CSN P CEN/TS 17715 This document provides a method for verifying that the pathogen Shigella spp. is not present in microbial plant biostimulants in a concentration that exceeds the respective limits outlined in the EU Regulation on Fertilising Products. The detection method for Shigella pathogens is not sensitive and quantification is rarely performed. Detection is usually performed using an enrichment medium followed by subculturing onto a variety of selective media. Original English text of CSN EN Standard. The price of the Standard included all amendments and correcturs.