Escherichia coli O157 (H7 or H-) comprising stx genes and eae gene is a pathogenic E. coli belonging to the Shigatoxin-producing E. coli (STEC) pathogroup and may cause severe infections in humans.

Humans are usually infected through contaminated food or direct contact with animals or the environment such as contaminated water. STEC O157 may survive well in different types of foods, and the infectious dose is low.

This method describes the qualitative determination of E. coli O157 in food and animal feed. It is also applicable for primary production samples (animal fecal samples and environmental samples), although the performance of the method on this matrix is not validated.

This updated method now includes information on sorbitol-fermenting E. coli O157 (SF E. coli O157). In addition, obligatory determination of presence of the major virulence genes stx and eae by a reference laboratory has been added. It is mandatory to test isolates of E. coli O157 for the presence of stx and eae genes as E. coli O157 without virulence factors are occasionally isolated from samples. A protocol for determination of the genes is not included in the present method as this should be carried out by a reference laboratory. A new Annex 2 has been added, describing the method for analysis of samples from primary production (i.e. fecal samples and environmental samples from primary production).

NMKL 151 Presumptive Shigella spp. Detection in foods has been reintroduced and updated.

The presence of Shigella in food and the environments is normally of human fecal origin. Shigella is host-specific for higher primates, including humans. Shigella is usually present in foods in low number due to their poor ability to compete. Consequently, they are notoriously difficult to detect in foods. The infectious dose is low, and only 10-100 Shigella are needed to cause infection. Due to the low infectious dose, cross contamination from infected humans to foods and further on to more persons can occur, for example through handling of foods. Person-to-person contamination can also occur. It has been shown that Shigella can survive in weeks and months in or on different foodstuffs.

In this updated method, a step to reduce background flora and ease the isolation of Shigella for some matrices has been introduced. In addition, recommendation regarding which plates to use has been added. This method can be used for subsequent isolation of Shigella spp. after using NMKL 174, 2016, for detection of the virulence factor ipaH in enrichment broth. NMKL 174 can also be used for detection of ipaH in presumptive colonies.

NordVal International Certificate 038, "iQ-Check® Salmonella II kit", from Bio-Rad has been renewed. It is a qualitative method allowing the detection of Salmonella spp-specific DNA sequences after enrichment in buffered peptone water. It is based upon polymerase chain reaction and real time detection using fluorescent probes. NordVal International evaluated the data for the method according to NordVal International protocol No. 1 and ISO 16140-2:2016 and concludes that the method for detection of Salmonella spp. on a broad range of food, animal feed and primary production samples provides results equivalent to the results from the reference method. See the certificate here.

NordVal International Certificate 020 issued to Bio-Rad for RAPID’E.coli 2 Agar has been renewed. The method describe ready-to-use selective and chromogenic plates, which inhibits growth of Gram-positive bacteria and of the principal Gram-negative bacteria other than Enterobacteriacae. The method is applicable for detection of E. coli in a broad range of foods. See the certificate here.

NordVal International Certificate 033 issued to HyServe for Compact Dry TC Method for enumeration of total count has been extended. The method describe ready-to-use chromogenic plates. An extension study was performed to extend the method and to ensure compliance with ISO 16140-2 and NordVal Validation Protocol 1. By reviewing the results, NordVal International concludes, that the method provides results equivalent to the results from the reference method when applied for detection in a broad range of foods, pet food and environmental samples. See the certificate here.

NordVal International Certificate 039 issued to Qualicon Diagnostics for BAX® System Real-Time PCR Assay Campylobacter jejuni/coli/lari has been renewed. The method is a direct method without enrichment step and with ready to use tubes for the BAX instrument. The method is applicable for detection of Campylobacter jejuni, coli and lari in poultry faeces on cloacae swabs. See the certificate here.

NMKL method No. 202, "Methylmercury: determination by isotope dilution GC-ICPMS in foodstuffs", describes the quantitative determination of mono-methylmercury (MMHg) (10-5000 µg/kg dry weight) in mainly marine biota samples. The principle of the method is that the sample is spiked with an appropriate amount of Hg isotope-enriched MMHg and extracted. After derivatisation the sample is analysed using GC-ICPMS. The GC separates the different mercury species before MMHg is atomised and ionised in the high temperature of the ICP. The ions are extracted from the plasma, and in a mass spectrometer the ions are separated by their mass/charge ratio.

NMKL /NordVal International and AOAC International have signed an Agreement of Cooperation that will streamline the process for test kit companies seeking recognition from NordVal International and AOAC simultaneously.

The new agreement allows the two organizations and their respective certification programmes to jointly develop and use common evaluation protocols and select independent testing laboratories.

The goal of the cooperative agreement is to reduce the economic barrier imposed by requiring separate studies. Joint protocols mean method developers will be able to conduct testing once at one laboratory, and the data will be applicable to both AOAC and NMKL. Each organization will conduct reviews, render decisions on approvals of methods and issue certificates.

NordVal International receives many applications and, consequently, regularly seeks members to its technical committee. If you are interested in contributing to its work, ref. below-mentioned description of functions, please contact the NMKL secretariat. To see description of functions please click here

When the result of a chemical analysis is presented in an analytical report it is recommended that it should always be reported as a numerical result. For the result to be complete, the measurement uncertainty of the analysis should also be included. In many cases, a result can be very hard to interpret unless accompanied by its uncertainty.

In this updated version of the procedure, guidance on how to handle bias / systematic errors in relation to measurement uncertainty is included. The principles described in Nordtest TR 537 for environmental analyzes have been introduced in the NMKL procedure and examples showing how these calculations are to be performed have been added. Whether one can or should correct for systematic errors is a complex issue, and a new section has been added to explain his. Additionally, minor restructuration and update of references have been undertaken.

A scandinavian version of this 3rd edition will follow.

NMKL method No. 203 describes the determination of sodium content in foodstuffs by capillary electrophoresis (CE). The CE method is quick and needs both very little sample handling and low amount of solvents. It is applicable to various matrices such as bread, vegetables and meat products. The salt content is calculated from the sodium content with the formula: salt = 2.5 x sodium.

Sodium is extracted from sample and analysed by CE with diode array detector. The minimum content of sodium that can be detected and quantified is 0.03 g/100 g.