Cetrimide Agar Test- Principle, Procedures, Results, Uses


Cetrimide agar test is a biochemical test that is used to identify and differentiate Pseudomonas aeruginosa from other microorganisms. Pseudomonas aeruginosa is a gram-negative rod that can cause various infections in humans, such as urinary tract infections, wound infections, and septicemia. It is also known for producing pigments, such as pyocyanin (blue-green) and fluorescein (yellow-green), that give it a characteristic appearance on culture media.

The test is based on the ability of Pseudomonas aeruginosa to grow in the presence of cetrimide, a quaternary ammonium salt that acts as a cationic detergent. Cetrimide inhibits most other bacteria by affecting their cell membranes and causing the release of nitrogen and phosphorus from the cells. Pseudomonas aeruginosa, however, is resistant to cetrimide and can use it as a source of nitrogen.

Cetrimide agar is a selective medium that contains cetrimide as well as other ingredients that enhance the growth and pigment production of Pseudomonas aeruginosa. These include gelatin peptone, glycerol, sodium chloride, magnesium chloride, and potassium sulfate. The medium has a pH of 7.2 and is solidified with agar.

Cetrimide agar test is used for the isolation and identification of Pseudomonas aeruginosa from clinical and non-clinical specimens, such as water, pharmaceutical products, and environmental samples. It can also be used to detect the ability of an organism to produce pyocyanin and fluorescein, which are indicative of Pseudomonas aeruginosa. The test is simple, rapid, and inexpensive compared to other methods of identification.