Study of antibacterial effect of total hydroalcoholic extract of Thymus daenensis and Lavandula officinalis on Listeria monocytogenes, an agent of food spoilage, using microdilution

摘要

Background: Listeria monocytogenes is an important bacterial agent of food spoilage and cause of listeriosis. Recently, plants have been increasingly considered as alternatives to chemical drugs for preserving foods. Therefore, it is highly important to study their antibacterial effects. This study was conducted to investigate the antibacterial effect of Thymus daenensis and Lavandula officinalis on L. monocytogenes. Extraction was done by maceration using ethanol and concentration performed by rotary concentrator. Minimum inhibitory concentration (MIC) was examined by broth micro-dilution according to McFarland Equivalence (CFU/mL 105). To determine minimum bactericidal concentration (MBC), all the wells without opacity were cultured on Mueller-Hinton agar. Total hydroalcoholic extract of T. daenensis and L. officinalis had a positive effect on L. monocytogenes and, at certain concentrations, could inhibit the bacterial growth. The best inhibitory effect on bacterial growth was obtained for T. daenensis extract at 16 μg/mL. Furthermore, this extract had the highest bactericidal effect on L. monocytogenes. Regarding the findings of this study, the extracts of T. daenensis and L. officinalis could be used as antibacterial agents in food and pharmaceutical industries.