Lecithinase Test (Nagler’s Reaction)- Principle, Procedure, Results


Lecithinase is a type of phospholipase enzyme that can hydrolyze lecithin, a major component of cell membranes. Some bacteria can produce lecithinase as a virulence factor that helps them to damage host cells and tissues. Lecithinase test (also known as Nagler’s reaction) is a biochemical test that can detect the presence of lecithinase in bacterial cultures. It is based on the observation that lecithinase-producing bacteria can cause a visible change in the appearance of egg yolk agar, a culture medium that contains lecithin from egg yolk.

Lecithinase test was first described by A. Nagler in 1901, who used it to differentiate between Clostridium perfringens (formerly known as C. welchii) and other clostridia. C. perfringens is a Gram-positive, anaerobic, spore-forming bacterium that causes gas gangrene and food poisoning in humans and animals. It produces a potent lecithinase called alpha-toxin (or phospholipase C) that can degrade phospholipids in cell membranes and cause tissue necrosis and hemolysis. Nagler observed that C. perfringens colonies on egg yolk agar produced a characteristic opaque halo around them, indicating the hydrolysis of lecithin in the medium.

Since then, lecithinase test has been widely used as a presumptive identification method for C. perfringens and other lecithinase-producing bacteria, such as Bacillus cereus, Bacillus anthracis, Pseudomonas aeruginosa, and Burkholderia spp. Lecithinase test can also help to differentiate between various species and strains of bacteria based on their lecithinase activity and the size and shape of the halo zone. Lecithinase test is simple, inexpensive, and easy to perform and interpret. However, it is not a confirmatory test and should be supplemented by other biochemical and molecular tests for accurate identification of bacteria.

In this article, we will discuss the principle, procedure, results, applications, and limitations of lecithinase test in detail. We will also provide some examples of bacteria that test positive and negative for lecithinase production. We hope that this article will help you to understand the importance and significance of lecithinase test in microbiology.