How big is the clear ring? That depends on the treatment. Disks soaked in acne medications go onto agar plates covered with P. acnes bacteria, and after incubation you measure the ring where bacteria could not grow. Comparing ring sizes reveals which treatments are strongest — prescription antibiotics produced the largest ones, but oregano oil turned up as a surprise third-place finisher.

The Kirby-Bauer disk diffusion test checks which germ-killing drugs work best by measuring how far they stop germs from growing on a plate. This experiment tests that directly against the bacterium that causes acne. Disks soaked in prescription antibiotics, over-the-counter medications, and plant extracts like oregano oil and tea tree oil go onto agar plates covered with Propionibacterium acnes. After incubation, the inhibition zone — the clear ring where bacteria cannot grow — around each disk reveals which treatment fights the bacterium most effectively. Prescription antibiotics produced the largest zones, though oregano oil ranked third overall, an unexpected result.

Incubation supplies the warmth, moisture, and air that let organisms grow to a visible size. Disks soaked in acne treatments are placed on agar plates seeded with Propionibacterium acnes. After incubation, bacteria have multiplied everywhere except around effective treatments. Those clear rings, called inhibition zones, mark where the medication stopped bacterial growth during the controlled incubation period.

Antibiotics kill harmful germs or stop them from growing, and their strength can be measured by how wide a clear ring forms around a treated disk. This project puts that to the test, comparing prescription antibiotics, over-the-counter acne creams, and plant extracts like oregano oil and tea tree oil against Propionibacterium acnes. Disks soaked in each treatment go onto agar plates with the bacteria, and after incubation you measure the inhibition zone — the clear ring where bacteria cannot grow. The prescription antibiotics produced the largest zones overall, though oregano oil ranked third, an unexpected result among the store-bought and plant-based options.

Propionibacterium acnes lives on skin and drives acne — but not all treatments stop it equally. In this project, prescription antibiotics, over-the-counter medications, and plant extracts are tested side by side against it. Disks soaked in each treatment go onto agar plates with the bacterium, and after incubation you measure the inhibition zone: the clear ring where bacteria cannot grow. The prescription antibiotics produced the largest zones. One surprise: oregano oil ranked third overall, outperforming several store-bought treatments.