In Vitro Antibacterial Effects of Five Volatile Oil Extracts Against Intramacrophage Brucella Abortus 544

Background: Brucella abortus is a gram-negative facultative intracellular bacterium that can cause a highly contagious disease in sheep, goats, cattle and one-humped camels. It is responsible for one of the most important zoonosis in human. The aim of this study was to evaluate the role of Mentha piperita, Origanum majorana, Citrus lemon, Cinnamomum verum and Myristica fragrans essential volatile oil extracts on human macrophages infected by B. abortus 544. Methods: Essential volatile oil extracts from M. piperita, O. majorana, C. lemon, C. verum and M. fragrans were extracted. Human macrophages were cultured at a density of 2×105 cells per well in sterile 96-well microtiter plates, and infected with B. abortus 544 at a ratio of 1:100 bacteria/cell. Then essential volatile oil extracts were added at a concentration of 1%. At specified times; cells were washed, lysed with 0.1% Triton, and plated on 2YT agar to determine the number of intracellular bacteria. Results: Cinnamomum verum volatile oil at a concentration of 1% had the highest antibacterial activity against B. abortus 544 inside human macrophages. Its inhibitory effect observed from 24 h and continued till 144 h after the infection. Moreover, C. verum (0.1%) in combination with 1% concentration of M. piperita, O. majorana, C. lemon or M. fragrans volatile oil extracts produced a synergistic inhibitory effect against B. abortus 544. Conclusion: The results indicate that, among the five selected oil extracts, C. verum volatile oil applied either separately or in combination with other oil extracts had the most effective antimicrobial activity against Brucella.