Comparative genomic analysis between typhoidal and non-typhoidal Salmonella serovars reveals typhoid-specific protein families.

The genus Salmonella contains more than 2600 serovars. While most cause a self-limiting gastroenteritis, four serovars, S. Typhi, S. Paratyphi A, B and C, elicit typhoid, a potentially fatal systemic infection. Because of the prevalence in certain regions, such as South Asia, and the disease severity of typhoidal Salmonella infections, comprehensive studies are needed to elucidate the pathogenesis of diseases caused by these typhoidal serovars. We performed comparative genomic analyses on eight human typhoidal strains and 27 non-human typhoidal Salmonella strains to elucidate their evolutionary relationships and identify the genes specific to the four typhoidal serovars. Our results indicate that Salmonella may have an open pan-genome. A core-genome based phylogeny demonstrated that divergence between S. Paratyphi A and S. Typhi took place not long ago and S. Paratyphi B shared a recent common ancestor with S. Paratyphi C. Of great interest, the divergence between S. Paratyphi B and S. Paratyphi C was shown to be more recent than that between S. Paratyphi A and S. Typhi. Alignment and comparisons of the genomes identified unique complements of protein families to each of the typhoidal serovars. Most of these protein families are phage related and some are candidate virulence factors. Importantly, we found 88 protein families specific to two to three of the four typhoidal serovars. All but two of the 88 genes are present in S. Typhi, with a few in the three paratyphoidal serovars but none in the non-human typhoidal serovars. Most of these genes are predicted to encode hypothetical proteins and some are known to code for virulence factors such as Vi polysaccharide related proteins. By comprehensive genomic comparisons, we identified protein families specific to the human typhoidal serovars, which will greatly facilitate investigations on typhoid pathogenesis.

Zou QH ，Li RQ ，Liu GR ，Liu SL ... -  《-》

Genetic determinants and polymorphisms specific for human-adapted serovars of Salmonella enterica that cause enteric fever.

Tracz DM ，Tabor H ，Jerome M ，Ng LK ，Gilmour MW ... -  《-》

Salmonella paratyphi C: genetic divergence from Salmonella choleraesuis and pathogenic convergence with Salmonella typhi.

Liu WQ ，Feng Y ，Wang Y ，Zou QH ，Chen F ，Guo JT ，Peng YH ，Jin Y ，Li YG ，Hu SN ，Johnston RN ，Liu GR ，Liu SL ... -  《PLoS One》

Loss of function of metabolic traits in typhoidal Salmonella without apparent genome degradation.

Machado LFM ，Galán JE 《mBio》

Clinical pathogenesis of typhoid fever.

Raffatellu M ，Wilson RP ，Winter SE ，Bäumler AJ ... -  《Journal of Infection in Developing Countries》