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This part of ISO 16649 specifies a horizontal method for the enumeration of b-glucuronidase-positive Escherichia coli in products intended for human consumption or for the feeding of animals. It uses a colony-count technique after resuscitation using membranes and incubation at 44°C on a solid medium containing a chromogenic ingredient for detection of the enzyme b-glucuronidase. WARNING - Some strains of Escherichia coli may grow poorly or not at all in media incubated at 44 °C. This includes strains of E. coli O157:H7 and O157:H-. Additionally, some strains of Escherichia coli, notably those belonging to serotype O157:H7 are mostly β-glucuronidase negative. Consequently, some strains of E. coli, including pathogenic ones, will not be detected by this method.