Antibacterial Activity of Essential Oils of <i>Thymus serpyllum</i> L. and <i>Thymus marschallianus</i> Willd.

Introduction. Plant essential oils are supposed to be applied for local treatment of infectious focuses. Aim. The aim of this study was evaluation of antimicrobial activity of essential oils of Thymus serpyllum L. and Thymus marschallianus Willd., widely distributed in the Saratov region. Materials and methods. Antimicrobial activity of the essential oils was determined by a serial dilution test at the microbial number of 5 × 10 5 CFU/ml against 6 strains of Staphylococcus aureus , including S. aureus FDA 209P and five clinical, 2 strains of Escherichia coli – E. coli ATCC 25922 and one clinical, two strains of Pseudomonas aeruginosa – P. aeruginosa ATCC 27835 and one clinical. Results and discussion. The bactericidal minimal inhibitory concentrations (MICs) of essential oil of T. serpyllum were determined for all strains of staphylococci (for 5 – 1097,5, for 1 – 2195 µg/ml). The bacteriostatic MICs were determined for 3 strains (for 2 – 548,75, for 1 – 1097,5 µg/ml). MICs of the T. marschallianus essential oil were bactericidal for all strains of S. aureus (120 for 5 and 480 µg/ml for 1 strain). For all test strains of gram-negative bacteria MICs of the essential oils of both species were bactericidal and amounted to 1097 and 960 µg/ml. Considering the chemical composition of the oils by thymol and its isomers, MIC 50 of T. marschallianus and T. serpyllum for the test staphylococcal strains amounted 108,89 and 496,59, for the test strains of gram-negative bacteria 683,91 and 783,43 µg/ml respectively. Conclusion. According to the values of MIC 50 antistaphylococcal activity of the essential oils of T. marschallianus was significantly higher than this activity of the essential oils of T. serpyllum .