TSI tubes

Triple Sugar Iron

Microbe Library


Glucose Nonfermenter

Uninoculated Side View (A) Front View (A) Front View (B)

Some nonenteric bacteria, such as the pseudomonads, are unable to ferment glucose, lactose, or sucrose. These bacteria derive energy from peptones either aerobically or anaerobically. Utilization of peptones causes the release of ammonia (NH3) resulting in the pH indicator, phenol red, turning from pink to red. Nonglucose ferementers can produce two possible reactions. If the bacteria can metabolize peptones both aerobically and anaerobically, the slant and butt will be red (alkaline over alkaline; K/K). If peptones can only be metabolized aerobically, the slant will be red and the butt will exhibit no change (K/NC). Front View (A) is an example of K/K, and Front View (B) is K/NC

Bacteria producing K/K or K/NC include: Acinetobacter spp. and Pseudomonas spp.

Reference: MacFaddin, J.F. (2000) Biochemical Tests for Identificaion of Medical Bacteria. Lippincott Williams & Wilkins, Philadelphia.

Images © Don Lehman