This document is applicable to fertilizing products, which are classified as PFC 1(A) and PFC 1(B) or the PFC 1(A) and PFC 1(B) component in PFC 7 of Regulation (EU) 2019/1009 [1]. However, the present method was not validated for blends. This document specifies a colony-count technique at 44 °C on a solid medium containing a chromogenic ingredient for the detection of the enzyme β-glucuronidase. The method is based on ISO 16649-2 [4]. Strains of Escherichia coli which do not grow at 44 °C and, in particular, those that are β-glucuronidase negative, such as Escherichia coli O157, will not be detected. Detected microorganisms are presumptively determined β-glucuronidase-positive Escherichia coli, since some Enterobacteriaceae, in particular Shigella and Salmonella, can also show β-glucuronidase activity at 44 °C.