J. clin. Path. (1955), 8, 47. THE USE OF A NEW CETRIMIDE PRODUCT IN A SELECTIVE MEDIUM FOR PSEUDOMONAS PYOCYANEA BY

A selective medium containing 0.1 % cetrimide in nutrient agar has been used here during the past four years for the routine identification of Ps. pyocyanea in burns (Lowbury, 1951). This medium, a modification of those previously de-scribed by Harper and Cawston (1945) and by Hood (1948), has proved convenient and efficient. In October, 1953, the manufacturers announced the production of a modified "cetavlon " which was claimed to be more active against Ps. pyo-cyanea than the old product, and little less active against that organism than against Proteus vul-garis. In view of these observations we have made the following tests to find whether the new cetri-mide is suitable for use in a selective medium for Ps. pyocyanea, and if so at what concentration it should be included. Choice of a Dilution of the New Cetrimide for the Selective Medium Media containing the old and the new cetrimide were compared by methods described by one of us in a previous paper (Lowbury, 1951). The basic medium was " lemco " agar at pH 7.