Which biochemical test differentiates lactose fermenters from non-lactose fermenters in Enterobacteriaceae?

Which biochemical test differentiates lactose fermenters from non-lactose fermenters in Enterobacteriaceae?

• A. Indole test
• B. MacConkey agar test
• C. Triple sugar iron (TSI) test
• D. API test

Answer: (B)

The MacConkey agar test is a selective and differential growth medium that is specifically designed to distinguish between lactose fermenters and non-lactose fermenters within the Enterobacteriaceae family. This test works on the principle that lactose fermenters, such as Escherichia coli, will ferment lactose present in the medium, producing acid as a byproduct. The production of acid leads to a drop in pH, which causes a color change in the pH indicator included in the agar, typically changing from light pink to bright pink. Non-lactose fermenters, on the other hand, do not produce acid from lactose fermentation, so they either grow without changing the color of the medium or may produce colonies that are colorless. This clear differentiation based on color and colony morphology is what makes the MacConkey agar test an effective tool for identifying lactose fermenters. While the indole test, triple sugar iron (TSI) test, and API test are all valuable biochemical tests for Enterobacteriaceae, none of them specifically function to differentiate lactose fermenters from non-lactose fermenters in the way that MacConkey agar does. Indole tests determine the presence of indole production, TSI tests assess glucose, lactose,

The MacConkey agar test is a selective and differential growth medium that is specifically designed to distinguish between lactose fermenters and non-lactose fermenters within the Enterobacteriaceae family. This test works on the principle that lactose fermenters, such as Escherichia coli, will ferment lactose present in the medium, producing acid as a byproduct. The production of acid leads to a drop in pH, which causes a color change in the pH indicator included in the agar, typically changing from light pink to bright pink.

Non-lactose fermenters, on the other hand, do not produce acid from lactose fermentation, so they either grow without changing the color of the medium or may produce colonies that are colorless. This clear differentiation based on color and colony morphology is what makes the MacConkey agar test an effective tool for identifying lactose fermenters.

While the indole test, triple sugar iron (TSI) test, and API test are all valuable biochemical tests for Enterobacteriaceae, none of them specifically function to differentiate lactose fermenters from non-lactose fermenters in the way that MacConkey agar does. Indole tests determine the presence of indole production, TSI tests assess glucose, lactose,