A review of the International Organization for Standardization (ISO) guidelines for the detection of Salmonella from faeces

Abstract

Adherence to the guidelines of The International Organization for Standardization (ISO) for the isolation of Salmonella from faeces is important to laboratory personnel, researchers and epidemiologists to ensure effective diagnosis, maximal recovery and high sensitivity/specificity of laboratory tests. The aim of this study is to review the ISO guidelines for the detection of Salmonella from faeces using standards published by ISO and other internationally recognized bodies. The ISO 6579 of 2002 described the process for the detection of Salmonella in faeces. About 25g of faecal samples is collected, mixed together and specimen taken from different parts to ensure maximum recovery of the organism. Processes for the identification of the organism were prescribed by the standard. In the amendment made to ISO 6579 (Annex D) it was recommended that Modified Semisolid Rappaport Vasiliadis (MSRV) be used as selective enrichment medium. Further amendment made to this standard was in 2007 where clause 4 described non-selective pre-enrichment, selective enrichment, use of 2 selective solid media and biochemical tests as the 4 stages of the isolation of Salmonella in faeces. The amendment of ISO 6579 in 2017 combined the guidelines for the isolation of Salmonella species, S. Typhi/Paratyphi from milk/milk-products and faeces. It proposed the use of selenite cysteine broth in addition to Rappaport Vasiliadis (RVS) and Muller-Kauffmann Tetrathionate-Novobiocin (MkTTn) and BSA in addition to Xylose Lysine Deoxycholate (XLD) Agar for the isolation of S. typhi and paratyphi. It recommended the performance of methyl-red, Simmoncitrate, H 2 S, motility and urease biochemical tests, deleted Vogues Proskaer test while indole and β-Galactosidase (ONPG) tests were made optional. This standard has evolved over the years to ensure efficient recovery of Salmonella from faeces based on real-time result and feedback received by the organization from laboratories all over the world.