Chemical composition and antibacterial activity of seven uncommon essential oils

Seven uncommon types of essential oils obtained from Pinus nigra, Hyssopus officinalis, Sison amomum, Smyrnium olusatrum, Helosciadium nodiflorum, Pelargonium graveolens and Vepris macrophylla were tested against a panel of thirty bacterial strains that cause serious infectious diseases. Among these bacterial species, the most dangerous for human health were five documented multi-drug-resistant strains belonging to the Acinetobacter and Klebsiella genera and derived from clinical isolation. The chemical composition of essential oils was achieved by GC-MS analysis, whereas the antibacterial efficacy was evaluated by the microdilution technique according to CLSI document M7-A9. The Vepris macrophylla essential oil, which contains geranial (33.2%), neral (23.1%) and citronellol (14.5%), exhibited the strongest inhibition against the multi-resistant strains A. baumannii, K. pneumoniae and S. aureus, with MIC values of 4.1, 2.05 and 4.1 mg/ml, respectively.