The genus Salmonella is a member of the family Enterobacteriaceae. The genus is composed of Gram negative bacilli that are facultative and flagellated (motile). Salmonellae possess 3 major surface antigens; the H or flagellar antigen (phase 1 and 2), the O or somatic antigen (part of the LPS moiety) and the Vi or capsular antigen (referred to as K in other Enterobacteriaceae). Salmonellae also possess the LPS endotoxin characteristic of Gram negative bacteria. This LPS is composed of an O polysaccharide (O antigen) an R core and the endotoxic inner Lipid A. Endotoxins evoke fever and can activate complement, kinin and clotting factors.