Pseudomonas Agar Medium For Detection of Pyocyanin Medium 21 (In accordance with IP 2007)

Principle And Interpretation

Pseudomonas Agar is based on the formulation described by King et al (1) and as recommended in Indian Pharmacopoeia (2) for detecting pyocyanin, a water soluble pigment by Pseudomonas species from pharmaceutical preparation and clinical specimens such as stools, wounds, and urine. (3). Pseudomonas species are commonly isolated pathogen and is the significant causative agent of nosocomial, skin and burn infections. Pseudomonas strains are reported to produce phenazine pigments like Pyocyanin- blue green redox-active secondary metabolite pigment, pyorubin-rust brown pigment, -oxyphenzine- a breakdown product of Pyocyanin, pyoverdin-a water soluble yellow green pigments also known as fluorescein. Pyocyanin is readily recovered in large quantities in sputum from patients with cystic fibrosis, an infection caused by Pseudomonas (4,5). This medium enhances the formation of Pyocyanin and/or pyorubin and reduces that of fluorescein

Pancreatic digest of gelatin provides essential nutrients for growth of Pseudomonas, while glycerol provides carbon and energy to the cell. The pyocyanin pigment diffuses from the colonies of Pseudomonas into the agar and shows blue colouration. Potassium sulphate and magnesium chloride enhances the pyocyanin production and suppresses the fluorescein production. Low content of phosphorous in the medium also aids in inhibiting the production of fluorescein. Some Pseudomonas strains produce small amounts of fluorescein resulting in a blue-green colouration.

Strains of Pseudomonas aeruginosa that may fail to produce Pyocyanin are not detected in this medium. Production of other pigments may mask the presence of Pyocyanin.