Which of the following is NOT a component of the API test system?

The API test system is designed for the identification of microorganisms, particularly bacteria, through biochemical testing. It consists of various components specifically aimed at evaluating metabolic activity, enzyme production, and other biochemical properties.

Microtiter plates are commonly used in various laboratory assays, providing a format for multiple parallel tests. In the case of the API test system, they allow for the simultaneous evaluation of several biochemical reactions.

Biochemical substrates are essential components of the API test system. They are the specific substances that bacteria metabolize, and the reactions that occur with these substrates help identify the organism based on characteristic metabolic pathways.

Reagents for colorimetric changes are also crucial in the API system. These reagents react with the products of bacterial metabolism to produce color changes, allowing for visual interpretation of results.

In contrast, antibiotic sensitivity discs are not part of the API test system. They are used in separate assays designed to assess the susceptibility of bacteria to specific antibiotics, which is a different purpose than that of the API identification system. This distinction clarifies why antibiotic sensitivity discs do not belong in the list of components associated with the API test system.