The lifestyle of
Typhi in the human host and implications for diagnostics. A; For S. Typhi infection, the organism normally enters the human host through oral ingestion of an infectious dose. B; S. Typhi does not replicate in large numbers in the intestine and shedding may be sporadic and limited. C; Invasion occurs through the terminal ileum, perhaps a short time after ingestion, M cells may be the preferred portal of entry. D; S. Typhi is transferred to monocytic cells and is trafficked to the reticulo-endothelial system, potentially in a semi-dormant state. E; S. Typhi re-emerges at an unknown time from the reticulo-endothelial system, possibly as the acquired immune response is activated, and re-enters the blood stream in low numbers. F; S. Typhi seeds into the liver, the gall bladder and the bone marrow where it can reside and may be detected for months or years. G; S. Typhi can enter into the bile duct and be shed sporadically, potentially in high numbers into the environment via the intestine.