Disc diffusion method. The antimicrobial activity screening
of Plai oil was carried out using disc diffusion method
described in the Manual of Clinical Microbiology
(Woods and Washington, 1995) with slight modifications.
Several concentrations of Plai oil were prepared
by serial dilution in propylene glycol (PG) as the
solvent: 50, 25, 12.5 and 6.25 vol %. Each prepared
inoculum (20 μL) was added to molten SDA at 45–
50 °C, mixed, poured over the surface of a SDA plate
and left to solidify. A sterile paper disc (6 mm in diameter)
was impregnated with the test preparation of
Plai oil and the disc was placed on the agar (one disc
per plate). Plates were then incubated at 30 °C for
5 days for filamentous fungi and 37 °C for 3 days for
yeasts. Similar procedures were used for antibacterial