**5.2 Flagellar antigen (Ag H)**

It is a polymer of flagellin (structural protein of flagella). This antigen is thermolabile, destroyed by heat at 100 ° C by the action of alcohol and by proteolytic enzymes. It is resistant to formalin and loses their agglutinability by antibodies in the presence of alcohol and phenol. Optimum development is achieved on soft liquid media after spending eight hours at 37 ° C (Dumas, 1958). The vast majority of serovars has two genetic systems, and can alternately express two different specificities for their flagellar antigen. It is said that the flagellar antigens of Salmonella are two-phase (Humbert et al., 1998).
