Illustrative image only. Actual product may vary.m-Endo Agar LES
Also known as：m-Endo LES · m-Endo Agar (Lawrence Experimental Station) · Membrane Endo Agar LES · m Endo LES Agar · Endo Agar LES · Lawrence Experimental Station Endo Agar
For the enumeration of total coliforms in water by the membrane filtration technique.
- Category
- Dehydrated Culture Media
- Dissolve per litre
- 51.05 g
- Pack sizes
- 500 g · 5 kg · 25 kg
- Standard methods
- APHA 9222B
Data updated：2026-11-06
Brand cross-reference：BD Difco m Endo Agar LES · Oxoid m-Endo Agar LES · Merck Endo Agar（APHA 9222B） Brand cross-reference
- Allergens
- Soy, Milk
Overview
m-Endo Agar LES is the membrane filtration medium for coliforms in drinking water and source water: lactose-fermenting colonies develop a red colour with a green metallic sheen through the basic fuchsin and sodium sulfite reaction, and the LES formulation (Lawrence Experimental Station) includes a short resuscitation on LST broth before the membrane is transferred, improving recovery of injured cells. Specified by APHA Standard Methods 9222B and a staple for tap water, bottled water and pool water testing. Contains dye; heat to dissolve without autoclaving.
Principle
m-Endo Agar LES was developed at the Lawrence Experimental Station for the enumeration of coliforms in water by membrane filtration.¹ Yeast extract, pancreatic digest of casein, thiopeptone, and tryptose supply nitrogen, amino acids, vitamins, and growth factors, and lactose serves as the fermentable carbohydrate. The phosphate buffer maintains the pH, and sodium chloride the osmotic equilibrium. Sodium deoxycholate, sodium lauryl sulphate, and ethanol inhibit Gram-positive bacteria and other non-coliform organisms. In the prepared medium, sodium sulphite decolourises basic fuchsin. Coliforms ferment lactose to produce acetaldehyde, which reacts with the sulphite and releases the fuchsin, so that colonies appear pink to dark red with a characteristic golden-green metallic sheen. Colonies with this sheen are counted as presumptive coliforms and verified as specified in the standard method.²
How selective media fit into the testing workflow
Pathogen testing normally runs in three stages: a pre-enrichment medium such as Buffered Peptone Water repairs injured cells and raises numbers, a selective enrichment then suppresses competing flora, and finally a selective differential agar isolates the target colonies. Selective agents are typically bile salts, dyes, or antibiotics; differential agents make target colonies develop a characteristic colour or morphology. Choose the combination specified by the method you follow.
Directions
Suspend 51.05 g of powder in 1 L of purified water containing 20 mL of 95% ethanol. Heat with continuous stirring and bring to the boil for 1 minute. DO NOT AUTOCLAVE. Cool to 45-50°C and dispense into 50-60 mm Petri plates, protecting the medium from light. Test the finished medium for performance using stable, standard control cultures.
Cultural response
| Test organism | ATCC | Growth |
|---|---|---|
| Escherichia coli | 25922 | good-luxuriant |
| Klebsiella aerogenes | 13048 | good-luxuriant |
| Salmonella enterica ser. Typhimurium | 14028 | good |
| Enterococcus faecalis | 29212 | inhibited |
Product highlights
- Manufactured to the standard formulation, 51.05 g per litre
- Performance verified against standard control strains before release (Escherichia coli, Klebsiella aerogenes, Salmonella enterica ser. Typhimurium, Enterococcus faecalis)
- Available in 500 g / 5 kg / 25 kg, from laboratory to industrial scale
- COA, specification sheet, and technical data sheet available; samples on request
- Manufactured in Taiwan with reliable supply
Frequently asked questions
01Can selective media be autoclaved?
Not always. Some media containing dyes or selective inhibitors lose their selectivity if overheated and should only be heated until fully dissolved, without autoclaving. Follow the preparation instructions for this product, and contact us if you are unsure.
02How much powder per litre?
Use 51.05 g per litre of deionised water; preparation and sterilisation conditions are given on the specification sheet.
03Which organisms is it suitable for?
Coliforms, Gram-negative, E. coli, Escherichia coli, Klebsiella aerogenes, Salmonella enterica ser. Typhimurium, Enterococcus faecalis. See the cultural response table and the specification sheet.
04What are the equivalent brand products and standard methods?
Cross-reference: BD Difco m Endo Agar LES, Oxoid m-Endo Agar LES, Merck Endo Agar. Standard methods: APHA 9222B. Formulations may differ slightly between makers; refer to the specification sheet.
05How is this product prepared?
Suspend 51.05 g of powder in 1 L of purified water containing 20 mL of 95% ethanol. Heat with continuous stirring and bring to the boil for 1 minute. DO NOT AUTOCLAVE. Cool to 45-50°C and dispense into 50-60 mm Petri plates, protecting the medium from light. Test the finished medium for performance using stable, standard control cultures.
06How do I request a bulk quotation, and can you provide a COA?
Yes. This product is available in 500 g, 5 kg, 25 kg. Tell us your application and volume when requesting a quotation; we reply within one working day and can supply the COA, specification sheet, and technical data sheet.
Used in these applications
References
- 1. McCarthy J. A., Delaney J. E. and Grasso R. J., 1961. Measuring coliforms in water. Water Sewage Works, 108:238-243.
- 2. American Public Health Association, Standard Methods for the Examination of Water and Wastewater, current edition, APHA Press, Washington, D.C.