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product description
The MacConkey medium is a selective medium for the preferential cultivation of Gram-negative bacteria. This is done by adding bile salts and crystal violet, which can largely inhibit the growth of gram-positive bacteria. However, MacConkey is not suitable for obtaining pure cultures of Gram-negative bacteria from mixed samples containing Gram-negative and Gram-positive bacteria. MacConkey does not serve as a purity control - that's what e.g. B. to use a CLED plate.
The MacConkey medium can also be used as a differential medium. The addition of neutral red serves as a pH indicator, e.g. B. can indicate the pH reduction when lactose is used by the bacteria turning red. Cloudy areas regularly appear around the lactose-positive, red-colored bacteria, which are caused by the precipitation of bile salts as a result of the pH reduction.
For the cultural differentiation of Gram-positive and Gram-negative bacteria, the combination of CLED, MacConkey and Columbia blood CNA is always recommended (Beyaert system, then also Sabouraud-G/C for yeast detection).
