Shigella broth ISO

Shigella is the bacterium that causes the disease shigellosis, also known as bacillary dysentery. Shigella is one of the most easily transmitted bacterial diarrheas, since it can occur after fewer than 100 bacteria are ingested. Foods that come into contact with human or animal waste can transmit Shigella. Thus, handling toddlers' diapers, eating vegetables from a field contaminated with sewage, or drinking pool water are all activities that can lead to shigellosis.

Casein peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Dextrose is a source of vitamins, particularly the B-group. Bacteriological agar is the solidifying agent. Dextrose is the fermentable carbohydrate providing carbon and energy. Potassium phosphates act as a buffer system. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Polysorbate 80 is incorporated to neutralize phenols, hexachlorophene, formalin. Novobiocin is the selective agent that inhibits most of the companion flora.

Preparation

Suspend 31.5 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. AVOID OVERHEATING. DO NOT AUTOCLAVE. Dispense into appropriate containers and use on the same day.

According to ISO 21567

For the detection of Shigella spp. according to ISO 21567:

1. Prepare a 1:10 dilution of the sample in Shigella Broth with 0.5 µg of novobiocin. Homogenize and incubate in anaerobiosis at 41.5 ± 1 °C for 16-20 h.
2. Inoculate three selective agars to obtain isolated colonies: MacConkey Agar (LC-1052), XLD Agar (LC-1274) and Hektoen Agar (LC-1030). Incubate at 37 ± 1 °C for 20-24 h.
3. Biochemical and serological confirmation.

• ISO 21567:2004 Microbiology of food and animal feeding stuffs - Horizontal method for the detection of Shigella spp.
• King, S. & Metzger Appl. Microbiol. 16:577. 1968.
• King, S. & Metzger Appl. Microbiol. 16:579, 1968.