Modified Salt Broth is used for differentiating enterococcal group D Streptococci from nonenterococcal group D Streptococci. High salt content of this medium acts as a differential and selective agent by interefering with membrane permeability and osmotic equilibrium (1). Salt tolerant strains grow within 48 hours. Heart digest and peptic digest of animal tissue provide essential nitrogenous nutrients while dextrose is the carbohydrate source in the medium. Bromo cresol purple is the pH indicator which turns yellow from purple at acidic pH (2). Enterococcal group D Streptococcus species (Enterococcus faecalis, Enterococcus faecium, Enterococcus durans and Enterococcus avium) can be easily differentiated from the nonenterococcal species like Streptococcus bovis, Streptococcus equines, by the 6.5% sodium chloride tolerance test. Serological group D Streptococci or bile esculin positive isolate may be easily identified as an Enterococcus species.
Storage and Shelf-life:
Store below 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label.
References:
1.MacFaddin J., 1985, Media for Isolation - Cultivation - Identification - Maintenance of Medical Bacteria, Vol.I, Williams and Wilkins, Baltimore.
2.Facklam and Caney, 1985, Manual of Clinical Microbiology, 4th ed., Lennette, Balows, Hausler and Shadomy (Eds), ASM, Washington, D.C.