Final answer:
The in-use test is employed in clinical settings to assess the effectiveness of a disinfectant by checking for microbial contamination in the used solution. If there is growth of five or more microbial colonies on the test plates, the disinfectant is considered contaminated and potentially ineffective.
Step-by-step explanation:
In clinical settings, surface disinfectants are used to control microbial growth and are essential in maintaining a safe environment to prevent disease transmission. To ensure the effectiveness of disinfectants, specific tests are conducted. The in-use test is designed to determine whether a disinfectant solution actively used in a clinical setting is microbially contaminated. This involves taking a sample of the used disinfectant, diluting it, and applying it onto agar plates to check for microbial growth. A growth of five or more colonies on either plate indicates that the disinfectant solution is contaminated, suggesting it may not be effective at its intended purpose. Aside from in-use tests, the use-dilution test is another method to measure disinfectant effectiveness on inanimate surfaces, whereby a cylinder coated with the target microorganism is exposed to the disinfectant and then monitored for bacterial survival in a fresh medium.