Estimation of low numbers of Escherichia coli bacteriophage by use of the most probable number method.

The estimation of low numbers of the Escherichia coli bacteriophage was made possible by use of the most probable number (MPN) method. This method is similar to the technique used for counting coliform bacteria. The statistical results were computed by referring to tables. The method makes it possible to record values as low as two particles per 100 ml of sample. The direct plate count and MPN method were found to be in good correlation for T2 bacteriophage and bulk T bacteriophage in samples obtained from a sewage treatment plant and from contaminated seawater.