Pseudomonas Isolation HiCynth™ Agar Base

Principle And Interpretation

Pseudomonas Isolation HiCynth™ Agar Base is used for the selective isolation and identification of P. aeruginosa, is a modification of Medium A, originally formulated by King, Ward and Raney (1). It is prepared by replacing animal and vegetable peptones with chemically defined peptones to avoid BSE/TSE risks associated with animal peptones.

Pseudomonas aeruginosa is an important human pathogen commonly found in nosocomial infections. It successfully combines adaptability to a variety of moist environments with a collection of potent virulence factors (2). Pseudomonas infections usually occur at any site where moisture tends to accumulate e. g. tracheostomies, in-dwelling catheters, burns, the external ear and weeping cutaneous wounds (3). The medium contains pigment-enhancing components and the selective agents, triclosan (4,5) which selectively inhibits gram-positive and gram-negative bacteria. The pigment-enhancers i.e. potassium sulphate and magnesium chloride enhance the blue or blue-green pigment production by P. aeruginosa, thus aiding in its identification. Some pyocyanin producing strains may also produce small amounts of fluorescein, resulting in the production of a blue-green to green pigment. HiCynth™ Peptone No.4 provides nitrogenous compounds and other essential growth nutrients. Glycerol is a source of energy and promotes pyocyanin i.e. pigment production which is characteristic of Pseudomonas (5,8). Presumptive Pseudomonas should be further confirmed by performing biochemical tests, as some strains of Pseudomonas do not produce pyocyanin (8).