PYROGENS, What is it?

 

The term pyrogen is used to describe any substance that causes fever. Exogenous pyrogens are derived from outside the patient; most are microbial products, microbial toxins, or whole microorganisms. The classic example of an exogenous pyrogen is the lipopolysaccharide endotoxin produced by all gram-negative bacteria. Endotoxins are potent not only as pyrogens but also as inducers of various pathologic changes in gram-negative infections. Another group of potent bacterial pyrogens is produced by gram-positive organisms and includes the enterotoxins of Staphylococcus aureus and the group A and B streptococcal toxins, also called superantigens. One staphylococcal toxin of clinical importance is the toxic shock syndrome toxin associated with isolates of S. aureus from patients with toxic shock syndrome. Like the endotoxins of gram-negative bacteria, the toxins produced by staphylococci and streptococci cause fever in experimental animals when injected intravenously at concentrations of <1 µg/kg of body weight. Endotoxin is a highly pyrogenic molecule in humans: a dose of 2 to 3 ng/kg produces fever and generalized symptoms of malaise in volunteers.

Source: Harrison_s_Principles_of_Internal_Medicine_16th_Edition