Toxins are poisonous substances - products of microorganisms, possesses high molecular weight and antigenic properties.
Bacterial toxins are divided into two groups - exotoxins and endotoxins, which differ in their properties and the nature of the actions on the body.
Exotoxins produced by microbes in the environment, possess highly pronounced toxicity. For example, the minimum lethal dose of native (raw) diphtheria toxin for Guinea pigs are equal is 0.0002 ml, tetanus - 0,005 ml, and botulinum - 0,0001 Jr. Activity purified toxins in several hundred times higher.
Action exotoxins on the body manifests itself through a certain incubation period. Endotoxins operate through a shorter period of time.
Endotoxins are structural components of the bacterial cell and enter into the environment only after its destruction. Endotoxins in its toxicity is far below the exotoxins. Exotoxins - thermolabile substances: most of them destroyed at a temperature of 60-80 degrees per day for 10 to 20 minutes Endotoxins are highly resistant to heat: collapse at a higher temperature or during prolonged boiling. Exotoxins less resistant to various physical and chemical factors compared to endotoxins. Freezing and thawing of toxins no visible impact on their strength. Toxins are well preserved in the dried state.
Action formalin and heat exotoxins deprives their toxic properties, but retains the immunogenicity. On this principle, developed obtaining anatoxin (see)is used to prevent a number of infections. Attempts to gain anatoxinum of endotoxins were unsuccessful. Most of exotoxins are used during the titration relevant antitoxic serum.
A characteristic feature for exotoxins is expressed antigenicity is the ability to call when introduced into the body, the antibodies that has a high degree of specificity. This circumstance allows to make the production conditions for treatment and preventive serum against diseases caused by pathogens that produce exotoxins.
Most of exotoxins is produced by gram-positive bacteria. However, according to some researchers, exotoxins are able to produce and some gram-negative species (pathogens of plague, pertussis, Shigella dysenteriae Grigorieva - Sigi).
Biological properties of a number of products of animal and vegetable origin is very close to microbial toxins (e.g., vegetable poisons abrin, Robin, Razin; animal poisons snakes, Scorpions, spiders).