Index >> Water Pollution Microbiology >>Multiple Tube Test

Multiple Tube Test - Multiple tube method is also known as most probable number method as it is based on the statistical values of the results obtained.
This method detects and estimates various groups of microorganisms in water samples.
This method actually involves three stages: presumptive test, confirmative test and completed test.
In this method, measured volumes of water or of one or more dilutions are added to a series of tubes containing suitable liquid differential medium.

To confirm that the positive reactions in the presumptive test are due to the growth of specific indicator organisms, they are subcultured to tubes of confirmatory media.
Positive reactions in the confirmatory tests confirm the presence of indicator organisms.
Completed test, which involves biochemical tests for identification, yields further information about the type of organisms present.
The presumptive and confirmed counts are calculated by referring to the probability tables.