Virulence attributes of the liposaccharides of the HAP group organisms.

The pathogenic potential of purified gram-negative bacterial endotoxin is well documented. However, the role of endotoxin in the disease producing ability of pathogenic organisms, including those of the HAP group, remains in doubt. Endotoxin is not a classic virulence factor, but likely contributes to the pathogenic potential of gram-negative bacteria by activation of host defensive systems which ultimately results in the clinical signs and tissue damage that we recognize as disease. On the other hand, the proinflammatory nature of endotoxin, as well as liposaccharide antigens, play a critical role in the successful elimination of the infecting organism. How the induction of host defensive systems by endotoxin might benefit the infecting organism is difficult to reconcile. In this regard, host response to endotoxin often appears to be in excess of that necessary to clear the infection. Regardless of the role endotoxin might play in the pathogenesis of an infection, liposaccharide antigens are important in the serologically based classification of bacterial strains, are known to contribute to protective immunity, and are useful in the serological diagnosis of infection.