This culture medium complies with the recommendations of the United States Pharmacopeia XXVI (2003) and the European Pharmacopeia II and is equivalent to the medium specified in the DIN Norm 38411.
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/litre 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/litre)
Peptone from gelatin 20.0; magnesium chloride 1.4; potassium sulfate 10.0; N-cetyl-N,N,Ntrimethylammoniumbromide (cetrimide) 0.3; agar-agar 13.0.
Also be added:
Glycerol 10 ml.
Suspend 44.5 g/litre, add 10 ml glycerol/litre, autoclave (15 min at 121 °C). Pour plates.
pH: 7.0 ± 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, KOVACS 1956, THORNLEY 1960, BÜHLMANN et al. 1961 etc)