Ornithine CIT Citrate is the sole carbon source. Citrate utilization results in a pH rise and a change in the indicator from green to blue. Sodium Citrate H2S Hydrogen sulfide is produced from thiosulfate. The hydrogen sulfide reacts with iron salts to produce a black precipitate. Urea TDA Tryptophane deaminase forms indolepyruvic acid from tryptophane.
Indolepyruvic acid produces a brownish-red color in the presence of ferric chloride.
Tryptophane VP Acetoin, an intermediary glucose metabolite, is produced from sodium pyruvate and indicated by the formation of a colored complex. Conventional VP test may take up to 4 days, but by using sodium pyruvate, the time required has been shortened. Creatine intensifies the color when tests are positive. Sodium Pyruvate Creatine GEL Liquefaction of gelatin by proteolytic enzymes releases a black pigment which diffuses throughout the tube. GLU MAN INO SOR RHA SAC MEL AMY ARA Utilization of the carbohydrate results in acid formation and a consequent pH drop.