A Study of Antibacterial Effect of Nigella sativa Seed Extracts on Bacterial Isolates from Cases of Wound Infection

Background: With an increasing trend of pathogenic bacteria developing resistance to the existing drugs, there is a need for newer therapeutic measures. Nigella sativa seeds and oil have been used for decades as Ayurveda, Unani Tibb and other forms of traditional medicine for various disorders. Thymoquinone is one of the active components of the N. sativa seeds.

Objective: The present study determines the antibacterial effect of crude methanolic extract N. sativa seeds and thymoquinone against bacteria causing wound infection.

Methods: Samples obtained from cases of wound infection received at a Microbiology laboratory attached to a tertiary care hospital over a period of six months were included in the study. The antibacterial effect of crude methanolic extract of N. sativa seeds was determined by the Punch Well method. The minimum inhibitory concentration (MIC) of thymoquinone against bacteria isolated from cases of wound infection was determined by the Micro Broth Dilution technique.

Results: A total of 60 isolates were collected from 60 samples of wound infection. By the Punch Well method, Staphylococcus aureus showed varying zones of inhibition whereas all gram-negative bacilli and Enterococcus faecalis did not show any zone of inhibition. Thymoquinone showed good antibacterial activity against S. aureus with MIC values ranging from 2-8μg/ml for most of the isolates. Uniformly, MIC of thymoquinone against all gram-negative bacilli and E. faecalis was >128μg/ml, p<0.001. It was found that methicillin-resistant S. aureus (MRSA) isolates showed higher MIC than methicillin sensitive S. aureus (MSSA) isolates p<0.05.

Conclusion: Antibacterial activity of thymoquinone was very good against S. aureus but showed limited activity against Enterobacteriaceae members and E. faecalis isolated from patients with wound infection. Thymoquinone may be considered a potential antibacterial agent against wound infection caused by S. aureus.