Required practical: antiseptics/antibiotics on bacterial growth

Know the practical language

Get these terms clear before following the method.

From culture to measurement

Follow the practical in order and notice where contamination and safety are controlled.

1. 1Start asepticallySterilised media and dishes and a sterilised flamed inoculating loop reduce contamination of the culture.+
2. 2Build an even lawnSpreading the bacteria evenly across the agar creates an even layer of bacterial growth.
3. 3Add the treatmentsPlace paper discs soaked in different antiseptics or antibiotics onto the bacterial lawn.+
4. 4Secure and incubateSecure the lid with tape rather than sealing it completely, then incubate at a maximum of 25 °C.+
5. 5Measure the clear zonesMeasure the zones of inhibition around treated discs to compare how strongly bacterial growth was inhibited.

Measure a clear zone

Which treatment inhibited more?

Assume both treatments were tested under the same controlled conditions.

Treatment A produces a clear zone with radius 6 mm and Treatment B produces one with radius 3 mm. Which treatment inhibited bacterial growth more?