Antimicrobial activity based on disc diffusion test

Antimicrobial activity of each extract (NG or AG) was tested against Salmonella enteritidis, Staphylococcus aureus, Escherichia coli, Bacillus cereus, and Listeria monocytogenes using agar diffusion technique [17]. Bacterial colonies were suspended in normal saline to obtain approximate concentrations (10⁶–10⁷ CFU/mL). Filter paper discs (Whatman, 6 mm in diameter) were dipped in each sample (50 μL) and dried for 3 h. All plates were incubated at 37 °C for 24 h. The diameter of the resulting zone of inhibition was measured in mm. Penicillin was used as positive control while distilled water was used as negative control.