Antibacterial activity of Thymoquinone, an active principle of Nigella sativa and its potency to prevent bacterial biofilm formation

Abstract

Background: Thymoquinone is an active principle of Nigella sativa seed known as "Habbah Al-Sauda" in Arabic countries and "Sinouj" in Tunisia. Bacterial biofilms tend to exhibit significant tolerance to antimicrobials drugs during infections.

Methods: The antibacterial activity of Thymoquinone (TQ) and its biofilm inhibition potencies were investigated on 11 human pathogenic bacteria. The growth and development of the biofilm were assessed using the crystal violet (CV) and the 2, 3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) reduction assay.

Results: TQ exhibited a significant bactericidal activity against the majority of the tested bacteria (MICs values ranged from 8 to 32 μg/ml) especially Gram positive cocci (Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis CIP 106510). Crystal violet assay demonstrated that the minimum biofilm inhibition concentration (BIC50) was reached with 22 and 60 μg/ml for Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis CIP 106510 respectively. In addition our data revealed that cells oxidative activity was influenced by TQ supplementation. In the same way, TQ prevented cell adhesion to glass slides surface.

Conclusion: The ability of TQ to prevent biofilm formation warrants further investigation to explore its use as bioactive substances with antibiofilm potential.

Figure 1

Microscopic visualization of the effect of thymoquinone on four biofilm positives strains cultured on glass slides covers. Prevention of biofilm formation effect of TQ was as followed: For S. aureus ATCC 25923 a, non treated slides; aa, cells supplemented with TQ MIC; aaa, cells supplemented with TQ 2 × MIC. For S. epidermidis CIP 106510, b, positive control (non treated slides); bb, cells supplemented with TQ MIC; bbb, cells supplemented with TQ 2 × MIC.For E. faecalis ATCC 29212, c, non treated slides; cc, cells supplemented with TQ MIC; ccc, cells supplemented with TQ 2 × MIC. For P. aeruginosa ATCC 27853, d, non treated slides; dd, cells supplemented with TQ MIC; ddd, cells supplemented with TQ 2 × MIC.