2.6.1. Antibacterial Disk Diffusion Assay

The in-vitro antibacterial activities of *C. pentandra*/Ag-NPs was evaluated qualitatively using the Kirby-Bauer technique [19], which conformed to the recommended standards of Clinical and Laboratory Standards Institute (CLSI). Two Gram-positive bacteria (S. *aureus* and *E. faecalis*), including two Gram-negative bacteria (*E.coli* and *P. vulgaris*) were used in this study. Gentamicin antibiotic disk standard (10 μg), plain disk and *E. spiralis* extract were used as positive and negative controls, respectively. All the glassware, apparatus and culture media were sterilized in an autoclave at 0.1 MPa and 121 ◦C for 15 min. The agar plate was prepared by solidifying 20 mL of liquid Mueller Hinton agar (MHA) into disposable sterilized petri dishes. The inoculum was prepared by subculturing 100 μL of stock culture bacteria into new sterile Mueller Hinton broth (MHB). The bacterial suspension was incubated overnight at 37 ◦C in the incubator before adjusted their optical density OD600 to 0.10 absorbance (1.5 <sup>×</sup> <sup>10</sup><sup>6</sup> CFU/mL) using UV spectrophotometer (Secomam, Champigny sur Marne, France). The different masses of fibers (1, 2 and 4 mg) with the diameter around ~3 mm were applied directly on the MHA plate streaked with adjusted inoculum by following the method by Ravindra et al. [11]. The experiment was carried out in triplicate and the diameter of the inhibition zone was measured after 24 h of incubation at 37 ◦C. The data were reported in the mean ± standard error of the mean (S.E.) of three experiments.
