Solid culture medium for selective isolation of Pseudomonas aeruginosa. The Cetrimide Agar is based on the Pseudomonas aeruginosa strains enormous resistance of the Quaternary Ammonium compounds. With regard to the Cetiltrimethyl- Ammonium Bromide there has been growth at 1 g/l concentrations, but in such cases it has been very poor and slow. An inhibitor of 0.3-0.5 g/l , the rest of the fastidious accompanying flora, both gram-positive and gram-negative, as well as other species of pseudomonas are inhibited.