All Photos(2)




MacConkey Agar

NutriSelect® Basic, suitable for microbiology

Sign Into View Organizational & Contract Pricing

Enteric bacteria selective medium, MacConkey′s medium
EC Number:
MDL number:



Quality Level




bottle of 250 g
bottle of 500 g


NutriSelect® Basic


light yellow


food and beverages
water monitoring



Citrobacter spp.
Escherichia coli
Gardnerella spp.

General description

MacConkey Agar is used for the isolation, identification, and enumeration of lactose fermenting and lactose non-fermenting enteric bacteria.The media is accepted by the Standard Methods for the Examination of milk and dairy Products and pharmaceutical preparations. Peptone in the media provides nitrogenous and carbonaceous compounds, long-chain amino acids, vitamins, and other essential growth factors. Lactose is the fermentable sugar that causes acid production and a color change of the indicator when the pH of the medium falls below 6.8. Sodium chloride maintains the osmotic equilibrium. The selective action of this medium is attributed to crystal violet and bile salts, which are inhibitory to most species of gram-positive bacteria. Gram-negative bacteria usually grow well on the medium and are differentiated by their ability to ferment lactose. Lactose fermenting strains form red or pink colonies and are surrounded by a zone of acid-precipitated bile. Lactose non-fermenting strains, such as Shigella and Salmonella, form colorless, transparent colonies and typically do not alter the appearance of the medium.


MacConkey Agar is a differential plating medium recommended for the detection and isolation of coliforms and intestinal pathogens from stool, urine, water, and other material.

Biochem/physiol Actions

MacConkey Agar is considered as a selective and differential media. It is useful in differentiating between the lactose fermenting and non-lactose fermenting bacteria. Thus, it is useful in the isolation of gram negative bacteria. Primary plating medium is used to differentiate members of the coliform group.

Features and Benefits

NutriSelect® Basic are powdered culture media offering
  • Quality control with basic growth promotion test
  • Quality assurance acc. to ISO 9001
  • Cost-efficient powdered media

Preparation Note

Suspend 50 g in 1 litre of distilled water. Bring to the boil to dissolve completely. Sterilize by autoclaving at 121°C for 15 minutes. Pour into sterile petri plates. Dry the surface of the gel before inoculation.

Analysis Note

Microbiologically tested.


We offer two media types: the superior granulated GranuCult® and the cost-efficient powdered NutriSelect® culture media, depending on your needs.
The designations basic, plus, or prime are added to indicate the quality control level, from basic quality control to standard QC plus to prime for full regulatory compliance.

Legal Information

GRANUCULT is a registered trademark of Merck KGaA, Darmstadt, Germany
NutriSelect is a registered trademark of Merck KGaA, Darmstadt, Germany

Storage Class Code

11 - Combustible Solids



Personal Protective Equipment

dust mask type N95 (US), Eyeshields, Gloves

Certificates of Analysis (COA)

Search for Certificates of Analysis (COA) by entering the products Lot/Batch Number. Lot and Batch Numbers can be found on a product’s label following the words ‘Lot’ or ‘Batch’.

Already Own This Product?

Documents related to the products that you have purchased in the past have been gathered in the Document Library for your convenience.

Visit the Document Library

Difficulty Finding Your Product Or Lot/Batch Number?

Product numbers are combined with Pack Sizes/Quantity when displayed on the website (example: T1503-25G). Please make sure you enter ONLY the product number in the Product Number field (example: T1503).


Product Number
Pack Size/Quantity

Additional examples:





enter as 1.000309185)

Having trouble? Feel free to contact Technical Service for assistance.

Lot and Batch Numbers can be found on a product's label following the words 'Lot' or 'Batch'.

Aldrich Products

  • For a lot number such as TO09019TO, enter it as 09019TO (without the first two letters 'TO').

  • For a lot number with a filling-code such as 05427ES-021, enter it as 05427ES (without the filling-code '-021').

  • For a lot number with a filling-code such as STBB0728K9, enter it as STBB0728 without the filling-code 'K9'.

Not Finding What You Are Looking For?

In some cases, a COA may not be available online. If your search was unable to find the COA you can request one.

Request COA

Our team of scientists has experience in all areas of research including Life Science, Material Science, Chemical Synthesis, Chromatography, Analytical and many others.

Contact Technical Service