TSI Agar (Triple Sugar Iron Agar)

Triple Sugar Iron Agar is an agar medium used as a differential medium for the presumptive identification of enteric bacteria. The medium contains no growth inhibitors and most organisms grow, including gram positive organisms and yeasts. Phenol red indicates fermentation of the carbohydrates dextrose, sucrose and lactose. Ferric ammonium citrate is the hydrogen sulfide indicator, causing a blackening in the middle and upper portions of the slant.