182 



Microbes and You 



field of toxin investigation, and in 1892 Pfeiffer reported that the 

 cholera organisms produce a poison that is not excreted during the 

 life of the parent cells. It was Pfeiffer who coined the term 

 endotoxin. 



Repeated injections of sub-fatal doses of exotoxins, or the injec- 

 tion of Toxoms— a toxin that has been detoxified by the addition of 

 formalin— will stimulate the production of protective substances 

 called ANTIBODIES. The stimulating agent is called an antigen, 

 because it causes the injected animals to produce something against 

 the antigen. When an endotoxin-producing organism is intro- 

 duced into an animal, antibodies will be formed, but they will not 

 be antitoxins; they will be antibodies produced against the entire 

 cell substance, of which the toxin may be but a small fraction. 



The comparison of exotoxins and endotoxins below summarizes 

 the principal characteristics of these two types of poisons. 



Location 



Toxicity 



Chemistry of 

 Pure Toxin 



Action of 

 Formalin 

 Inactivation 



Antigenicity 

 Specificity 



EXOTOXINS 



Given off through the cell wall 

 into the medium during growth 

 of the cells. 



Exhibit a high degree of tox- 

 icity. 

 Are proteins. 



Are converted into toxoids. 



Usually inactivated by heat 

 (58-80° C.) in 10 minutes, and 

 by proteolytic enzymes. 

 Will stimulate the formation of 

 antitoxins in animals. 

 Specific for antitoxins. 



ENDOTOXINS 



Remain within the cell until 



the organism is disintegrated 



by autolysis or by physical 



means. 



Are less toxic than exotoxins. 



May be protein, although 

 some contain other complex 

 substances including carbohy- 

 drates. 

 Are not converted into toxoids. 



Exhibit resistance to heat 

 (80-100° C. for 1 hour) and to 

 proteolytic enzymes. 

 Are poor antigens for anti- 

 toxin production. 

 Not specific for antitoxin. 



It is not uncommon for an organism to produce several toxins 

 which react in a number of diverse ways when subjected to dif- 

 ferent tests. Micrococci, for example, produce hemotoxin which 

 dissolves red blood cells; a leucocytic toxin which destroys white 



