ANTIBACTERIAL ACTIVITY OF VETIVER, CITRONELLA, AND EAST INDIAN LEMONGRASS ESSENTIAL OILS AGAINST BACILLUS SUBTILIS: A PRELIMINARY DISK-DIFFUSION STUDY
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Antimicrobial resistance has increased interest in plant-derived antibacterial agents. This study aimed to evaluate and descriptively compare the antibacterial activities of Vetiver (Chrysopogon zizanioides), Citronella (Cymbopogon nardus), and East Indian lemongrass (Cymbopogon flexuosus) essential oils against Bacillus subtilis. Preliminary antibacterial screening was conducted using an adapted disk-diffusion method. Gentamicin and sterile distilled water served as positive and negative controls, respectively. Inhibition-zone diameters were measured after 24 h and reported as mean ± standard deviation from three independent biological replicates. All three oils produced measurable inhibition zones. Vetiver oil had the largest observed mean zone among the oils (17.33 ± 1.53 mm), followed by East Indian lemongrass oil (15.00 ± 1.00 mm) and Citronella oil (13.67 ± 1.53 mm). Gentamicin produced a mean zone of 24.33 ± 0.58 mm. Sterile distilled water produced no inhibition beyond the 6-mm disk. Because no inferential statistical analysis was performed, treatment differences should be interpreted descriptively rather than as statistically significant. The findings show that the three oils inhibited B. subtilis under the tested conditions. Further studies should chemically characterize the tested oil batches, reproduce the screening findings, and evaluate additional Gram-positive and Gram-negative bacterial species.
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