TSI basic principle

TSI E. coli E. coli ferments all three sugars and produces acids to change the pH and color of the medium; production of hydrogen and carbon dioxide forms cracks in the medium TSI agar medium contains glucose, lactose and sucrose; it also contains methyl red the pH indicator

TSI P. vulgaris P. vilgaris ferments sugars to produce acids that change the pH and color of the medium; it also produces H2S gas that reacts with ferrous ammonium sulfate to give the medium a black butt TSI agar medium contains glucose, lactose and sucrose; it also contains methyl red the pH indicator

TSI E. aerogenes E. aerogenes ferments glucose to produce acids that changes the pH and the color of the medium; however, since the cap is kept loose, the acids on the surface of the medium are oxidized and the color of the medium changes back to red TSI agar medium contains glucose, lactose and sucrose; it also contains methyl red the pH indicator