A Comparative Evaluation of Antimicrobial Effect of Thymus capitatus Ethanolic Extract on the Different Respiratory Tract Infections Isolates

Abstract

Natural components, particularly those derived from medicinal plants, provide a promising source of new antimicrobial agents for the treatment of respiratory infections. In this work, we studied the antimicrobial potency of Thymus capitatus ethanolic extract against nine microorganisms isolated from clinical material obtained from patients admitted to hospitals in Egypt and Germany with infections of the respiratory tract (bacterial sinusitis, laryngitis, pharyngitis and bronchitis) using the disc diffusion assay and minimum inhibitory concentration (MIC) values. All isolates obtained from the Giessen University Clinic (Germany) exhibit susceptibility of different extent to the plant extract tested. The growth inhibition zone diameters for nine strains were in the range of 13–15.5 mm at a concentration of 5 mg/disc. The extract produced large inhibition zones of 14–17 mm diameters for seven microbial strains obtained in Egypt although it failed to inhibit the growth of isolates of Staphylococcus epidermidis and Enterococcus faecalis. In fact, most of the respiratory tract infections isolates from Egypt were generally more susceptible to the ethanolic extract of Thymus capitatus at lower MIC values than those obtained from Giessen University Clinic MIC values. The results of this study suggest that further delineation of bioactive phytomolecules of Thymus capitatus ethanolic extract will improve their potential application for the treatment of respiratory tract diseases.