Cetrimide Agar- Composition, Principle, Preparation, Results, Uses


Cetrimide agar is a selective and differential medium that is used for the isolation and identification of Pseudomonas aeruginosa, a gram-negative, rod-shaped, opportunistic pathogen that can cause various infections in humans and animals. Pseudomonas aeruginosa is known for its ability to produce pigments, such as pyocyanin and fluorescein, that give it a characteristic green color on cetrimide agar. Cetrimide agar contains cetrimide, a quaternary ammonium salt that inhibits the growth of most bacteria except Pseudomonas aeruginosa, which is resistant to it. Cetrimide agar also contains other ingredients that enhance the production of pigments by Pseudomonas aeruginosa, such as magnesium chloride, potassium sulfate, and glycerol. Cetrimide agar was first developed by Lowburry in 1948 as a modification of Tech Agar, which was originally devised by King et al. in 1939. Cetrimide agar is widely used in clinical and environmental microbiology for the detection and enumeration of Pseudomonas aeruginosa from various specimens. Cetrimide agar can also be used to determine the ability of an organism to produce pyocyanin and fluorescein, which are important virulence factors of Pseudomonas aeruginosa. Cetrimide agar is easy to prepare and interpret and has a high specificity and sensitivity for Pseudomonas aeruginosa. However, cetrimide agar also has some limitations, such as the toxicity of cetrimide, the variability of pigment production by different strains of Pseudomonas aeruginosa, and the possibility of false positive or negative results due to other bacteria that may grow or produce pigments on cetrimide agar. Therefore, cetrimide agar should be used in conjunction with other tests and procedures to confirm the identity of Pseudomonas aeruginosa.

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