12.6.3: Cetrimide Agar (Pseudomonas P agar)

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Note

Video review: Cetrimide Agar

Cetrimide agar contains the chemical cetrimide (cetyl timethylammonium bromide) for the selective inhibition of most bacteria other than Pseudomonas. The medium also stimulates Pseudomonas aeruginosa to produce a number of pigmented compounds, including pyoverdin and pyocyanin. The green water soluble pigment characteristic of Pseudomonas aeruginosa is due to production of a green to blue water-soluble toxin called pyocyanin (see Fig. \(\PageIndex{1)\)). A fluorescent siderophore called pyoverdin, often produced by Pseudomonas, will typically fluoresce when the plate is placed under a short wavelength ultraviolet light (see Fig. \(\PageIndex{2)\)). After a few minutes at room temperature, the plate loses its fluorescence. The fluorescence, however, can be restored by placing the plate back at 37°C for several minutes.

Fig. \(\PageIndex{1)\): Pseudomonas aeruginosa Growing on Cetrimide Agar with a Positive Oxidase Test	Fig. \(\PageIndex{2)\): Pseudomonas aeruginosa Growing on Cetrimide Agar and Fluorescing Under Ultraviolet Light

Note the production of pyocyanin, a green water soluble pigment, and the positive oxidase test.	Note the production of fluorescein, a compound that fluoresces under short wavelength ultraviolet light.
Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0

Contributors and Attributions

Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)