Produces a CDT (cytolethal distending toxin) activity, which causes DNA damage in intoxicated cells. This damage induces G2/M cell cycle arrest, chromatin fragmentation, cell distention and nucleus enlargement. Localized to the nucleus of infected cells. Expressed only on infection of host cells. Unlike other pathogens possessing a CDT activity, S.typhi does not encode CdtA and CdtC (that form a heterodimeric subunit), which are required for the delivery of CdtB. It means that the CDT activity of S.typhi is strictly dependent on CdtB. Both CDT activity and expression of CdtB require S.typhi internalization into host cells. S.typhi is the only Salmonella serovar that encodes cdtB.