Antibacterial and resistance-modifying activities of thymoquinone against oral pathogens

Laboratory of Analyses, Treatments and Valorisation of Environmental Wastes and Products, Faculty of Pharmacy, Monastir University, Avicenne Street 5000, Monastir, Tunisia.
Annals of Clinical Microbiology and Antimicrobials (Impact Factor: 2.19). 06/2011; 10(1):29. DOI: 10.1186/1476-0711-10-29
Source: PubMed


The 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.
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 cells accumulation.
TQ 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.
TQ 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.

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Available from: Mahdouani Kacem, Oct 01, 2015
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    • "It is well known that the multidrug-resistance efflux pumps are one of the mechanisms responsible for a bacterial resistance to antibiotics, mostly to tetracyclines (Piddock, 2006). Kouidhi et al. (2011) discovered that Tq is able to cause efflux inhibition and therefore increases the intracellular concentration of 4,6-diamidino-2-phenylindole. Therefore we suggest that this mechanism could also contribute to the combinatory anti-staphylococcal effect of Tq-tetracycline, demonstrated in our experiments. "
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    ABSTRACT: Thymoquinone (Tq) has been reported to potentiate the in vitro growth-inhibitory activity of some antibiotics especially against Staphylococcus aureus. However, it has been shown that Tq vapors can affect the results of susceptibility testing by standard broth microdilution method. Therefore, we made a comparative experiment with and without ethylene vinyl acetate cap mats (EVA capmatTM) on microplates. The results showed significant differences in the minimum inhibitory concentration values and proved this capmat as an effective vapor barrier. Therefore further experiments focused on the in vitro anti-staphylococcal combinatory effect of Tq with oxacillin, penicillin, and tetracycline against various S. aureus strains have been performed by checkerboard method using EVA capmatTM. The combined effect was evaluated according to the sum of fractional inhibitory concentrations (ΣFIC). Synergy was obtained for combination with oxacillin against 3 (ΣFIC 0.263-0.450), with penicillin against 1 (ΣFIC 0.466) and with tetracycline against 2 strains tested (ΣFIC 0.400-0.475). Our results confirm previous reports on the Tq enhancement of anti-staphylococcal activity of antibiotics. Moreover, this is the first report on Tq synergy with oxacillin and penicillin against S. aureus. Our experiments also showed that Tq vapors can affect evaluation of combined effect by checkerboard assay, whereas the use of EVA capmatTM can avoid this.
    Arabian Journal of Chemistry 05/2015; DOI:10.1016/j.arabjc.2015.04.021 · 3.73 Impact Factor
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    ABSTRACT: The oil of black seed Nigella sativa has been used as a folk medicine to treat a number of physiological disorders such as epilepsy, gastric problems, allergic conditions and various hepatobiliary ailments. Despite being unaware of the underlying phenomena for the cure of these diseases, people especially in the Mediterranean region have been using this ancient herb since ages. Researches in the 20th century conducted with the aim of tracking molecular pathways of antioxidant and antiinflammatory mechanisms disclosed a great deal of information pertaining to the structuralactivity relationships. Rigorous studies revealed that the major active constituent of Nigella sativa oil NSO is Thymoquinone THQ which exerts the majority of pharmacological actions observed by the essential oil. Since then, a large number of investigator groups have identified numerous molecular pathways of almost all major diseases which can be cured by THQ. Being a phytochemical, THQ has a high lipophilicity which makes it a poorly soluble agent in aqueous fluids restricting its systemic bioavailability. Also, THQ is highly light and heatsensitive which further complicates its successful formulation for drug delivery. This review thus offers an insight to adequately comprehend the large number of pharmacological actions along with general mechanisms and major molecular targets pertaining to THQ. Additionally, a section dealing with the application of nanotechnological approaches to appropriately deliver the drug to its intended site of action has been elaborated.
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    ABSTRACT: Thymoquinone (TQ) is a plant extract that has been shown to have antimicrobial, anti-inflammatory, and antioxidant effects. Because of these activities, the authors hypothesized that TQ would reduce inflammation and oxidative stress and accelerate wound closure in a rat model of deep second-degree burns. For the purposes of this study, 40 Sprague-Dawley rats were divided into five groups of eight rats each. Group 1 was the control group, group 2 was the silver sulfadiazine group, group 3 was treated with systemic TQ, group 4 received topical TQ, and group 5 was administered topical and systemic TQ. After the deep second-degree burn damage was created, daily dressing changes and TQ administration were continued in the study groups for a period of 21 days. Systemic TQ was administered intraperitoneally at a dose of 2 mg/kg/day, whereas the topical treatment was applied using a 0.5% solution. The changes in the wound site were observed macroscopically, histopathologically, microbiologically, and biochemically in all groups. The smallest necrotic areas were observed at the end of the study in the groups that were administered a combination of systemic and topical TQ, or solely topical TQ (6.05 ± 1.5 cm and 6.7 ± 0.47 cm, respectively), whereas the largest necrotic areas were observed in the control group (11.2 ± 1.1cm). The total antioxidant state levels in the control group were significantly lower than in the other groups (P < .05), whereas the total oxidative stress levels were lower in the TQ groups compared with the control group (P < .05). The lowest bacterial counts were observed in the groups treated with both topical and systemic TQ (P < .05). TQ given systemically and/or topically reduced inflammation and oxidative stress and accelerated the rate of wound closure or reepithelialization.
    Journal of burn care & research: official publication of the American Burn Association 06/2013; 34(5). DOI:10.1097/BCR.0b013e31827a2be1 · 1.43 Impact Factor
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