Shigella are gram-negative, non-motile, non-spore forming rod-shaped bacteria closely related to Escherichia coli and Salmonella . Shigella infection is typically via ingestion (faecal-oral contamination), depending on age and condition of the host, as few as 10 bacterial cells can be enough to cause an infection. Shigella causes dysentery that results in the destruction of the epithelial cells of the intestinal mucosa in the cecum and rectum. Some strains produce enterotoxin and Shiga toxin, similar to the verotoxin of E. coli O157:H7(1). Shigella Broth Base is used for the isolation and cultivation of Shigella species (2), as recommended by APHA (3).
Shigella Broth Base contains casein enzymic hydrolysate as a source of carbon, nitrogen, vitamins and minerals. Dextrose provides the necessary carbohydrates. Buffering action in the medium is provided by dipotassium hydrogen phosphate and potassium dihydrogen phosphate. Sodium chloride maintains the osmotic balance of the medium. Polysorbate 80 is inhibitory for growth of accompanying microflora besides providing growth factors. Novobiocin is inhibitory for gram-positive bacteria such as S. aureus and certain gram-negative organisms such as H. influenzae and some species of Proteus.
Directions: Suspend 31.5 grams in 1000 ml distilled water. Heat if necessary to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool medium to 45-50°C and add rehydrated content of 1 vial of Shigella Selective Supplement (FD108) under aseptic conditions. Mix well and dispense in sterile test tubes.