In the MPN test,at which stage would the first identification of lactose fermenting organisms occur?

Question

Quizplus · Accepted Answer

The first identification of lactose fermenting organisms occurs in the presumptive stage of the MPN test, where the presence of acid and gas production is detected as an indicator of lactose fermentation. This stage is used to estimate the most probable number of coliform bacteria in the sample. The confirmed stage is used to confirm the presence of coliforms by testing for their ability to produce gas from lactose, while the completed stage is used to confirm the presence of E. coli by testing for the presence of beta-glucuronidase. The conclusive stage, also known as the typical coliform or Escherichia coli test, is used to confirm the presence of E. coli by testing for the ability to grow on a selective medium and produce beta-glucuronidase. Therefore, only the presumptive stage would permit the identification of lactose fermenting organisms.

In the MPN Test,at Which Stage Would the First Identification