In the Testing of Water for Coliforms,the Presumptive Test Involves

Question

In the testing of water for coliforms,the presumptive test involves detection of
A)gas production in a lactose broth medium.
B)sheen production on a selective medium.
C)a gram-negative nonspore-forming rod.
D)All of these choices are correct.

Accepted Answer

The presumptive test for coliforms involves the detection of gas production in a lactose broth medium by using an inverted Durham tube. If gas is produced, it indicates the presence of coliforms, which are lactose-fermenting, gram-negative, non-spore-forming rods. Sheen production on a selective medium (B) is used to detect the presence of fecal coliforms, which are a subgroup of coliforms. Choice D is incorrect because a gram-negative nonspore-forming rod (C) is a characteristic of coliforms but not specific for their detection.