Antibacterial Efficacy of Cymbopogon winterianus EOs

Tryptic soy agar medium was used to culture all tested bacterial strain. A 5000 μg/mL solution of EOs was prepared in dimethyl sulfoxide (DMSO), and twofold dilution in 100 μL of cation-adjusted Mueller Hinton broth (CAMHB) (Sigma-Aldrich, St. Louis, MO, USA) was added to the top well of a 96-well microdilution plate. The prepared stock solution of EOs was then serially twofold diluted in fresh CAMHB to obtain final concentrations of 2500, 1250, 625, 312.5, 156.3, 78.1, 39.1, and 19.5 μg/mL. The freshly harvested bacteria with approximately 1.5 × 108 CFU/mL final concentration were added to each well of 96-well microdilution plates and were incubated at 37 °C for 24 h. Gentamicin (Sigma-Aldrich, St. Louis, MO, USA) and DMSO were used as positive and negative controls, respectively [56 (link)]. Seven microorganisms were used to evaluate the antibacterial activities of C. winterianus (leaves and root) EOs: Five Gram-positive bacteria, Bacillus cereus (ATCC-14579), Staphylococcus epidermidis (ATCC-12228), Propionibacterium acnes (ATCC-11827), Staphylococcus aureus (ATCC-29213), and Streptococcus pyogenes (ATCC-19615) and two Gram-negative bacteria, Serratia marcescens (ATCC-14756) and Pseudomonas aeruginosa (ATCC-27853), using the microbroth dilution technique.