Vi capsular polysaccharide (Vi) was first identified as a virulence antigen of Salmonella typhi, the causative agent of typhoid fever in humans; it renders S. typhi resistant to phagocytosis and the action of serum complement. However, the role of Vi during the infection of intestinal epithelium with S. typhi is not completely understood. We show here that Vi can interact with a model human int...

UNLABELLED Expression of capsular polysaccharides is a variable trait often associated with more-virulent forms of a bacterial species. For example, typhoid fever is caused by the capsulated Salmonella enterica serovar Typhi, while nontyphoidal Salmonella serovars associated with gastroenteritis are noncapsulated. Here we show that optimization of the immune evasive properties conferred by the ...

Salmonella typhi is the causal organism for the typhoid fever. Typhoid disease is a problem in those developing countries where lack of sanitation, poor water supplies and exposure to unhygienic and polluted environment is a part of routine life of majority of population. Salmonella typhi expresses various virulence antigens like H-antigens, O-antigens and Vi antigens which plays vital role in ...

While probing the vicinity of ompC, a copy of the IS200 insertion element was found between the gyrA and rcsC genes of Salmonella typhi, the causal agent of typhoid fever. This distinctive feature was conserved throughout 63 S. typhi isolates of different geographical origins and was absent from 46 other Salmonella serotypes, including those most associated with human infections, as well as fro...

The indirect fluorescent antibody test using a whole Salmonella typhi Vi suspension as the antigen has been evaluated for the diagnosis of typhoid fever. Results using sera from 140 patients with S typhi infections proved on culture show the test to have good sensitivity. The test appears to be highly specific, although it has not yet been investigated with respect to typhoid vaccination or in ...

Enteric fever is predominantly caused by Salmonella enterica serovar Typhi and Salmonella enterica serovar Paratyphi A, and accounts for an annual global incidence of 26.9 millions. In recent years, the rate of S. Paratyphi A infection has progressively increased. Currently licensed vaccines for typhoid fever, live Ty21a vaccine, Vi subunit vaccine, and Vi-conjugate vaccine, confer inadequate c...

BACKGROUND The two typhoid vaccines, the parenteral Vi capsular polysaccharide and the oral live whole-cell Salmonella Typhi Ty21a vaccine, provide similar levels of protection in field trials. Sharing no antigens, they are thought to confer protection by different mechanisms. This is the first head-to-head study to compare the humoral immune responses to these two vaccines. METHODS 50 age- a...

Two new antigenic acidic polysaccharides, Vi-P and Vi-C, were isolated from the microcapsule of Salmonella typhi by a very mild procedure. The antigens were purified to serological homogeneity, and it was found that each of them shares with Vi antigen one of its two serological determinants (a different one in each case). One of the antigens Vi-C, was also isolated from Escherichia coli B, whic...

The past decade has seen remarkable progress in our understanding of the scale global typhoid fever problem,1 alarming emergence south Asia extensively drug-resistant Salmonella enterica serovar Typhi (S Typhi) threatening effective treatment,2 and WHO prequalification a conjugate vaccine,3 new tool to prevent disease. In Lancet, Firdausi Qadri colleagues report analysis 18 months follow-up clu...