Azide dextrose broth

Fecal streptococci use direct inoculation of 1 ml into TSB if there is turbidity, transfer into Azide dextrose broth or Azide blood agar and identify using API and/or automated identification system. 

Presumptive positives are indicated by growth at 35 °C on Azide Dextrose broth, which also allows the organisms to be counted. The production of red colonies on Slanetz and Bartley s medium at 44 °C is also indicative of faecal streptococci, and this medium is frequently used in membrane filtration systems. These media may be in either the solid or liquid form, but solid media cannot be remelted once prepared. Azide is toxic and the manufacturer s advice for the preparation of these media should be followed. It may also become explosive in the presence of certain metals and should be disposed of carefully. Azide can be destroyed safely by treatment with excess sodium nitrite. 

Presumptive test Serial dilutions of water sample are prepared and introduced in test tubes containing azide dextrose broth and incubated at 35°C 0.5°C for 24 + 2 to 48 h. Glucose fermentation by fecal streptococci causes a change in pH value of the medium and the bromocresol purple indicator color changes to yellow. 

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