Membrane Lactose Glucuronide Agar (mLGA) is a medium for the detection and identification of E. coli and coliforms from water samples and is not intended for use in the diagnosis of disease or other conditions in humans. Traditionally, membrane Lauryl Sulphate Broth (mLSB) has been used as the standard media for isolating coliforms (including E. coli) from water potentially contaminated with sewage. Harlequin membrane Lactose Glucuronide Agar (mLGA) is a modification of mLSB aimed at reducing costs by reducing the number of filters used per test sample and aiding in the recovery and identification of coliforms and E. coli. The medium has been modified from the mLSB formulation by the incorporation of X-glucuronide (BCIG), sodium pyruvate and agar. X-glucuronide is a chromogenic substrate which detects the β-glucuronidase enzyme – highly specific for E. coli* – and allows for the presumptive isolation of E. coli. Sodium pyruvate aids the recovery of chlorine stressed organisms and agar is incorporated to remove the need for absorbent pads. This medium is recommended for the enumeration of coliform bacteria and E. coli by a single membrane filtration technique in The Microbiology of Drinking Water 2009 (previously Report 71). *96-97% of E. coli strains positive. A notable exception is E. coli O157:H7.