Antibiotic Testing • Zone of Inhibition

Measure Zones of Inhibition to Compare Antibiotic Effectiveness

Drop antibiotic disks onto a bacterial lawn and watch inhibition zones appear. Use the on-plate ruler to estimate zone diameters, mirroring the Kirby-Bauer test taught in microbiology labs.

Green lawn = susceptible bacteria

Colored disks = antibiotics

Larger clear zones ≈ stronger or more effective antibiotic (under these conditions).

Bacterial lawn (test organism)

Disk A (moderate)

Disk B (weak)

Disk C (strong)

Clear zone = growth inhibited

Click to drop antibiotic disks and measure zones

Mode: Waiting: seed the plate

Start by seeding the plate with a uniform bacterial lawn. Choose an antibiotic (A, B, or C), then click on the plate to drop disks. Clear zones expand around each disk; use the ruler to estimate which antibiotic produces the largest inhibition zone.

Approximate zone diameters

Disk A

–

mm (simulated)

Disk B

–

mm (simulated)

Disk C

–

mm (simulated)

Largest zone

–

Most effective here

How to use this simulation

Click “Seed bacterial lawn”.
Select A, B, or C, then click on the plate to place disks.
Watch clear halos form and stabilize around each disk.
Toggle the ruler to see a scale; compare halo diameter in “mm”.

What this teaches

Zones of inhibition show where bacteria cannot grow near an antibiotic.
Larger zones usually mean more effective drug or higher susceptibility.
This mirrors Kirby-Bauer disk diffusion tests used in clinical labs.
Real labs use standardized tables; here you build intuition about “bigger clear zone = stronger effect” for a given organism.