Cetrimide agar is a type of agar used for the selective isolation of the gram-negative bacterium, Pseudomonas aeruginosa.^[1] As the name suggests, it contains cetrimide, which is the selective agent against alternate microbial flora.^[2] Cetrimide also enhances the production of Pseudomonas pigments such as pyocyanin and pyoverdine, which show a characteristic blue-green and yellow-green colour, respectively.^[3][4]

Cetrimide agar is widely used in the examination of cosmetics, pharmaceuticals and clinical specimens to test for the presence of Pseudomonas aeruginosa.^[1]