The Direct Pseudomonas Vial (PD-109) is a screening vial for the detection of Pseudomonas species. The Direct Pseudomonas Vial (PD-109) with the addition of the supplement (S2-PSI) is specific for the detection of Pseudomonas aeruginosa. The vial has an assay time of 20 hours for most applications. Following a salmonella selective enrichment protocol, organisms grow in the vial broth medium. The carbon dioxide (CO2) produced diffuses through a membrane layer into a soft agar plug containing a dye indicator. The color change in the dye is read by the instrument. The membrane layer in the vial servers as a barrier, eliminating product interference with the reading window.