A modification of the medium described by Brown and Lowbury, Cetrimide Agar is used to selectively cultivatePseudomonasaeruginosa. The quaternary ammonium compound Cetrimide allows the growth of this species while suppressing that of Gram-positive and some Gram-negative microorganisms. Magnesium Chloride and Potassium Sulfate enhance the production of the iron chelators pyoverdin (yellow-green or yellow-brown fluorescent) and pyocianin (blue), whose combination produces a characteristic bright green color, byP.aeruginosa. Pancreatic Digest of Gelatine provides nitrogenous compounds, carbohydrates, vitamins, and minerals for bacterial growth. Agar is the gelifying agent.