Spray the bench you are working on with disinfectant then wipe dry with paper towels.
On the bottom of the agar plate (not the lid) mark with a wax pencil / permanent marker:
3 segments
a dot in the middle of each segment
your initials, date, name of bacteria as seen below
Wash your hands with antibacterial handwash.
Place the different antiseptics onto different filter paper discs.
Lift the lid of the agar plate at an angle carefully and use forceps to place each filter paper disc onto the dots. Note down the antiseptic applied to each zone.
Tape the lid onto the agar plate securely, but loosely enough that oxygen can still reach the bacteria.
Place the agar plate in the incubator at 25°C for 48 hours.
Measure the diameter of the clear zones after 48 hours using a ruler. Take a second measurement at 90 degrees from your first measurement and take a mean for the diameter. Do not remove the lid when taking measurements.
Record the results in a table as seen below. The area of the clear zones can be calculated using the formula πr².
Method
Clean the workbench with disinfectant
Sterilise inoculating loop
Open sterile agar gel petri dish near bunsen burner
Use loop to evenly spread chosen bacteria
Place sterile filter paper discs containing antibiotic onto place