Bacterial Toxins: How Exotoxins and Endotoxins Cause Tissue Damage and Disease
Bacteria produce toxins that harm the host. These toxins fall into two main groups: exotoxins and endotoxins. Both play a major role in tissue damage and disease.
Exotoxins are proteins that living bacteria release into their surroundings. Many of them act with high specificity. Some attack cell membranes and cause cells to burst. Others disrupt nerve signals or block protein synthesis. As a result, they can produce rapid and severe effects.
Classic examples include diphtheria toxin, tetanus toxin, and cholera toxin. Diphtheria toxin damages the heart and nerves. Tetanus toxin causes muscle spasms. Cholera toxin leads to massive fluid loss from the intestine.
Endotoxins differ in structure and action. They form part of the outer membrane of Gram-negative bacteria. When these bacteria die or break apart, endotoxin is released. The active part is lipopolysaccharide, or LPS.
Endotoxin triggers a strong immune response. It stimulates the release of inflammatory chemicals. In large amounts, this response can damage blood vessels and organs. Consequently, patients may develop fever, low blood pressure, and septic shock.
The two types of toxins therefore cause harm in different ways. Exotoxins often act as precise molecular weapons. Endotoxins mainly drive widespread inflammation. Together they explain many of the serious features of bacterial disease.
Understanding these toxins helps doctors recognise severe infections. It also guides treatment and the development of better vaccines and antitoxins.