2.3. Antagonism assay

PDA agar supplemented with 1% (w/v) yeast extracts (Merck, Germany) medium was used for the antagonism assay. S. aureus ATCC® 29213™, Methicilin-resistant S. aureus ATCC® 43300™, E. coli ATCC® 25922™, and Enteropathogenic E. coli K11 were of collections of the Hospital of Universitas Sumatera Utara, Medan, Indonesia. The antagonism assay of endophytic fungi was performed by dual culture assay (Balouiri et al. 2016). Direct bacterial suspensions were made by swabbing colonies and dipping them in a sterile saline solution (0.95% NaCl) to obtain OD₆₀₀: 0.5 ≈ 1.2 × 10⁸ CFU/mL. One mL of cell suspension was inoculated into 15 mL molten PDA (45 °C), and then plated to get microbial lawns. Three agar plugs of fungal mycelium were placed over the medium. The plates were incubated for 2 days in ambient temperature. Clear zones indicating inhibitory activities around mycelial plugs indicating antagonism were measured in millimetre unit (mm) using the standard caliper.