This document gives general guidelines for the detection and identification of the specified microorganism Escherichia coli in technical and formulated biostimulant products, both in liquid and solid state, and also the horizontal method for the enumeration of ß-glucuronidase-positive Escherichia coli in plant biostimulants products (both in liquid and solid state).
The qualitative method described in this document is based on the detection of Escherichia coli in a non-selective liquid medium (enrichment broth), followed by isolation on a selective agar medium. Other methods can be appropriate, depending on the level of detection required.
NOTE For the detection of Escherichia coli, subcultures can be performed on non-selective culture media followed by suitable identification steps (e.g. using identification kits).
The quantitative method described in this document uses a colony-count technique at 44 °C on a solid medium containing a chromogenic ingredient for detection of the enzyme ß-glucuronidase.
WARNING — Strains of Escherichia coli which do not grow at 44 °C and, in particular, those that are ß glucuronidase negative, such as Escherichia coli O157, will not be detected.