1 The confirmatory test for coliform bacteria is and the pr

1) The confirmatory test for coliform bacteria is ___________ and the presumptive test for coliform bacteria (water experiment)?_____________. Can the membrane filter technique be used to test for coliforms. Explain you answer?

Solution

Gram negative lactose fermenters with gas producers are called coliforms.

Presumptive test - It is performed in lactose broth with an inverted small tube (Durham tube). The production of gas in the Durham\'s tube gives a presumptive indication of presence of colifirm bacteria. However, to strike out the possibility of non-coliforms, confirmatory test is performed.

Confirmatory test - It is done by inoculating the culture obtained above on eosin methylene blue (EMB) agar, which contains lactose. Coliforms ferment lactose and therefore produce dark purple colonies. Microscopic visualization of Gram negative rods confirms the presence of coliforms.

Membrane filter technique is used for total coliform, but it is not a confirmatory test, as other non-coliforms too can produce colonies of same characteristics (raised golden-green shiny colonies).