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Abstract More than a century ago, Richard Pfeiffer (1858–1910), a collaborator of Robert Koch at the Institute for Infectious Diseases in Berlin (Germany) discovered that lysates of heat-killed bacteria of the cholera-inducing infectious agent Vibrio cholerae caused toxic shock reactions in guinea pigs. He postulated that the heat-stable toxic substance was localized inside (classical Greek: ‘endo’) the bacterial cell and thus named it endotoxin to distinguish it from the already known exotoxins of Vibrio cholera (Pfeiffer, 1892; and Rietschel & Westphal, 1999). A subsequent work showed that the release of LPS from gram negative microbes does not require the necessity of destruction of the bacterial cell wall, but rather, LPS is secreted as part of the normal physiological activity of membrane vesicle trafficking in the form of bacterial outer membrane vesicles (OMVs), which may also contain other virulence factors and proteins (Kulp & Kuehn, 2010). Nevertheless, it is known that endotoxins are not all toxic, just as bacteria are not all pathogenic. The endotoxins were soon used to characterize the major group of Gram-negative bacteria, i.e., those having a second outer membrane (Martine & Doris, 2003. |