InMicro® Dehydrated: m ENDO Agar LES

Cultivate and enumerate coliform bacteria from water by membrane filtration method using InMicro® Dehydrated: m ENDO Agar LES. Endo Medium was first proposed by Endo in 1904 and allowed differentiation between lactose fermenters and non-fermenters. The m ENDO Agar LES medium is prepared according to the Lawrence Experimental Station (LES) formulation of McCarthy, Delaney, and Grasso and used for the enumeration of coliform organisms in water.

Coliforms are indicator organisms used for assessing the effectiveness of water treatment and disinfection, and for monitoring the sanitary integrity of water and wastewater. They are aerobic or facultatively anaerobic, gram-negative, non-spore forming bacteria that can ferment lactose and produce acid and gas.

Use m ENDO Agar LES for enumeration of coliforms by membrane filtration.

• Selective Medium: Sodium lauryl sulfate and sodium deoxycholate inhibit non-coliforms
• Easy to interpret: Coliforms form red colonies with metallic green sheen within 24 hrs when incubated at 35°C

This medium contains lactose as the carbohydrate source. Casein peptone and casein-meat polypeptone provide essential nutrients for the growth of bacteria. Yeast extract acts as a growth enhancer and supplies B-complex vitamins. Monopotassium and dipotassium phosphate serve as buffers whereas sodium chloride provides electrolytes and maintains osmotic equilibrium. Sodium lauryl sulfate and sodium deoxycholate are selective agents that inhibit the growth of gram-positive bacteria. Basic fuchsin is the pH indicator. Agar is the solidifying agent.

Lactose-fermentation produces acetaldehyde that reacts with the sodium sulfite and basic fuchsin to form red colonies. A metallic green sheen is observed when the organism produces aldehydes with the rapid fermentation of lactose. Non-lactose fermenting colonies are clear, colorless or light pink.

On m-Endo LES Agar, coliforms appear as red colonies with a metallic green sheen.