What size inoculum is needed for Salmonella typhi (S typhi) or S paratyphi to cause typhoid fever (enteric fever)?

Updated: Aug 19, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Typhoidal salmonella have no nonhuman vectors. An inoculum as small as 100,000 organisms of typhi causes infection in more than 50% of healthy volunteers. [9] Paratyphi requires a much higher inoculum to infect, and it is less endemic in rural areas. Hence, the patterns of transmission are slightly different.


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