prEN ISO 9308-4

Scope

This document describes a highly specific method for the enumeration of Escherichia coli (E. coli) in water. The method is based on membrane filtration followed by culture at 44 °C on chromogenic agar medium containing an ingredient for the detection of the enzyme β-glucuronidase, and calculation of the number of target organisms in the sample[5,6,13]. Because of the high specificity of the method, this document is suitable for waters with high levels of background bacteria, such as surface waters including bathing water and wastewater provided that they contain little particulate or colloidal matter relative to the E. coli concentration. The method can be used for fresh water and, with an adaptation, for marine water. E. coli strains which do not grow at 44 °C and those that are β-glucuronidase negative, such as E. coli O157, will not be detected as E. coli by this method. This method is not applicable to the enumeration and detection of coliform bacteria other than E. coli.