What is the purpose of a sterility control plate in media preparation?

• A. To verify that the medium remains sterile prior to inoculation.
• B. To measure nutrient content.
• C. To test the effect of antibiotics on growth.
• D. To determine the pH of the medium.

Answer: (A)

Sterility control plates are used to confirm that the medium is free from microorganisms after sterilization and before any inoculation. By incubating a plate that contains no inoculated sample (or a purposely sterile portion of the medium handled under sterile technique), you can check whether any contaminants were introduced during preparation or handling. If no growth appears after incubation, the batch is considered sterile and suitable for experiments. If colonies do appear, it indicates contamination and the batch should not be used, prompting review of sterilization and aseptic procedures. This check specifically ensures that results from later inoculations reflect only the intended organisms, not unintended contaminants. It’s not about measuring nutrient content, testing antibiotic effects, or determining pH.