Background of the antigen
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 antigens; the "H" or flagellar antigen (phase 1 & 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. The commonest Salmonella serotype associated with food borne infections in humans is Salmonella enteriditis and in particular phage type 4 (PT4). Salmonella Enteriditis bacteria may be found in the intestinal tracts of livestock, poultry, dogs, cats and other warm-blooded animals. This strain is only one of about 2,000 kinds of Salmonella bacteria; it is often associated with poultry and eggs.
