of thymoquinone against oral pathogens

Abstract

BackgroundThe presence of resistant bacteria in the oral cavity can be the major cause of dental antibiotic prophylaxis failure. Multidrug efflux has been described for many organisms, including bacteria and fungi as part of their drugs resistance strategy. The discovery of a new efflux pump inhibitor could extend the useful lifetime of some antibiotics.MethodsIn 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 cells accumulation.ResultsTQ induced a selective antimicrobial activity. Its synergic effect resulted in at least a 4-fold potentiation of the tested antibiotics and antiseptic. In addition, TQ inhibited the DAPI efflux activity in a concentration-dependent manner. The rate of DAPI accumulation in clinical isolates was enhanced with TQ (0 to 200 μg/ml). There is also a decrease in loss of DAPI from bacteria in the presence of TQ. The concentration causing 50% of DAPI efflux inhibition after 15 minutes was approximately 59 μg/ml for Pseudomonas aeroginosa and 100 μg/ml and Staphylococcus aureus respectively.ConclusionsTQ possesses a selective antibacterial activity against oral bacteria. It is therefore suggested that TQ could be used as a source of natural products with resistance-modifying activity. Further investigation is needed to assess their clinical relevance.

Antibacterial and Resistance Modifying Activities of Nigella sativa Essential Oil and its Active Compounds Against Listeria monocytogenes

“…These results support previous studies which reported an effective antibacterial activity of N. sativa essential oil (22), thymoquinone (23) and carvacrol (24) against Gram-positive bacteria. DMSO and EtOH as diluents did not show any inhibitory effect on the growth of the strains.…”

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“…20,[23][24][25][26][27] Furthermore, the antibacterial activity of N. sativa seed extract and its constituents against some strains of Streptococcus associated with dental caries has been reported as well. 14,28 Consistent to the results of previous studies, the present study demonstrated a strong growth inhibition and bactericidal activity of DLBS1355 o/w emulsion against S. mutans and S. sanguis, with a slightly higher activity on S. sanguis.…”

“…The antibacterial effect synergism of N. sativa seed essential oil with antibiotic was reported in several previous studies, therefore it may be used in combination with antibiotic. 28,46 Further investigation is needed in order to investigate the cytotoxic effect of N. sativa seed o/w emulsion regarding to human use.…”

Analysis and Antibacterial Activity of <i>Nigella sativa</i> Essential Oil Formulated in Microemulsion System

“…This compound is a phyto-quinone present only in the EO of N. sativa. One of the most important antimicrobial characteristics of TQ is its ability to modify the resistance of bacteria to antibiotics by acting as efflux pump inhibitor 30 . Efflux pumps are proteins in the cell membrane of the bacteria that extrude the antimicrobial agents outside the cell 31 .…”