Characterizing the Antibacterial Properties and Transcriptional Alterations Induced by Lemongrass oil in Staphylococcus aureus


Collin J. Christensen and Kelsi L. Anderson​

Volume 3
Fall 2016 / Winter 2017

Essential oils have risen in popularity as “all natural” alternatives used to treat a myriad of conditions. To begin to elucidate the antibacterial properties of essential oils, we tested the effectiveness of lemongrass oil (LGO), tea tree oil (TTO), and willow bark extract (WBE) against Staphylococcus aureus growth. To do so, a Methicillin-Resistant strain of Staphylococcus aureus (USA300) was exposed to each oil using disk diffusion assays. Of the oils, LGO had the greatest zone of inhibition. The Minimum Inhibitory Concentration (MIC) of both LGO and citral (the primary chemical component of LGO) was determined in macro-broth cultures; exposure to increased concentrations of each resulted in dramatic cell death as determined by cell growth assays. To begin to determine the molecular mechanisms underlying the observed antibacterial effects, we exposed cells to a sub-inhibitory concentration of citral and hybridized the RNA to Affymetrix GeneChips®. Transcripts differentially affected in citral- versus mock-treated cells represent virulence factors, hypothetical proteins, and intergenic regions. Taken together, these results demonstrate that LGO exhibits antibacterial properties against a highly pathogenic bacterial species that is exceedingly resistant to the currently available antibiotics.