Cetrimide Agar Base
(Pseudomonas Selective Agar Base for Microbiology)

EMD Cat. No. 1.05284.0500
500 g


A modification of the medium proposed by BROWN and LOWBURY (1965) for the isolation and differentiation of Pseudomonas aeruginosa from various materials.


This culture medium complies with the recommendations of the United States Pharmacopeia 30 and the European Pharmacopeia 6.

Click here for information about harmonization of USP/EP chapters on Microbiological Examination of Non-sterile Products (formerly called Microbial Limits Test).


Mode of Action Preparation
Experimental Procedure and Evaluation Quality Control
Typical Composition (g/liter) Literature
Picture/Image


Mode of Action
 The use of cetrimide (cetyltrimethylammonium bromide) was recommended by LOWBURY (1951) and other authors; this compound largely inhibits the growth of the accompanying microbial flora. According to LOWBURRY and COLLINS (1955), a concentration of 0.3 g/liter inhibits the accompanying organisms satisfactorily and minimizes interference with the growth of Ps. aeruginosa. The pigment production of Ps. aeruginosa is not inhibited when grown on this medium.
GOTO and ENOMOTO (1970) recommend the addition of 15 µg nalidixic acid/ml to improve the inhibition of the accompanying microbial flora.


Typical Composition (g/liter)
 Peptone from gelatin 20.0; magnesium chloride 1.4; potassium sulfate 10.0; N-cetyl-N,N,N-trimethylammoniumbromide (cetrimide) 0.3; agar-agar 13.6.
 Also be added: Glycerol 10 ml.

Preparation
 Suspend 45.3 g in 1 liter of purified water. Heat to boiling to dissolve completely. Add 10 ml glycerol/liter, autoclave (15 min at 121°C). Pour plates.
pH: 7.2 ± 0.2 at 25°C.
 The plates are turbid and light brown.


Experimental Procedure and Evaluation
 Inoculate by spreading the sample on the surface of the plates.
Incubation: up to 48 hours at 35°C aerobically.
Ps. aeruginosa colonies produce a yellow-green pigment (pyocyanin) and fluoresce under UV light. Further tests should be performed for further identification (HUGH and LEIFSON 1953, KOVÁCS 1956, THORNLEY 1960, BÜHLMANN et al. 1961 etc).

Quality control (spiral plating method)

Test strains
 Inoculum (cfu/ml)
 		Recovery rate %
 		Yellow-green pigment
Pseudomonas aeruginosa ATCC 9027
 		10 - 100 ≥ 30%
 		+
Pseudomonas aeruginosa ATCC 25668
 		10 - 100
 		≥ 30%
 		+
Pseudomonas aeruginosa ATCC 27853
 		10 - 100
 		≥ 30%
 		+
Escherichia coli ATCC 8739
 		≥ 1 - 104
 		No Growth
 		-
Proteus mirabilis ATCC 29906
 		≥ 1 - 104
 		No Growth
 		-
Salmonella typhimurium ATCC 14028
 		≥ 1 - 104
 		No Growth
 		-
Staphylococcus aureus ATCC 6538
 		≥ 1 - 104
 		No Growth
 		-


Additives

EMD Cat. No. Product Pack Size
1.04093.0500 Glycerol 500 ml
1.13203.0001 UV Lamp (366 nm) 1 ea


Literature

DIN Deutsches Institut für Normung e.V.: Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung. Mikrobiologische Verfahren. Nachweis von Pseudomonas aeruginosa. DIN 38411.
 BROWN, V.I., a. LOWBURY, E.J.L.: Use of improved cetrimide agar medium and other culture methods for Pseudomonas aeruginosa. J. Clin. Pathol., 18; 752-756 (1965).
 BUHLMANN, X., FISCHER, W.A., a. BRUHN, J.: Identification of a pyocyanogenic strains of Pseudomonas aeruginosa. J. Bact., 82, 787-788 (1961).
 GOTO, S., a. ENOMOTO, S.: Nalidixic acid cetrimide agar. A new selective plating medium for the selective isolation of Pseudomonas aeruginosa. Japan J. Microbiol., 14; 65-72 (1970).
 HUGH, R., a. LEIFSON, E.: The taxonomic significance of fermentative versus oxidative metabolism of carbohydrates by various gramnegative bacteria. J. Bact., 66; 24-26 (1953).
 KOVÁCS, N.: Identification of Pseudomonas pyocyanea by the oxidase reaction. Nature (Lond.), 178; 703 (1956).
 LOWBURY, E.J.L.: Improved culture methods for the detection of Ps. pyocyanea. J. Clin. Pathol., 4; 66-72 (1951).
 LOWBURY, E.J.L., a. COLLINS, A.G.: The use of a new cetrimide product in a selective medium for Pseudomonas pyocyanea. J. Clin. Pathol., 8; 47-48 (1955).
 THORNLEY, M.J.: The differentiation of Pseudomonas from other gramnegative bacteria on the basis of arginine metabolism. J. Appl. Bact., 23; 37-52 (1960).

United States Pharmacopeia 30

<61> Microbiological Examination of Non-sterile Products: Microbial Enumeration Tests (USP 30, page 89).
<62> Microbiological Examination of Non-sterile Products: Tests for Specified Microorganisms (USP 30, page 93).

European Pharmacopeia 6 (Ph. Eur)
2.6.12 Microbiological Harmonization of Non-sterile Products - Microbial Enumeration Test
2.6.12 Microbiological Harmonization of Non-sterile Products - Tests for Specified Microorganisms


Pseudomonas aeruginosa



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