In-vitro evaluation of the antibacterial activity of the essential oils of Micromeria barbata, Eucalyptus globulus and Juniperus excelsa against strains of Mycobacterium tuberculosis (including MDR), Mycobacterium kansasii and Mycobacterium gordonae

Background: Mycobacterium spp. are responsible for several diseases, particularly in immunocompromised populations. The spreading of the resistance to antimycobacterial drugs is a significant problem to the public health and requires to find out a new and innovative alternative for the treatment of drug resistant mycobacterial strains. In this study, the antimycobacterial activity of Micromeria barbata, Eucalyptus globulus and Juniperus excelsa essential oils extracted from Lebanese plants was investigated against selected Mycobacterium spp. strains. Methods: Several dilutions of the three aforementioned essential oils were studied for antimycobacterial activity against four Mycobacterium spp. strains: Mycobacterium tuberculosis subsp. tuberculosis (ATCC® 27294™), multidrug-resistant M. tuberculosis (CMUL 157), Mycobacterium kansasii Hauduroy (ATCC® 12478™) and Mycobacterium gordonae Bojalil et al. (ATCC® 14470™). Results: Even with high dilutions, all tested essential oils showed a high antimycobacterial activity against targeted strains. Our data showed that M. barbata, E. globulus and J. excelsa essential oils totally inhibit the mycobacterial growth whatever the tested strains for the dilution 1/250, 1/100 and 1/250, respectively. Conclusion: To our knowledge, this is the first study regarding the antimycobacterial activity of essential oils in Lebanon. Our data show promising results, and encourage to investigate more on these medicinal plants, especially M. barbata. Keywords: Essential oils, Antimycobacterial activity, Micromeria barbata, Eucalyptus globulus, Juniperus excelsa