This microbiological analysis employs a specific pH indicator in a medium containing lactose to determine the ability of an organism to ferment lactose. A positive reaction, indicated by a color change from red to yellow, signifies acid production as a byproduct of lactose fermentation. A negative result retains the red color or may turn a deeper red due to alkaline byproducts produced in the absence of fermentation. Gas production is detected by the presence of a bubble in a small inverted Durham tube within the culture medium.
Distinguishing lactose fermenters from non-fermenters is crucial for bacterial identification and classification, playing a vital role in clinical diagnostics, food safety, and environmental monitoring. This simple, inexpensive, and rapid test contributes significantly to identifying bacterial species, enabling timely and appropriate interventions across various applications. Its historical significance lies in its contribution to understanding microbial metabolism and continues to be a fundamental tool in modern laboratories.
