Coliplate™ - Direct Pour Method

The easiest and most common means of filling the microplate, Coliplate™ with sample water is as follows:

Remove the microplate lid. Using the sample bottle in which the water sample was collected, gently pour a small stream of water onto the plate, running the stream along each row of wells so that water enters each well. Using sample bottles with smaller necks makes the pouring easier. When all wells are full and excess sample water remains on the plate, gently tap the side of the microplate to dislodge any air bubbles which may remain in the bottom of some wells. To ensure that all wells are full, view the plate in a manner where light is reflected off the surface of the wells to your eye. Top up any wells which are not full.

To remove excess water from the top of the plate, tilt the plate on a slight angle to one of the plate corners and drain off. Again, tap the plate while tilted to assist draining excess water off the top of the wells. Use a paper towel or tissue to wick away the last few drops of water at the low corner of the plate. Viewing the surface of the plate in reflected light should now reveal that all wells are full, that the surface water on each well has a slight concave shape, and that no excess water remains on the surface of the plate. If any wells remain unfilled, top up with a little more sample water and drain off excess.

Replace microplate lid and incubate at 35° C for 24 to 30 hours.

Interpretation of Results:

Place the incubated microplate on a white surface and count the number of wells which turned blue. This is the positive reaction for Total Coliforms. There will be different tones of blue depending on the strength of the bacterial colony in each well. Count ALL blue wells. Refer to the MPN table to determine the Most Probable Number for Total Coliforms in 100 mL of sample water

Place the incubated microplate on a black (dark) surface in reduced light and observe under long wavelength UV (366 nm) light. Count the number of wells that turned blue and were fluorescent under the UV light . This is the positive reaction for E. Coli. Do not count wells with fluorescence that are not also blue – they must be blue and fluorescent. Refer to the MPN table to determine the Most Probable Number for E. Coli in 100 mL of sample water.