Antibacterial activity of aqueous infusion and decoction of dried leaves of oregano (Origanum vulgare) on clinical bacterial isolates

Introduction: Oregano (Origanum vulgare) is a common culinary herb that is known to inhibit the growth of several bacterial strains. Aim: To assess the antibacterial effect of crude aqueous infusion and decoction of dried leaves of Origanum vulgare against common clinical isolates. Materials and Method: Crude extracts of Oregano with a standard concentration of 0.2 g/ml, were tested for their antibacterial activity against 10 isolates each of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella typhi, isolated from various clinical samples, by agar well diffusion assay. The standardised antibiotics (Hi Media, India) used for comparing sensitivity pattern were ciprofloxacin (5 μg/disc) for all strains except P. aeruginosa for which gentamicin (15 μg/disc) was used. Results: In the present study, both the aqueous infusion and decoction showed inhibitory potential against 3 out of the 5 organisms tested. Highest activity was noted against Staphylococcus aureus with 8 out of 10 isolates tested being sensitive with wide range of zone of inhibition between 10-19 mm, followed by Escherichia coli, 6 out of 10 sensitive with a zone of 12-16 mm. 3 out of 10 isolates of K. pneumoniae were sensitive with a zone of 7-10 mm. Both infusion and decoction did not show any activity against Salmonella typhi and Pseudomonas aeruginosa. Conclusion: The data presented confirm the antibacterial potential and highlight the promising role of oregano as new lead structure in the search for novel antibacterial agents. Therefore, further experiment involving a larger sample size and extract concentrations is worthy of evaluation. Keywords: Origanum vulgare, Antibacterial activity, Crude extracts, Clinical bacterial isolates