m-Endo Agar LES (NutriSelect® Plus) is often used in a two-step procedure to reduce the stress on bacterial cells and improve recovery. The medium contains basic fuchsin and sodium sulfite, which act as selective agents by inhibiting the growth of Gram-positive bacteria. Differentiation is based on lactose fermentation. When coliforms ferment lactose, the released acetaldehyde reacts with the sodium sulfite and basic fuchsin to form red colonies with a distinctive metallic green sheen (fuchsin luster). As part of the NutriSelect® Plus line, this medium ensures high sensitivity and batch-to-batch consistency for regulated water testing laboratories.
Advantages
- Superior Differentiation: The characteristic metallic green sheen allows for rapid and accurate visual identification of total coliforms.
- High Recovery: The LES formulation is optimized to recover injured or stressed bacteria in drinking water and treated effluent.
- NutriSelect® Plus Quality: Manufactured with high-purity raw materials to ensure a stable background color and intense colony sheen.
- Standard Compliance: Recommended by the APHA in "Standard Methods for the Examination of Water and Wastewater" for water testing.
- 24-Hour Results: Enables rapid enumeration, facilitating quick decision-making in water quality control.
Interpretation of Results
| Microorganism |
Colony Appearance |
Interpretation |
| Escherichia coli |
Red with metallic green sheen |
Total Coliform (+) |
| Enterobacter aerogenes |
Red with metallic green sheen |
Total Coliform (+) |
| Salmonella typhimurium |
Colorless to pale pink |
Non-coliform (-) |
| Staphylococcus aureus |
Inhibited |
Negative (-) |
Technical specifications
| Catalogue number |
85766 |
| Brand / Product Line |
Sigma-Aldrich / NutriSelect® Plus |
| Typical Composition (g/L) |
Casein peptone (3.7); Meat peptone (3.7); Gelatin peptone (1.2); Yeast extract (1.2); Lactose (9.4); K2HPO4 (3.3); KH2PO4 (1.0); NaCl (3.7); Sodium sulfite (1.6); Basic fuchsin (0.8); Agar (15.0) |
| pH (at 25 °C) |
7.2 ± 0.2 |
| Preparation |
51.05 g/L + 20 mL Ethanol |
| Storage Temperature |
15 – 25 °C |
Available packaging options
| 85766-500G |
500 g plastic bottle |
