Abstract

The idea of the harmful effects of pathogenic bacteria via toxin production has existed since ancient times. In 1872, Klebs hypothesized that "sepsins" were responsible for the formation of toxins produced by staphylococci, although he was unable to prove this hypothesis with evidence. In 1884, Robert Koch discovered that cholera was caused by toxins produced by bacteria rather than the bacteria themselves, demonstrating that bacterial pathogens could grow in the digestive tract without damaging the intestinal wall or nearby organs. However, research and studies have shown that injecting cholera filtrate through the gastrointestinal tract leads to results similar to those shown in real cases of the disease. In 1889, Loeffler revealed that the diphtheria bacillus remained localized at the injection site and was not present in the internal organs, indicating that the toxic substance produced at the injection site had spread into the blood circulation. According to Roux and Yersin, who have isolated several highly toxic bacteria, toxins are the reason behind all the bad things that pathogenic bacteria do. During the nineteenth century, studies widely demonstrated that bacterial toxins were the primary cause of the negative effects of all infectious diseases. As a result, medical research focused primarily on developing antitoxin serums. Exotoxins mostly consist of proteins that cause the immune system to work normally against them, and these toxins are produced by Gram-positive bacteria. However, endotoxins are secreted or released as a result of bacterial decomposition, especially the bacterial cell wall. Exotoxins are more sensitive to heat and may be susceptible to the effects of conditions and substances that do not affect endotoxins. This study represents an overview of most investigations that dealt with the properties of protein-nature exotoxins secreted by pathogenic bacteria, with examples of their production and mode of action.