BS EN 17716:2024

Plant biostimulants. Determination of Escherichia coli. | Status: Current

1 Scope This document gives guidance for the detection and identification of the specified microorganism Escherichia coli in technical and formulated plant biostimulants, both in liquid and solid states, and also the horizontal method for the enumeration of ß-glucuronidase-positive E. coli in plant biostimulants (both in liquid and solid states). The qualitative method described in this document is based on the detection of E. coli in a non-selective liquid medium (enrichment broth), followed by isolation on a selective agar. Other methods can be appropriate, depending on the level of detection required.

NOTE 1 For the detection of E. 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 ± 1 °C on a solid medium containing a chromogenic ingredient for detection of the enzyme ß-glucuronidase.

NOTE 2 Strains of E. coli which do not grow at 44 °C ± 1 °C and, in particular, those that are ß-glucuronidase negative, such as E. coli O157, will not be detected.

This document is applicable to the blends of fertilizing products where a blend is a mix of at least two of the following component EU fertilising products categories: Fertilizers, Liming Materials, Soil Improvers, Growing Media, Plant Biostimulants, and where the following category Plant Biostimulants is the highest % in the blend by mass or volume, or in the case of liquid form by dry mass. If Plant Biostimulants is not the highest % in the blend, the European Standard for the highest % of the blend applies. In case a blend of fertilizing products is composed of components in equal quantity or in case the component EU fertilising products used for the blend have identical formulations1, the user decides which standard to apply.