MacConkey Agar w/o Crystal Violet

Separate rapidly growing mycobacteria on the basis of its taxonomy using Thermo Scientific™ Remel™ MacConkey Agar w/o Crystal Violet. This agar is a modification of the original MacConkey Agar formulated in 1905¹. In 1974 investigators observed that certain strains of mycobacteria expected to grow on MacConkey Agar failed to do so². Kubica et al. evaluated two formulations of MacConkey Agar for isolation of rapidly growing mycobacteria. MacConkey Agar w/o Crystal Violet provided for better recovery and differentiation of rapid growers, such as Mycobacterium fortuitum-chelonae complex.

Mycobacterium fortuitum is a bacteria that can cause infections of many areas of the body including the skin, lymph nodes, and joints. It belongs to a group of bacteria known as nontuberculous Mycobacterium, as it is different from the Mycobacterium that causes tuberculosis. This media separates rapidly growing mycobacteria on the basis of its taxonomy using MacConkey Agar w/o Crystal Violet.

This medium contains peptones that provides nitrogenous nutrients and amino acids essential for bacterial growth. This modification of MacConkey Agar has a higher concentration of bile salts and does not contain crystal violet. The elimination of crystal violet permits the growth of gram-positive cocci and acid-fast bacilli. This test is valuable in the taxonomic separation of the rapidly growing acid-fast bacilli³. Lactose is the fermentable carbohydrate. During lactose fermentation, a local pH drop around the colony causes a color change in the pH indicator, neutral red, and bile precipitation develops. Bile salts mixture is the selective agent. Sodium chloride maintains the osmotic balance of the medium. Agar is the solidifying agent.

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Remel™ and Oxoid™ products are now part of the Thermo Scientific brand.