Virulence of B. typhosus and resistance to o antibody

Abstract

IN previous work on the bactericidal action of serum (Felix and Olitzki, 1926) it has been shown that strains of B. typhosus and B. paratyphosus A which lare highly sensitive to 0 agglutinins are also highly susceptible to the bactericidal action of serum. Strains of this type are killed by normal sera so easily that they cannot be used a t all in bactericidal tests with inactivated and complemented immune sera. This correlation is quite consistent with the theory that bactericidal action and 0 agglutination are due to the same 0 antibody.From this observation it seemed justifiable to assume that strains of B. typhosus of the sensitive type are less virulent than non-sensitive or inagglutinable strains, which are resistant to the action of the 0 antibody. To test this hypothesis the mouse was selected as experimental animal since Grinnell (1932) and Perry, Findlay and Bensted (1933 a and b) have shown that entirely regular results are obtained when mice are used for virulence tests with B. typhosus. Xelection of sensitive and non-sensitive strains.It is now generally recognised that the " inagglutinable " or " hypo-agglutinable " cultures of B. typhosus, which are often met with amongst cultures freshly isolated from the blood of typhoid patients, are " apparent " 0 variants (Felix 1924). They are readily agglutinated by anti-0 sera and on subculture on moist agar soon develop abundant flagella and consequently are agglutinated to full titre by anti-H sera. This " inagglutinability," therefore, is an evanescent phenomenon, due to the temporary suppression of flagella and H antigen. True 0 variants, permanently non-motile and devoid of H antigen, have not yet been found amongst freshly isolated cultures of B. typhosus.There exist, however, between different strains of B. typhosus striking differences in agglutinability by 0 agglutinins, which have not yet attracted much attention. Weil and Felix (1920) first described such differences. The strain B. typhosus 901, outstanding for its remarkable agglutinability, was then recommended as a specially sensitive reagent for 0 agglutinins and is now being used in the 409

Host adapted serotypes of Salmonella enterica

“…The expression of a capsular polysaccharide, the Vi antigen, appears to be crucial for Typhi to survive in mouse and human macrophage cell lines and to resist to lysis by serum complement [65][66][67], whereas it does not appear to be necessary for epithelial cell invasion [68]. This antigen is also known to be associated with the virulence of the organism in i o and to confer immunity against typhoid fever, when injected alone, in areas with a high incidence of this disease [69,70]. This virulence factor is not uniquely found in Typhi but also in Paratyphi C and rarely, in Dublin and Citrobacter freundii, suggesting that horizontal gene transfer have occurred in the evolution of these bacteria [15,[71][72][73].…”

Vi Antigen Biosynthesis inSalmonella typhi: Characterization of UDP-N-acetylglucosamine C-6 Dehydrogenase (TviB) and UDP-N-acetylglucosaminuronic Acid C-4 Epimerase (TviC)

“…The filtrate was analyzed by HPLC equipped with a Dionex CarboPac PA-1 (4 × 250 mm) column. The product was eluted by a gradient of water as solvent A and 1 M NH 4 OAc as solvent B where the gradient ran from 20 to 25% B over 2 min, 25 to 35% B over 35 min, 35 to 100% B over 5 min, followed by 20 min wash by 100% B. The flow rate was 0.6 mL/min, and the detector was set at 267 nm.…”

SPI-7: Salmonella’s Vi-Encoding Pathogenicity Island

“…The Vi capsule polysaccharide was first identified as being associated with virulence in mice, and as an antigen distinct from that of O or H antigens [18,19]. Structurally, it is a polymer of Nacetylaminohexuronic acid [20].…”