A Comparison of the British Pharmacopoeia (1973) and United States Pharmacopeia (1975) Methods for Detecting Pseudomonads

The British Pharmacopoeia (Anon. 1973) test for contamination by pseudomonads and the United States Pharmacopeia (Anon. 1975) test for the detection of Pseudomonas aeruginosa have been evaluated using type cultures representative of a wide spectrum of Pseudomonas spp. Media containing cetrimide are recommended by both Pharmacopoeias for the detection of pseudomonads. Of the 28 strains tested only five were detected by the BP method and 11 by the USP method. However, only one strain of P. aeruginosa failed to be detected using the USP method. A correlation between m.i.c. values for cetrimide and detection of the organisms was noted. The BP method failed to detect organisms with m.i.c. values of ± 0.03% whilst the USP method did not detect strains with m.i.c. values ± 0.015%.