The most common biological activity of bacterial endotoxin is its thermogenicity, and the infusion reaction with chills and fever as the main clinical manifestation is mostly caused by the contamination of bacterial endotoxin by the infusion preparation.
The thermogenicity of endotoxin has the following characteristics:
There are germline differences, and in mammals, humans, cattle, and rabbits are more sensitive to endotoxins, while rats and mice are less sensitive. Humans are probably the most sensitive to endotoxins of all animals, and intravenous administration at a dose of 2 ng kg can raise body temperature by up to 2 . New Zealand white rabbits are very sensitive to the thermogenicity of endotoxins, and are standardized experimental animals for pyrogen identification used in pharmacopoeias in various countries.
Within a certain range, the height of fever is dose-dependent with the time course. The fever reaction of rabbits to endotoxin, small dose causes monophasic heat, large dose causes biphasic heat, the first heat peak appears about 90min after injection, and the second heat peak appears about 3h, forming a very characteristic thermal type. If a very large dose is given, the animal has typical symptoms of septic shock, when the body temperature does not rise but falls.
Endotoxin fever has a more obvious incubation period (refers to the time when the endotoxin is injected until the body temperature rises to 0 above the basal body temperature3 hours). The incubation period of rabbits is usually 15 30min depending on the intravenous dose, while the incubation period of fever can be as long as 90min when humans are injected intravenously with a dose of 2ng kg.
Prone to tolerance. If rabbits receive continuous endotoxin injection, their febrile response weakens day by day, first of all, the second peak of biphasic fever disappears, and the first peak gradually subsides, and the same dose of endotoxin loses the original febrile response. If the endotoxin injection is stopped, the normal febrile response can be restored after 3 weeks.
The pyretic activity is not easy to remove, and the general sterilization method (such as conventional autoclaving) cannot completely destroy the endotoxin, and it takes more than 160 dry heat for 2h to inactivate it.