m-FC (membrane-Fecal Coliform) Agar is a selective and differential medium used for the detection and enumeration of fecal coliforms using the membrane filtration technique at elevated temperatures. It is a standard medium for water quality testing, including drinking water, wastewater, and recreational water.
m-FC Agar (NutriSelect Plus) was originally developed by Geldreich et al. to specifically select for fecal coliforms (thermophilic coliforms) while suppressing non-fecal coliforms. The selectivity is achieved through the inclusion of bile salts (to inhibit Gram-positive organisms) and an incubation temperature of 44.5 °C. The differential system consists of aniline blue and rosolic acid. When fecal coliforms ferment lactose, they produce acid, which causes the aniline blue to turn the colonies a distinct blue color. Non-fecal coliforms and other organisms typically appear gray to cream-colored.
Advantages
- High Selectivity: Specifically optimized for the recovery of fecal coliforms from environmental samples with high background flora.
- Clear Differentiation: The deep blue color of positive colonies provides high contrast against the membrane filter for easy counting.
- Membrane Filtration Compatible: Formulated specifically for use with 0.45 µm membrane filters.
- NutriSelect® Plus Quality: Premium-grade ingredients ensure consistent batch-to-batch performance and reliable results in regulated water testing.
- Global Compliance: Follows the formulations recommended in "Standard Methods for the Examination of Water and Wastewater" (APHA).
Interpretation of Results
| Microorganism | Colony Appearance | Interpretation |
|---|---|---|
| Escherichia coli | Blue colonies | Fecal Coliform (+) |
| Klebsiella pneumoniae | Blue to blue-grey colonies | Fecal Coliform (+) |
| Enterococcus faecalis | Inhibited | Negative (-) |
| Proteus mirabilis | Grey/Cream/Colorless | Non-Fecal Coliform (-) |
Technical specifications
| Catalogue number | 96961 |
| Brand / Product Line | Sigma-Aldrich / NutriSelect® Plus |
| Typical Composition (g/L) | Tryptose (10.0); Proteose peptone (5.0); Yeast extract (3.0); NaCl (5.0); Lactose (12.5); Bile salts mixture (1.5); Aniline blue (0.1); Agar (15.0) |
| pH (at 25 °C) | 7.4 ± 0.2 |
| Preparation | 52.1 g/L + 10 mL Rosolic Acid solution |
| Storage Temperature | 15 – 25 °C |
Available packaging options
| 96961-500G | 500 g plastic bottle |
| Brand | Merck |
| Pack size | 500 g |
