A selective isolation procedure for Pseudomonas bacteria.

A selective isolation medium was devised for Pseudomonas bacteria. An antibiotic mixture which contained 10 micrograms per ml of cerexin A, 10 micrograms per ml of nalidixic acid and 30 micrograms per ml of cycloheximide was used. With the antibiotic medium, 58 strains of bacteria presumed to be Pseudomonas which were subdivided into 18 taxonomically different groups were isolated from 3 soil samples with 9% of contaminants. With this method, it was possible to isolate a Pseudomonas bacterium from a sample containing about 400 times as many other Gram-positive and -negative bacteria.