The use of a new cetrimide product in a selective medium for Pseudomonas pyocyanea.

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 described 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. pyocyanea than the old product, and little less active against that organism than against Proteus vulgaris. In view of these observations we have made the following tests to find whether the new cetrimide is suitable for use in a selective medium for Ps. pyocyanea, and if so at what concentration it should be included.