Multiple Tube Test Procedure - Most probable number test can be done either with three dilutions or five dilutions of the sample. The dilutions used must be in consecutive order. For example, 10ml, 1 ml and 0.1ml or 1 ml, 0.1ml and 0.01 ml and so on for three dilutions procedure and 100ml, 10ml, 1ml, 0.1ml and 0.01ml or 10ml, 1ml, 0.0lml and 0.001ml for five dilutions technique. Each dilution requires five media tubes, thus the sample is inoculated in five replicas of each dilution.
In the presumptive test, the samples are inoculated, each in 10ml of the corresponding broth. If the sample volume is 10ml or more, then the medium used should be of double strength. After 24-48 hours of incubation at the specified temperature the results are noted based on acid production and/or gas production in the tubes.
