Antimicrobial activity of blended essential oils of Allium sativum, Syzygium aromaticum and Cymbopogon citratus against upper respiratory tract pathogens

The present study aimed to evaluate the antibacterial potential of commercial Syzygium aromaticum, Cymbopogon citratus and Allium sativum essential oils both individually and in combination for a gargle formulation. First, GC/MS analyses were used to verify the chemical composition of the tested essential oils. For the antibacterial activity evaluation, in vitro broth microdilution, as well as the checkerboard method, and the inhibition zones of the formulated gargles were evaluated using the disc diffusion assay. The main components were verified as eugenol (78.4%) in S. aromaticum; methyl thiirane (52.3%) in A. sativum; followed by geranial (45.4%) in C. citratus, respectively. Synergistic effects were observed for combinations with S. aromaticum and C. citratus (FICI = 0.375), also for S. aromaticum and A. sativum (FICI = 0.265and FICI = 0.375). The essential oil combinations showed in vitro synergistic and additive interactions, and the formulated gargles showed inhibition zones. These initial findings highlight the potential of essential oil combinations as natural antibacterial agents.