Shigella and Salmonella

Genus Shigella Genus Salmonella

Shigella

Gram negative bacilli Non motile non capsulated

Shigella colonies are pale (colourless)
Shigella colonies are colourless with no black center

Salmonella

Gram negative bacilli Motile non-sporing

Bismuth Sulfite Agar

Black or Brown colonies with metallic sheen
Bismuth sulfite Brilliant green


Bile salt Lactose Sodium thiosulfate Neutral Red indicator
colourless colonies with black center
Salmonella – Shigella Agar

Selenite Broth

Is a selective – enrichment medium designed to increase the number of Salmonella and inhibits the growth of other M.O.

Triple Sugar Iron Agar (TSI)

The ability of an organism to attack sugars. The production of gas. Formation of H2S.
pink (K) yellow (A) Black colour due to H2S production

Triple Sugar Iron Agar (TSI)

1%Lactose ,1%Sucrose ,0.1% Glucose. Sodium thiosulfate Ferrous Sulfate (Feso4). Phenol red indicator. H2s + Feso4 Fes + H2so4 (Black precipitate) TSI: K/A (shigella) TSI:K/A ,H2S+ (Salmonella)