M-Enterococcus Agar Base, Modified, 500 g

M-Enterococcus Agar Base, Modified was developed for the enumeration and identification of Enterococci in sanitary quality of recreational water according to USEPA (1). Cabelli et al (2) established the correlations between enterococcal densities and gastroentitis associated with swimming in recreational waters. This medium is also useful for the detection and quantitiation of Enterococci from potable, fresh, esturine, marine and shellfish growing waters (3). This medium contains gelatin peptone and yeast extract, which provide the carbonaceous and nitrogenous nutrients, minerals, vitamins and other growth factors. Sodium chloride maintains isotonic conditions of the medium beside the provision of essential ions to variety of organisms. Sodium azide, Cycloheximide and Nalidixic acid inhibit large number of bacteria and fungi and thus makes the medium selective. Esculin is hydrolyzed by bacterial enzyme to esculetin and dextrose (5). TTC is reduced by Enterococci to insoluble formazan, a red coloured complex inside the bacterial cell resulting in pink to red colored colonies. In this membrane filter procedure, two culture media namely M-Enterococcus Agar Base, Modified and Esculin Iron Agar (M1044) are used for the enumeration and identification of Enterococci where M-Enterococcus Agar, Modified serves as a selective medium while Esculin Iron Agar (M1044) confirms the identification of colonies on the basis of ability of organisms to hydrolyze esculin. Initially the membrane filter that has been used to filter the water is placed on to M-Enterococcus Agar, Modified plate and incubated at 41°C for 48 hours and after incubation transferred to the Esculin Iron Agar plate and further incubated at 41°C for 20 minutes. After incubation, count and record the colonies on those membrane filters containing 20 - 60 pink to red colonies with black or reddish-brown precipitate on the underside of the membrane. If required, magnification glass and fluorescent lamp may be used for counting the visible colonies. Following formula is used for the final calculation (4). No. of enterococcal colonies Enterococci/100ml = ----------------------------- x 100 Volume of sample filtered (ml) Storage and Shelf-life: Store below 8°C and use the freshly prepared medium. Use before expiry date on the label. References: 1. U. S. Environmental Protection Agency, 1997, EPA Method 1600: Membrane Filter test Methods for Enterococci in water, USEPA, EPA-821-R-97-004, Washington D. C. 2. Cabelli, Dufour, Levin, et al, 1979, Am. J. Public Health 69:690. 3. Greenberg A. W., Eaton A. D. and Clesceri L. S. (Eds.), 1998, Standard Methods for the Examination of Water and Waste Water, 20th ed., APHA, Washington DC. 4. Bordner, Winter and Scarpino (Eds.), 1978, EPA - 600/8-78-017 USEPA, Office of Research and Development, Environmental Monitoring and Support Laboratory Cincinnati, Ohio. 5. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore.