Antimicrobial profile of essential oils extracted from wild versus cultivated Origanum ehrenberjii against enteric bacteria

Abstract

Introduction: The role of Origanum ehrenberjii against bacteria that cause enteric diseases is well known. Salmonella and Enterococcus cause high rates of enteric infections around the world. The aim of this study was to extract essential oils from cultivated and naturally growing O. ehrenberjii, compare the chemical profiles of the extracts and estimate their antimicrobial efficacy against enteric pathogens. Methodology: Sixteen compounds were recovered consistently from essential oils extracted from O. ehrenberjii of wild and cultivated origin. The chemical profiles were determined using GC-MS. Safety of the essential oils was determined by observing mortality of chicks after intramuscular administration of the oils. The antimicrobial efficacy of the oils against the enteric pathogens was determined by the Kirby-Bauer Single Disk Diffusion assay. Results: The levels of thymol, carvacrol, para cymene and γ-terpinene were significantly different in the two oils. A significant difference in in vitro antimicrobial activity of the two oils against Salmonella enterica serovar Typhimurium was observed. Intramuscular administration of the two oils in one day-old chicks resulted in significant differences in mortality of 60% vs. 5% (p < 0.05) for wild and cultivated herbs respectively, reflecting the higher safety of the cultivated herb due to the differences in the levels of certain active ingredients. Conclusions: The chemical profile of essential oil of wild vs. cultivated O. ehrenberjii differ significantly at compound level, suggesting the reason for their significant difference in efficacy against Salmonella enterica serovar Typhimurium, and also significant differences in the toxicity of the two oils.