An improved screening technique for isolation of Pseudomonas pseudomallei from clinical specimens

A selective medium consisting of trypticase soy agar with 4% glycerol, 5 mg/l crystal violet, 50 mg/l neutral red and 4 mg/l of gentamicin was devised for isolation of Pseudomonas pseudomallei from clinical specimens. Absorption of neutral red was found to be suitable for differentiating this organism from other bacteria, while gentamicin was effective in selecting Ps. pseudomallei from organisms commonly found in clinical material. The medium was more suitable for screening clinical specimens than MacConkey's agar with colistin-S because it was more selective and allowed multiple specimens to be inoculated on a single plate. Eight thousand clinical specimens from an area endemic for melioidosis were screened on the selective medium. This resulted in the recovery of 8 isolates of Ps. pseudomallei that would not have been detected using routine culture media alone.