MacConkey Agar
Also known as：MAC · MacConkey Agar w/ 0.15% Bile salts · CV and NaCl · MAC Agar · MacConkey Agar with Crystal Violet · MacConkey Agar (harmonized) · MCA
For the selective isolation and differentiation of Gram-negative enteric bacilli on the basis of lactose fermentation.
- Category
- Dehydrated Culture Media
- Dissolve per litre
- 50.03 g
- pH (25 °C)
- 7.1 ± 0.5
- Pack sizes
- 500 g · 5 kg · 25 kg
- Certifications
- ISO 22000 · Halal
Data updated：2026-11-06
Brand cross-reference：BD Difco MacConkey Agar · Oxoid MacConkey Agar No. 3 · Merck MacConkey Agar（USP <62>、EP 2.6.13） Brand cross-reference
- Storage
- Store at 2–8 °C in sealed, dry, clean conditions.
- Shelf life
- 36 months from manufacture date when stored as directed.
- Allergens
- Milk, Soy
Overview
MacConkey Agar is the most widely used selective and differential medium for Gram-negative enteric bacilli. Bile salts and crystal violet suppress Gram-positive organisms, while lactose with neutral red turns lactose fermenters such as E. coli and Klebsiella pink to red, leaving non-fermenters such as Salmonella and Shigella colourless. It is used for coliform testing and enteric isolation from food, water and clinical samples.
Principle
MacConkey Agar derives from the bile salt–neutral red medium described by MacConkey for the differentiation of lactose-fermenting from non-fermenting enteric bacteria.¹ Pancreatic digest of gelatin and peptones supply nitrogen, amino acids, and peptides, and lactose serves as the fermentable carbohydrate. Sodium chloride maintains the osmotic equilibrium. Bile salts and crystal violet inhibit Gram-positive organisms, making the medium selective for Gram-negative bacilli. Organisms that ferment lactose produce acid, which lowers the pH around the colony; neutral red is absorbed, giving pink to red colonies that may be surrounded by a hazy zone of precipitated bile. Non-lactose-fermenting organisms such as Salmonella and Shigella do not produce acid and form colourless, transparent colonies.³ The medium is specified in the pharmacopoeias for the detection of Escherichia coli in non-sterile products.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.
Specifications
| Parameter | Specification |
|---|---|
| pH (at 25°C) | 7.1 ± 0.5 |
Release specifications. Actual values are reported on the COA supplied with each batch.
Directions
Suspend 50 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. Mix well and pour into sterile Petri plates. Test the finished medium for performance using stable, standard control cultures.
Cultural response
| Test organism | ATCC | Growth |
|---|---|---|
| Escherichia coli | 8739 | good-luxuriant |
| Salmonella enterica ser. Typhimurium | 14028 | good-luxuriant |
| Proteus mirabilis | 12453 | good |
| Staphylococcus aureus | 6538 | inhibited |
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, 50.03 g per litre, pH 7.1 ± 0.5
- Performance verified against standard control strains before release (Escherichia coli, Salmonella enterica ser. Typhimurium, Proteus mirabilis, Staphylococcus aureus)
- 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
FDA BAM methods
This product corresponds to a medium used in the chapters of the US FDA Bacteriological Analytical Manual (BAM), the reference methods for FDA regulatory testing. Follow the current online edition of each chapter.
- FDA BAM Chapter 5: SalmonellaBAM Chapter 5Confirmation / biochemicalNamed in the method as：MacConkey agar
- FDA BAM Chapter 6: ShigellaBAM Chapter 6Isolation plateNamed in the method as：MacConkey agar
- FDA BAM Chapter 8: Yersinia enterocoliticaBAM Chapter 8Isolation plateNamed in the method as：MacConkey agar
BAM specifies methods and media formulations; it does not certify brands. Add supplements as the chapter requires, and verify media against reference strains under your quality system.
Frequently asked questions
01Does this medium meet FDA BAM methods?
BAM specifies methods and formulations, not brands. This product corresponds to a medium used in: FDA BAM Chapter 5: Salmonella（BAM Chapter 5）: Confirmation / biochemical; FDA BAM Chapter 6: Shigella（BAM Chapter 6）: Isolation plate; FDA BAM Chapter 8: Yersinia enterocolitica（BAM Chapter 8）: Isolation plate. It is manufactured to the standard formulation and ships with a COA per batch; add supplements as the chapter requires and follow the current online edition.
02Can 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.
03How much powder per litre?
Use 50.03 g per litre of deionised water; pH after sterilisation 7.1 ± 0.5. Preparation and sterilisation conditions are given on the specification sheet.
04Which organisms is it suitable for?
Coliforms, Gram-negative, E. coli, Salmonella, Shigella, Escherichia coli, Salmonella enterica ser. Typhimurium, Proteus mirabilis, Staphylococcus aureus. See the cultural response table and the specification sheet.
05What are the equivalent brand products and standard methods?
Cross-reference: BD Difco MacConkey Agar, Oxoid MacConkey Agar No. 3, Merck MacConkey Agar. Standard methods: USP <62>, EP 2.6.13. Formulations may differ slightly between makers; refer to the specification sheet.
06Can 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.
07How is this product prepared?
Suspend 50 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. Mix well and pour into sterile Petri plates. Test the finished medium for performance using stable, standard control cultures.
08How should it be stored, and what is the shelf life?
Store at 2–8 °C in sealed, dry, clean conditions. 36 months from manufacture date when stored as directed.
09How 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.
- Dehydrated Culture Media (DCM) ApplicationsDCM from STBIO MEDIA is widely used in food microbiology testing, pharmaceutical and biotech quality control, clinical diagnostics, industrial fermentation…
References
- 1. MacConkey A. T., 1905. Lactose-fermenting bacteria in faeces. J. Hyg., 5:333-379.
- 2. United States Pharmacopeia, current edition. Chapter <62> Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms, USP-NF, Rockville, MD.
- 3. MacFaddin J. F., 1985. Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Williams & Wilkins, Baltimore.