Antibacterial Activity of Thymus pubescens Methanolic Extract

During the last two decades, various medicinal plants have been studied for their possible antimicrobial activity to discover new antimicrobial agents capable of resolving problems such as the development of drug resistance in pathogenic microorganisms as well as the side effects of some present antibiotics. In this study, the antibacterial activity of methanolic extract of T. pubescens (rich in flavonoids) was investigated.

The aerial parts of the plant were collected from Alvand mountainside (Hamadan, Iran) in May 2005 and identified by Hamadan Natural Sources Organization. The air-dried plant materials were ground to fine powder and then extracted by soxhelet apparatus using methanol. The extract was tested at a concentration of 100 mg/ml against a panel of Gram-positive and Gram-negative bacteria using the disk diffusion technique. This methanolic extract demonstrated antibacterial activity against Gram-positive bacteria including Staphylococcus aureus, Methicillin-resistant S. aureus (MRSA), Streptococcus pyogenes, Enterococcus faecalis, Vancomycin-resistant E. faecalis (VRE) and Micrococcus luteus, and produced inhibition zones with 8-16 mm diameters. However, it showed no activity against Gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa and Salmonella spp. Minimum concentrations (MC) of the extract forming a clear zone were determined against susceptible bacteria. MC₉₀ of the extract against 10 MRSA strains tested was 1.56 mg/ml, indicating its good activity against this important nosocomial pathogen. T. pubescens seems to be a good candidate for further phythochemical studies in an attempt to find new chemical entities combating resistant bacteria.