All laboratories except one that took part in a proficiency test to detect Salmonella in flaxseed performed well, according to the Dutch National Institute for Public Health and the Environment (RIVM).

A total of 42 National Reference Laboratories (NRLs) for Salmonella participated, 37 from 28 EU member states and five from other countries. The European Union Reference Laboratory (EURL) for Salmonella is held by RIVM.

Flaxseed is used as a food product and an ingredient in animal feed. The objective was to test the performance of participating labs in detecting different concentrations of Salmonella Typhimurium in flaxseed samples from the Netherlands. This is important to verify examination of samples is done uniformly in all EU member states and comparable results are obtained.

Labs used an internationally accepted method to detect Salmonella in samples. Each lab received 18 samples each containing 25-grams of flaxseed, which were artificially contaminated with two different concentrations of Salmonella Typhimurium or did not contain Salmonella. Flaxseed samples were artificially contaminated at the EURL-Salmonella lab.

They consisted of six negative samples, six with a low level of Salmonella Typhimurium (inoculum 10 colony forming units (cfu)/samples) and six with a high level (105 cfu/sample). The labs also had to test two control samples: a procedure control and a positive control with Salmonella.

The method for detection of Salmonella spp. was EN ISO 6579-1:2017 and participants were asked to report Salmonella detected or not detected for each sample after confirmation. Thirteen labs also used a second detection method for analyzing the flaxseed samples with similar results.

Reporting issues
All participating NRLs for Salmonella were able to detect low- and high-level concentrations of Salmonella.

Forty-one labs detected Salmonella in all contaminated flaxseed samples with a low level of Salmonella Typhimurium. One lab detected Salmonella in five of six contaminated flaxseed samples with a low level of the pathogen. This is still above the criteria of at least three positive samples for a good performance.

All labs did not detect Salmonella in the negative samples and found it in all contaminated samples with a high level of Salmonella Typhimurium.

One lab originally reported one negative sample as positive. However, this was an issue from software to result form which was confirmed by raw data showing the sample tested negative.

Another lab swapped results of the control samples when reporting so scored a moderate performance. The lab detected Salmonella in the procedure control, while it was not detected in their own positive control sample.

This lab made a mistake when entering results for the two control samples and switched them on the result form. This was confirmed by raw data and no further actions were considered necessary, according to the report.

The EURL-Salmonella workshop 2020 is planned in Zaandam, the Netherlands for May 28 and 29. A proficiency test on detection of Salmonella in mussels is being organized this month with a deadline in April.

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