Disease pathophysiology
Human challenge studies suggest that bacteria passing through the gastric acid barrier after ingestion require an infectious dose between 103–104 bacteria for S Typhi and S Paratyphi A.29,30 Evidence from other enteric infections suggests that reduced gastric acidity, due to gastrectomy or proton pump inhibitor treatment, could reduce the inoculum required.31 Past infection with Helicobacter pylori is a further suggested risk factor.32
The bacteria pass through the wall of the ileum through M cells overlying the Peyers patches and are then ingested by monocyte-macrophage cells in the submucosa and mesenteric lymph nodes (figure 2).33,34 The bacteria survive intracellularly and travel via the lymphatic system and bloodstream to the reticuloendothelial system (liver, spleen, and bone marrow).35 After multiplication in the reticuloendothelial system, re-invasion of the bloodstream coincides with the onset of symptoms.33 The typical incubation period can vary according to the quantity of bacteria ingested but is typically 7–21 days, occasionally as short as 2 days, and with the majority of cases within 28 days.
#pedsky A recent Seminar explores the evidence supporting effective case management of patients with suspected enteric fever ( #Typhoid & #paratyphoid )
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