The endotoxin of the following gram negative bacteria does not play any part in the pathogenesis of the natural disease.

Cholera Vibrios also possess lipopolysaccharide O antigen (LPS, endotoxin) as in other gram-negative intestinal bacilli. But unlike other gram-negative bacilli like E.coli, Klebsiella and Pseudomonas, etc. (where endotoxin is the principle virulence factor), LPS apparently plays no role in pathogenesis of cholera but is responsible for the immunity induced by killed vaccine. For Vibrio cholerae the principle virulence factor is the exotoxin, i.e. cholera toxin.