Confirmatory Test for coliform count
**Core Concept**
The question is testing the knowledge of a confirmatory test for coliform count, which is an important aspect of water quality monitoring and public health. Coliform bacteria are a group of gram-negative, rod-shaped bacteria that are commonly found in the environment and can serve as indicators of fecal contamination.
**Why the Correct Answer is Right**
The correct answer is a confirmatory test for coliform count, specifically the **Most Probable Number (MPN) test**. The MPN test is a statistical method used to estimate the number of coliform bacteria in a water sample. It involves inoculating multiple tubes of a medium with different dilutions of the water sample and observing the growth of coliform bacteria. The MPN is then calculated based on the number of positive tubes and the dilution factor.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a confirmatory test for coliform count. **Option B:** This option is incorrect because it is a screening test for coliform bacteria, not a confirmatory test. **Option C:** This option is incorrect because it is a test for E. coli, which is a specific type of coliform bacteria, but not a confirmatory test for all coliform bacteria.
**Clinical Pearl / High-Yield Fact**
It's worth noting that the MPN test is a more sensitive and specific method for detecting coliform bacteria than the traditional multiple-tube fermentation test. Additionally, the MPN test can be used to detect low levels of coliform bacteria in water samples.
**Correct Answer: D. Most Probable Number (MPN) test**