Fig. 9. Model for the delivery and mechanisms of action of Salmonella typhi CdtB. S. typhi enters host cells and reaches an intracellular compartment where cdtB expression can occur and where CdtB can be subsequently retrotranslocated to the cytosol or transported to a compartment where this retrotranslocation can take place. CdtB is then transported to the nucleus, where it triggers the DNA damage responses, including cell cycle arrest and cytoplasmic distention, through its DNase activity (see Discussion for details).