Endotoxin

Endotoxin is a toxic substance bound to the bacterial cell wall and released when the bacterium ruptures or disintegrates. Endotoxins are lipopolysaccharides (LPS) present in the outer membrane of the cell wall of Gram-negative bacteria, and are released upon lysis of the bacteria. They can cause fever, malaise, and potentially serious complications in humans and animals.

Structure and Function

Endotoxins are part of the outer membrane of the cell wall of Gram-negative bacteria such as Escherichia coli, Salmonella, Shigella, Pseudomonas, Neisseria, Haemophilus influenzae, Bordetella pertussis and others. The endotoxin is a lipopolysaccharide (LPS) whose lipid portion (Lipid A) is an endotoxin. It is this Lipid A that is toxic.

Effects on the Human Body

When endotoxins enter the bloodstream, they can cause a number of harmful effects, including fever, changes in white blood cell count, and low blood pressure. In severe cases, they can lead to septic shock, a life-threatening condition.

Detection and Measurement

Endotoxins can be detected and measured using the Limulus amebocyte lysate (LAL) test. This test is based on the clotting of the blood of the horseshoe crab, Limulus polyphemus, in the presence of endotoxin.

Treatment and Prevention

Treatment of diseases caused by endotoxins involves supportive care and, in some cases, the use of antibiotics to kill the bacteria. Prevention involves good hygiene practices and, in some cases, vaccination.

See Also

• Gram-negative bacteria
• Lipopolysaccharide
• Septic shock
• Limulus amebocyte lysate

Endotoxin Resources
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