Cat. no. G18 Cetrimide Selective Agar, USP, 15x100mm Plate, 26ml 10 plates/bag
Cat. no. J330 TSA (Tryptic Soy Agar) / CET (Cetrimide Selective Agar) / MSA (Mannitol Salt Agar), 15x100mm Triplate, 7ml/section 10 plates/bag
Cat. no. J314 Cetrimide Selective Agar (CET) / MacConkey Agar (MAC) / Vogel and Johnson Agar (VJ), 15x100mm triplate, 7ml/section 10 plates/bag


Hardy Diagnostics Cetrimide Selective Agar is recommended for the selective isolation and identification of Pseudomonas aeruginosa.


Cetrimide Selective Agar, USP is recommended by the U.S. Pharmacopeia for use in the growth promotion testing of non-sterile products tests for specified microorganisms.(8)

Cetyltrimethylammonium bromide, a quaternary ammonium, cationic detergent, is the component of Cetrimide Agar which allows for the selective isolation of Pseudomonas aeruginosa. Cetyltrimethylammonium bromide, when in contact with bacteria, causes the release of nitrogen and phosphorous from the bacterial cell. Organisms other than P. aeruginosa are unable to withstand this germicidal activity.

Cetrimide Selective Agar employs the use of 0.03% cetrimide which follows the formulation established by Sawbury and Collins.(6) Both pyocyanin and fluorescein pigment production are enhanced on Cetrimide Agar.


Ingredients per liter of deionized water:*

Pancreatic Digest of Gelatin 20.0gm
Potassium Sulfate 10.0gm
Magnesium Chloride 1.4gm
Cetyltrimethylammonium Bromide 0.3gm
Glycerine 10.0ml
Agar 13.6gm

Final pH 7.2 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.


Storage: Upon receipt store plated media at 2-8ºC. away from direct light. Media should not be used if there are any signs of deterioration (shrinking, cracking, or discoloration), contamination, or if the expiration date has passed. Product is light and temperature sensitive; protect from light, excessive heat, moisture, and freezing.



Specimen Collection: Consult listed references for information on specimen collection.(2-5)

Method of Use: Consult listed references for the correct inoculation procedure.(2-5) Prior to inoculation, the medium should be brought to room temperature. Inoculate from an 18-24 hour old pure culture or directly from the specimen. Streak so as to obtain isolated colonies. Incubate aerobically at 35-37°C. for up to seven days. Observe daily for growth.


The presence of growth is indicative of a positive reaction. Examine colonies under short wavelength (254nm) ultraviolet light for the presence of fluorescein. Visual examination may also reveal the typical yellow-green to blue color which indicates the production of pyocyanin. Both pyocyanin and fluorescein are typically produced by strains of P. aeruginosa .

A negative reaction is denoted by no growth.


Recovery rates for ready-to-use suspensions of lyophilized or water-soluble quantitative microorganism dilutions requiring no preparation or pre-incubation may encounter performance issues with direct plating and growth promotion testing on selective media. Users are advised to refer to the specific manufacturer's package insert for potential limitations using these types of QC organisms.


Standard microbiological supplies and equipment such as loops, other culture media, swabs, applicator sticks, ultraviolet lights, incinerators, and incubators, etc., as well as serological and biochemical reagents, are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Pseudomonas aeruginosa
ATCC® 9027 **
J 18hrs 30-35°C Aerobic Growth; yellow-green to blue colonies
Escherichia coli
ATCC® 8739 **
B 72hrs 30-35°C Aerobic Partial to complete inhibition

** Tested in accordance with USP <62>.(7,8)

User Quality Control


Cetrimide Selective Agar should appear opalescent, with a precipitate, and light amber in color.

P. aeruginosa growing on Cetrimide Selective Agar

Pseudomonas aeruginosa (ATCC® 9027) colonies growing on Cetrimide Selective Agar (Cat. no. G18). Incubated aerobically for 18-24 hours at 35ºC.

E. coli inhibited on Cetrimide Selective Agar

Escherichia coli (ATCC® 8739) growth inhibited on Cetrimide Selective Agar (Cat. no. G18). Incubated aerobically for 48 hours at 35ºC.


1. Anderson, N.L., et al. Cumitech 3B; Quality Systems in the Clinical Microbiology Laboratory, Coordinating ed., A.S. Weissfeld. American Society for Microbiology, Washington, D.C.

2. Versalovic, J., et al. Manual of Clinical Microbiology. American Society for Microbiology, Washington, D.C.

3. Tille, P., et al. Bailey and Scott's Diagnostic Microbiology, C.V. Mosby Company, St. Louis, MO.

4. Isenberg, H.D. Clinical Microbiology Procedures Handbook, Vol. I, II & III. American Society for Microbiology, Washington, D.C.

5. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

6. J. Clin. Path.; 8:47. 1955.

7. The Official Compendia of Standards. USP General Chapter <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests. USP-NF. United States Pharmacopeial Convention Inc., Rockville, MD.

8. The Official Compendia of Standards. USP General Chapter <62> Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms. USP-NF. United States Pharmacopeial Convention Inc., Rockville, MD.

ATCC is a registered trademark of the American Type Culture Collection.