I am trying to screen antibiotic disc using disc diffusion method so I have prepared the inoculum of P. acnes as the following
The 72 h culture of the bacteria was dissolved in .85% saline and the suspension was adjusted to 0.5 McFarland standard turbidity. A sterilized cotton swab was
dipped in the P. acnes inoculum and agar plate was streaked 4 times and I also subculture some plate.
I repeated the experiment two times, but still no lawn form. I only got a result for my subculture plate