SERO P2 SALMONELLA TYPHI

salmonella typhi

• gram negative bacteria

• rod shaped

• motile

• facultative anaerobe

• non spore forming

o antigen

• somatic cell wall antigen (used in serotyping)

h antigen

• flagellar antigen (phase 1 and phase 2 in some serotypes)

vi antigens

• capsular antigen, found in s typhi and a few others

fimbriae

• mediate attachment to intestinal epithelial cells

flagella

• promote motility, chemotaxis, and invasion of host tissues

capsule

• anti phagocytic, protects s typhi from host immune response

endotoxin

• causes fever, inflammation, septic shock in systemic infections

type 3 secretion system

• injects effector proteins into host cells to induce uptake, invasion, and survival inside macrophages

salmonella pathogenicity islands

• spi1 invasion of intestinal epithelial cells; spi2 survival and replication in macrophages

siderophores

• scavenge iron from the hist for bacterial growth

acid tolerance response

• enables survival through stomach acid to reach intestines

intracellular survival mechanisms

• prevents lysosomal killing inside macrophages

widal test

• detects antibodies (agglutinins) in patient serum against o and h antigen

• procedure: patient serum is serially diluted and mixed with standard salmonella antigens, agglutination indicates positive reaction

• single o titer >= 1:160 is significant for typhoid fever