Esculin Iron Agar, 500 g

Enterococci are indicators of the sanitary quality of recreational waters, since they occur in faeces of humans and warmblooded animals (1). Detection and quantitation of Enterococci is necessary because gastroenteritis is associated with swimming in recreational water, which is dependant of enterococcal densities (2). Esculin Iron Agar is used in conjunction with MEnterococcus Agar, Modified, (M1048) for verification of enterococcal colonies in fresh and marine recreational water, as recommended by APHA (3). Esculin in the medium is hydrolyzed by Enterococci to form esculetin and dextrose. Esculetin reacts with the iron salt (ferric ammonium citrate) and produces a dark brown to black complex, which appears around the colonies. In the membrane filtration technique, two media, namely M-Enterococcus Agar, Modified (M1048) and Esculin Iron Agar (M1044) are used in conjunction, where the former serves as a selective medium while the later confirms the identification of colonies on the basis of its ability to hydrolyze esculin. The membrane filter used to filter the test water sample is aseptically placed on M-Enterococcus Agar, Modified (M1048) and incubated at 40-42°C for 48 hours. After incubation the membrane is aseptically transferred to Esculin Iron Agar (M1044) plate and incubated at 40-42°C for 20 minutes. After incubation count and record the number of pink to red colonies with black or reddish brown precipitate on the underside of the membrane.If required, magnifying glass or fluorescent lamp may be used for counting the visible colonies. Following formula is used for the final calculation (3). Storage and Shelf-life: Store below 30°C in tightly closed container and the prepared medium at 2 - 8°C. Use before expiry date on the label. References: 1. U. S. Environmental Protection Agency, 1997, EPA Method 1600: Membrane Filter Test Method for Enterococci in Water,EPA-821-R-97-004, Washington, D.C. 2. Cabelli et al, 1979, Am. J. Public Health, 69:690. 3. Eaton A. D., Clesceri L. S. and Greenberg A. E., (Ed.), 1998, Standard Methods for the Examination of Water and Wastewater, 20th Ed., American Public Health Association, Washington, D.C.