disc diffusion

Disc diffusion is a laboratory method used to test how well antibiotics can stop bacteria from growing. A small disc containing an antibiotic is placed on the surface of a gel-like substance called agar that’s been inoculated with bacteria. If the antibiotic is effective, a clear zone will form around the disc where bacteria do not grow. The size of this zone indicates the antibiotic’s effectiveness: larger zones mean stronger activity, smaller zones suggest weaker activity, and no zone means resistance. This test helps determine the most effective antibiotic to treat an infection.