M-T 7 Agar is recommended by APHA for water testing to detect Escherichia coli and total coliforms from water by membrane filtration technique. Lactose fermenting colonies turn yellow while lactose non-fermenters turn blue to purple. Tergitol 7 and Polyoxyethylene ether inhibits gram-positive organisms. Escherichia coli, Klebsiella aerogenes, Klebsiella pneumoniae grow as yellow coloured colony on membrane while Salmonella Enteritidis develop as blue to purple coloured colony.
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