Slanetz and Bartley Medium, Granulated is recommended for detection and enumeration of faecal Streptococci by membrane filtration technique. The medium is highly selective for Enterococci. Sodium azide inhibits gram-negative organisms. Triphenyl Tetrazolium Chloride is reduced to the insoluble formazan inside the bacterial cell forming dark red-coloured colonies. Enterococcus faecalis grows luxurianlly as red or maroon colonies while Escherichia coli is inhibited on this medium.