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Relevant genetic characteristics: Whole genome sequences for 20 strains of S. Typhi have been deposited at GenBank as of October, 2013. Genomic characteristics of the sequenced S. Typhi include (i) a genome size ranging from 4.54 to 5.03 Mb, (ii) a mol G+C% of approx. 52, and (iii) 4,419 to 5,336 predicted genes. Plasmids and prophages have been identified in S. Typhi. For example, a resistant plasmid of 218 kb and seven prophages were detected in S. Typhi CT18. Up to ten 15 Salmonella pathogenicity islands (SPIs) have been detected in S. Typhi, these include SPI-1 to 7, 9, 11 to 13, and 15 to 18. Comparative genomics and phylogenetic analyses have shown that S. Typhi (i) had a monophyletic origin approx. 50,000 years ago (ii) has suffered reductive evolution (approx. 200 genes are functionally inactive), (iii) belongs to clade A, according to den Bakker et al. (2011) classification, and (iv) has 349 gene families unique to this serovar.
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