ISO16140-2 Validation of Salma One Day® for the Detection of Salmonella spp. in Food Samples

Introduction:  The use of chromogenic substrates for Salmonella detection in food samples has been described in different commercial methods. Most of the media are based on C8-esterase activity with a high selectivity, but were reported to miss some strains such as S. enteritidis Dublin, or S. enteritidis Paratyphi which express a weak enzymatic activity and/or may be stressed by selective agent.

Purpose: The objective of this study was to compare the SALMA ONE DAY^® Method to the EN/ISO/6579 standard fordetection of Salmonella in food samples.

Methods: A total of 522 samples from 6 food categories (including naturally contaminated) were tested by both methods, according to the ISO16140-2 standard. The alternative method used a single enrichment in Buffered Peptone Water (16-24h at 41.5°C) and streaking onto a new medium.

Results: The study showed the ability of this new method to detect Salmonella (n>100) and to discriminate Non-Salmonella strains. Conventional chromogenic medium or XLD demonstrated some difficulties in recovering atypical strains, such as serotypes Seftenberg or Dublin. Of the 522 food samples, 225 were found positive and 249 were negative by both methods. Relative accuracy, sensitivity, and specificity measurements, along with an interlaboratory study (n=15 labs) reported that both methods were comparable, according to the ISO16140-2 standard.

Significance:  bioMerieux has developed a new medium for the detection of Salmonella in food samples. The high specificity was achieved, thanks to the combination of esterase substrates with a specific base. SALMA ONE DAY^® method was validated according to ISO16140-2 standard and enabled a faster and easier detection of Salmonella spp. in food samples compared to the EN/ISO/6579 method.