Evaluation of a new most-probable-number (MPN) dilution plate method for the enumeration of Escherichia coli in water samples.

The purpose of this study was to evaluate the most-probable-number dilution plate (MPN plate) method developed for the enumeration of Escherichia coil in water samples. Sterilized water was inoculated with E. coli ATCC 11775 to give between 2-1600 MPN/100 ml. The MPN was determined for both the MPN plate and 5-tube methods from the MPN table. The average of the natural logarithm (In) MPN with standard deviations in 95 samples was 4.26 +/- 1.48 by the 5-tube-method and 4.18 +/- 1.45 by the MPN plate method. The correlation coefficient was 0.96. These results were not significantly different according to the paired t-test (p > 0.05).