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NCBI PD link for serovar Typhi: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#(taxgroup_name:%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Typhi%22)

Genetic characteristics: Serovar Typhi has been found to be monophyletic. Parkhill et al. sequenced the complete genome (4,809,037 bp) of Salmonella Typhi (CT18) and found this isolate exhibited substantial genetic decay with over 200 pseudogenes, including homologs of key Salmonella Typhimurium virulence genes (e.g., sopE2 and fliB), potentially explaining its human-restricted host specificity. This isolate carries two plasmids: a 218,150 bp multidrug-resistant IncHI1 plasmid (pHCM1) and a 106,516 bp cryptic plasmid (pHCM2) phylogenetically linked to a virulence plasmid of Yersinia pestis. Additionally, it harbors up to 15 Salmonella pathogenicity islands (SPIs 1–7, 9, 11–13, and 15–18). Comparative genomics and phylogenetic analyses have shown that serovar Typhi (i) had a monophyletic origin (ii) emerged approx. 30,000 to 50,000 years ago (iii) belonged to clade A, according to den Bakker et al. (2011) classification, and (iv) had 349 gene families unique to this serovar.

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Recent studies reveal that the Rab GTPase Rab32 and its guanine nucleotide exchange factor BLOC-3 form a conserved pathway that both restricts Salmonella Typhi to human hosts and mediates its killing in macrophages of non-susceptible species. These proteins, previously recognized for their role in intracellular membrane trafficking—particularly in melanin synthesis through enzyme transport to melanosomes—are now identified as central players in innate immunity against typhoidal Salmonella. Following intestinal invasion, serovar Typhi effectively evades host defenses through multiple mechanisms: it avoids TLR4 recognition, escapes the classical complement pathway, and resists oxidative killing—primarily through production of its protective Vi capsular polysaccharide.  More specifically, the TviA regulatory protein orchestrates key virulence strategies through its dual regulatory function: (1) suppressing flagellin-induced inflammatory responses and (2) activating expression of the immunoevasive Vi capsular polysaccharide. These virulence factors are encoded within SPI-7, which harbors the viaB locus (Vi capsule genes) along with additional pathogenicity determinants including type III secretion system, SopE and a type IVB pilus assembly system.

Animal reservoir: Salmonella Typhi is a human-restricted serovar.

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1. https://pubmed.ncbi.nlm.nih.gov/25208300/
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC7706954/
3. https://www.who.int/news-room/fact-sheets/detail/typhoid#:~:text=As%20of%202019%20estimates%2C%20there,children%20are%20at%20highest%20risk
4. https://www.cdc.gov/vaccines/hcp/current-vis/typhoid.html
5. https://www.cdc.gov/typhoid-fever/about/index.html
6. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2025.1547190/full
7. https://www.nature.com/articles/35101607
8. https://academic.oup.com/cid/article/45/Supplement_1/S29/357357?login=true
9. https://bmcgenomics.biomedcentral.com/articles/10.1186/1471-2164-12-425
10. https://pmc.ncbi.nlm.nih.gov/articles/PMC3175032/
11. https://www.cdc.gov/typhoid-fever/php/rep-strain/index.html
12. https://pmc.ncbi.nlm.nih.gov/articles/PMC7695120/
13. https://www.annualreviews.org/deliver/fulltext/micro/68/1/annurev-micro-091313-103739.pdf?itemId=/content/journals/10.1146/annurev-micro-091313-103739&mimeType=application/pdf
14. https://link.springer.com/chapter/10.1007/978-3-319-32189-9_17
15. https://academic.oup.com/femsre/article/45/5/fuab014/6159486
16. https://www.nature.com/articles/s41572-023-00480-z
17. https://academic.oup.com/femsre/article/45/5/fuab014/6159486
18. https://pmc.ncbi.nlm.nih.gov/articles/PMC6128363/
19. https://pmc.ncbi.nlm.nih.gov/articles/PMC2622843/
20. https://www.theguardian.com/world/2023/apr/02/typhoid-outbreak-on-refugee-ship-in-netherlands-traced-to-raw-sewage
21. https://archive.cdc.gov/www_cdc_gov/salmonella/2010/frozen-fruit-pulp-8-25-10.html#:~:text=Outbreak%20Investigation&text=Among%20interviewed%20ill%20persons%2C%207,brand%20frozen%20mamey%20fruit%20pulp.
22. https://pubmed.ncbi.nlm.nih.gov/15712078/
23. https://jamanetwork.com/journals/jamainternalmedicine/article-abstract/216736
24. https://www.jstor.org/stable/30085190?seq=1
25. https://pubmed.ncbi.nlm.nih.gov/11092435/
26. https://pmc.ncbi.nlm.nih.gov/articles/PMC2490935/
27. https://ajph.aphapublications.org/doi/pdf/10.2105/AJPH.28.5.644
28. https://ajph.aphapublications.org/doi/10.2105/AJPH.2023.307434
29. https://pmc.ncbi.nlm.nih.gov/articles/PMC3959940/