S. typhi (Salmonella typhi) or S. enterica serovar Typhi (Salmonella enterica serovar Typhi) is the aetiological agent of Typhoid fever, a serious invasive bacterial disease of humans. Many S. enterica serovars actively invade the mucosal surface of the intestine but are normally contained in healthy individuals by the local immune defence mechanisms. However, S. typhi has the ability to spread to the deeper tissues of humans, including liver, spleen and bone marrow (Ref.1). The most studied S. enterica serovar Typhi strains are Ty2 and strain CT18. The two strains exhibit differences in prophages, insertion sequences, and island structures. While CT18 carries two plasmids, one conferring multiple drug resistance, Ty2 has no plasmids and is sensitive to antibiotics. Salmonella are the [...]