What does a large zone of inhibition indicate?

A large zone of inhibition indicates that the compound being tested is effective against the bacteria. This zone represents an area around the disk where bacterial growth has been suppressed due to the action of the antimicrobial agent. The larger the zone, the more effective the compound is at inhibiting bacterial growth. This is a key concept in microbiology, particularly in the study of antimicrobial susceptibility, as it helps determine how well a particular antibiotic or antimicrobial compound can combat specific bacteria.

In this context, a small zone or no zone would suggest ineffective action or bacterial resistance, but a large zone clearly demonstrates that the bacteria are unable to grow in the presence of the compound, confirming its effectiveness.