OBSERVATIONS ON THE USE OF A MEDIUM DETECTING BETA-GLUCURONIDASE ACTIVITY AND LACTOSE FERMENTATION FOR THE SIMULTANEOUS DETECTION OF ESCHERICHIA-COLI AND COLIFORMS

A Study Of the use of a recently described single membrane medium for the simultaneous enumeration of Escherichia coli and coliforms has sho wn similar E. coli confirmation rates (92%) for both membrane lauryl s ulphate broth (MLSB) and membrane lactose glucuronide agar (mLGA). Of the presumptive E. coli examined, a higher proportion of those examine d from MLSB subsequently produced acid and gas from lactose peptone wa ter and indole from tryptophan than on mLGA. These results differ in s ome respects from those presented in the original paper and may theref ore be of interest to those workers involved in the detection of E. co li in water. Further investigation showed that mLGA which has been sto red under aerobic conditions was less efficient than freshly-prepared medium in recovering coliforms and that the size of the colonies obtai ned on stored medium was sometimes much smaller than those found on fr eshly-prepared medium.