EMB Agar
Also known as：EMB · Eosin Methylene Blue Agar · Holt-Harris and Teague EMB Agar · EMB Agar Modified · Eosin Methylene Blue Agar (Lactose Sucrose)
For the isolation and differentiation of Gram-negative enteric bacilli, including Escherichia coli and Salmonella, Shigella, and Proteus species.
- Category
- Dehydrated Culture Media
- Dissolve per litre
- 40.97 g
- Pack sizes
- 500 g · 5 kg · 25 kg
- Certifications
- ISO 22000 · Halal
Data updated：2026-11-06
Overview
EMB Agar (eosin methylene blue) is the classic selective and differential medium for Gram-negative enteric bacilli. Eosin and methylene blue suppress Gram-positive organisms; lactose and sucrose let fermenters produce acid, so E. coli forms dark colonies with a metallic green sheen, other lactose fermenters appear pink, and Salmonella and Shigella remain colourless. Used to confirm E. coli and isolate enterics from food, water and clinical samples.
Principle
Eosin Methylene Blue Agar follows the formulation of Holt-Harris and Teague, who combined eosin Y and methylene blue for the isolation of enteric pathogens.¹ Peptone supplies nitrogen, amino acids, and peptides, and dipotassium hydrogen phosphate buffers the medium. Eosin Y and methylene blue inhibit Gram-positive organisms to a limited degree and act together as a pH-sensitive indicator system. Lactose and sucrose are the fermentable carbohydrates. Organisms that ferment either sugar produce acid, causing the dyes to precipitate onto the colonies; vigorous lactose fermenters such as Escherichia coli form dark colonies with a characteristic green metallic sheen, while less vigorous fermenters such as Klebsiella and Enterobacter form pink to purple, mucoid colonies without sheen.² The inclusion of sucrose allows sucrose-fermenting organisms that do not ferment lactose to be recognised, so that colourless colonies indicate organisms that ferment neither sugar, including Salmonella and Shigella.³
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 36 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Sterilize by autoclaving at 121°C for 15 minutes. Cool to 45-50°C and swirl to restore the blue colour of the methylene blue and to suspend the precipitate, which is an essential part of the medium. Pour into sterile Petri plates. 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-luxuriant |
| Shigella flexneri | 12022 | good |
| Enterococcus faecalis | 29212 | inhibited-partial |
Product highlights
- Food-grade raw materials, produced in an ISO 22000 certified facility
- Halal certified, suitable for the Malaysian, Indonesian, and Middle Eastern markets
- Manufactured to the standard formulation, 40.97 g per litre
- Performance verified against standard control strains before release (Escherichia coli, Klebsiella aerogenes, Salmonella enterica ser. Typhimurium, Shigella flexneri, 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
Food grade versus laboratory grade
Most culture media suppliers use laboratory-grade raw materials, which are held to lower standards for heavy metal residues, microbial contamination control, and traceability. That is adequate for pure research but not for applications with stricter raw-material requirements. STBIO manufactures with food-grade raw materials throughout, in a facility certified to ISO 22000 food safety management.
- Food microbiology laboratories working to ISO 17025 or equivalent requirements
- Biotech manufacturers exporting fermentation products and needing full raw-material traceability
- Organisations with ESG or compliance audit requirements across their supply chain
- Companies sourcing both Halal and non-Halal products who need one consistent material grade
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 40.97 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, Salmonella, Shigella, Escherichia coli, Klebsiella aerogenes, Salmonella enterica ser. Typhimurium, Shigella flexneri, Enterococcus faecalis. See the cultural response table and the specification sheet.
04Can it be used for food-grade applications?
Yes. It is made from food-grade raw materials in an ISO 22000 certified facility and is suitable for culturing starters for fermented products that are consumed directly.
05How is this product prepared?
Suspend 36 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Sterilize by autoclaving at 121°C for 15 minutes. Cool to 45-50°C and swirl to restore the blue colour of the methylene blue and to suspend the precipitate, which is an essential part of the medium. Pour into sterile Petri plates. 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
Further reading
- FDA BAM Culture Media Cross-Reference: Which Media Each BAM Chapter Uses and the STBIO EquivalentAerobic plate count, coliforms and E. coli, Salmonella, Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Vibrio, Clostridium perfringens, yeasts and moulds and Cronobacter: the media named in each FDA Bacteriological Analytical Manual chapter, matched to Taiwan-made dehydrated media for US laboratories qualifying a second source.
- Which Culture Media Do Taiwan FDA Food Microbiology Methods Specify? Cross-Reference for 21 Announced MethodsAerobic plate count, coliforms, E. coli, Enterobacteriaceae, Salmonella, Staphylococcus aureus, Listeria monocytogenes, lactic acid bacteria, yeasts and moulds, Bacillus cereus, Vibrio parahaemolyticus, Clostridium perfringens and Cronobacter: the media named in each Taiwan FDA (TFDA) announced method, matched to Taiwan-made products.
References
- 1. Holt-Harris J. E. and Teague O., 1916. A new culture medium for the isolation of Bacillus typhosus from stools. J. Infect. Dis., 18:596-600.
- 2. Levine M., 1918. Differentiation of B. coli and B. aerogenes on a simplified eosin-methylene blue agar. J. Infect. Dis., 23:43-47.
- 3. MacFaddin J. F., 1985. Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Williams & Wilkins, Baltimore.