S. enterica has an extraordinarily large number of serovars or strains—up to 2000 have been described.[2] Salmonella enterica Serovar Typhi (historically elevated to species status as S. typhi) is the disease agent in typhoid fever. The genome sequences of Serovar Typhi has been established.[3] Salmonella enterica Serovar Typhimurium (also known as S. typhimurium) can lead to a form of human gastroenteritis sometimes referred to as salmonellosis. The genome sequences of serovar Typhimurium LT2[4] have been established. Also an analysis of the proteome of Typhimurium LT2 under differing environmental conditions has been performed [5]. Salmonella enterica Serovar Paratyphi A has been identified.[6] It is associated with paratyphoid fever. It is sometimes known as Salmonella paratyphi. Most cases of salmonellosis are caused by food infected with S. enterica, which often infects cattle and poultry, though also other animals such as domestic cats and hamsters[7] have also been shown to be sources of infection to humans. However, investigations of vacuum cleaner bags have shown that households can act as a reservoir of the bacterium; this is more likely if the household has contact with an infection source, for example members working with cattle or in a veterinary clinic. Raw chicken and goose eggs can harbor S. enterica, initially in the egg whites, although most eggs are not infected. As the egg ages at room temperature, the yolk membrane begins to break down and S. enterica can spread into the yolk. Refrigeration and freezing do not kill all the bacteria, but substantially slow or halt their growth. Pasteurizing and food irradiation are used to kill Salmonella for commercially-produced foodstuffs containing raw eggs such as ice cream. Foods prepared in the home from raw eggs such as mayonnaise, cakes and cookies can spread salmonella if not properly cooked before consumption. Secreted proteins are of major importance for the pathogenesis of infectious diseases caused by Salmonella enterica. A remarkable large number of fimbrial and non-fimbrial adhesins are present in Salmonella and mediate biofilm formation and contact to host cells. Secreted proteins are also involved in host cell invasion and intracellular proliferation, two hallmarks of Salmonella pathogenesis.[8]