ISO 16649-1

Description / Abstract: This document specifies a horizontal method for the enumeration of β-glucuronidase-positive Escherichia coli by 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 β-glucuronidase[9][10][13][14][17][ 18][19][20]. It is applicable to

— products intended for human consumption,

— products intended for feeding animals,

— environmental samples in the area of food production and food handling, and

— samples from the primary production stage such as animal faeces, dust, and swabs.

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[11]. Consequently, some strains of E. coli, including pathogenic ones, will not be detected by this method. β-glucuronidase activity may also be exhibited at 44 °C by certain other members of the Enterobacteriaceae, notably Shigella[15] and Salmonella[16].