Pseudomonas CN Agar Base is used for the identification of Pseudomonas aeruginosa by membrane filtration technique. This is based on the detection of pyocyanin production. This medium is a modification of Pseudomonas P Agar (King A Medium - Cat. 1531). ISO 16266 has recommended this medium. Pseudomonas aeruginosa is an opportunist pathogen for humans, capable of growing in water with a low concentration of nutrients. Therefore, natural mineral water and spring water should be checked to be free of Pseudomonas aeruginosa at the time of commercialization. This microorganism can also be found in swimming pool water.

Peptone and casein provide nitrogen, vitamins, minerals, and amino acids essential for growth. Cetrimide is added as a selective agent, and nalidixic acid to suppress contaminants of cetrimide media such as Klebsiella, Proteus and Providencia spp. Potassium sulphate and magnesium chloride provide cations to activate pyocyanin production and enhance pigment production. Bacteriological agar is the solidifying agent.