What are the three tests performed in the multiple-tube fermentation test?

In the context of the multiple-tube fermentation test, the correct choice identifies the three essential phases of the test: presumptive, confirmed, and completed tests.

The presumptive test is the initial stage where the presence of coliform bacteria is indicated through gas production in a lactose broth, typically measured in multiple tubes. This phase helps to estimate the number of coliforms present in the water sample.

The confirmed test follows the presumptive test and verifies the presence of coliforms. This is typically achieved by inoculating selective media, such as eosin methylene blue (EMB) agar, to distinguish between different types of bacteria and confirm the identity of coliforms.

The completed test is the final stage, where isolates from the confirmed test are subjected to further testing, often involving biochemical tests to establish with certainty whether the organisms present are indeed coliforms as well as to account for their viability.

Each of these phases builds upon the last to ensure a rigorous and accurate assessment of water quality, specifically concerning the presence of coliform bacteria which are indicators of fecal contamination. Other choices do not reflect the standard methodology or terminology used in microbiological testing and would not accurately describe the series of checks involved in this important public health test