Substituted diazenes: effect on the growth of enterobacteria and possible use as selective agents for isolation of pseudomonads

New medium for the isolation and enumeration of pseudomonads

A new medium containing 200 ppb of 2-hydroxy-2',4,4'-trichlorodiphenyloxide (CH3565) and 10 ppm of cetyl-trimethyl-ammonium bromide (Cetrimide) in tryptic soy agar was developed and tested with 19 pure cultures of Pseudomonas, 20 microorganisms of other genera, commercially prepared ground beef, and laboratory-prepared inoculated ground beef. The new medium, CETCH agar, was compared with an antibiotic-containing medium. CETCH agar provided greater pseudomonad recoveries, a shorter incubation period prior to plate counting, and greater ease of preparation.