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 test the nutrient content of the medium.
• C. To monitor color changes during incubation.
• D. To assess the growth rate of inoculated cultures.

Answer: (A)

The purpose is to verify that the medium is sterile before inoculation. A sterility control plate is an uninoculated sample of the same medium incubated under the same conditions as the test plates. If no growth appears, you can trust that any organisms that grow later on inoculated plates come from the intended inoculum, not from contaminants in the medium or during preparation. If growth occurs, it signals contamination or a breach in aseptic technique, meaning the medium isn’t sterile and results from inoculations could be unreliable. This control doesn’t assess nutrient content, monitor color changes, or measure growth rate of inoculated cultures; it specifically checks that the medium itself is free of microbes prior to use.