Antimicrobial Screening of E. beddomei Essential Oil

The antimicrobial activity of E. beddomei essential oil was screened by the disc diffusion method according to Lu et al.^{40 (link)} with some modifications. All bacterial pathogens were cultured in Mueller Hinton agar while C. albicans was cultured in potato dextrose agar (PDA). All bacterial and fungal pathogens were then sub-cultured in nutrient broth and potato dextrose broth (PDB), respectively. The bacterial pathogens were incubated at 37 °C for 24 h while the fungus pathogen was incubated at 28 °C for 48 h. The active bacterial pathogens were prepared in a nutrient broth until it matched the 0.5 McFarlane standard (1 × 10⁸ colony-forming unit/mL). The bacterial pathogens were spread out on the dried surface of the nutrient agar plates. The serialized 6 mm diameter paper discs (Whatman, USA) were impregnated with 30 µL of E. beddomei essential oil solution (10 µg/mL) preparing in 10% DMSO. The paper discs were then placed on the nutrient agar plate. These plates were incubated at 37 °C for 24 h. The fungus plates were incubated at 28 °C for 48 h. The diameter of the zone inhibition was determined. Chloramphenicol (10 µg/mL) and 10% DMSO were used as the positive and negative controls, respectively. Each experiment was performed in replicates.