M-LAURYL SULPHATE BROTH

The membrane filter technique is used to test relatively large volumes of samples. It is extremely useful in monitoring drinking water and a variety of natural waters. The earlier medium used to detect coliforms in water employed bile salts as the selective agent. This was replaced with Teepol by Burman. The effectiveness of teepol was demonstrated earlier. M-Lauryl Sulphate Broth is similar to this medium, the only difference being the use of sodium lauryl sulphate as the inhibitory agent instead of teepol. M-Lauryl Sulphate Broth is recommended for enumeration of Escherichia coli and coliforms using membrane filtration technique.
An absorbent pad is saturated with M-Lauryl Sulphate Broth. The filter, through which the water sample is passed, is aseptically placed on this saturated absorbent pad, with face upwards. Burman recommended the following incubation temperatures and durations. Unchlorinated waters:
Coliform organisms: 4 hours at 30?C followed by 14 hours at 35?C
Escherichia coli: 4 hours at 30?C followed by 14 hours at 44?C
Non-chlorinated organisms benefit from 4 hours? incubation at 30?C but chlorinated organisms require 6 hours? incubation at 25?C. After incubation, yellow colonies are formed which should be confirmed further.

for enumeration of Escherichia coli in water using membrane ?ltration technique.