Purpose: This study aimed to assess the performance of the SalmoPresto PE system for the direct detection of Salmonella in egg-products during enrichment. The selectivity, sensitivity, and relative detection level of the method were assessed according to the ISO 16140-2:2016 standard.
Methods: The SalmoPresto PE protocol consisted of diluting a 25g sample in 225mL pre-warmed buffered-peptone-water (BPW) supplemented with novobiocin (10mg/L) and incubating it for 16-20h at 37°C. A 10µL aliquot of the enriched sample was taken from the bag and diluted into 990µL of a selective broth directly into the detection kit. Then, the kit is inserted into an optical reader (MonoPresto) which delivered a reading within 10 hours (for negative results). For the purpose of this study, the SalmoPresto RT250 protocol was compared to the ISO6579 reference method in an unpaired study design. A total of 100 Salmonella strains and 30 non-Salmonella strains were analysed to assess the specificity. To assess the relative trueness, 62 egg-product samples were analysed; while 30 samples, with different contamination levels including a fractional positive contamination level, were analysed to assess the relative limit of detection (RLOD).
Results: The SalmoPresto PE method detected all the Salmonella strains tested and showed cross reaction with a few Citrobacter diversus strains. The trueness and RLOD results fulfilled the acceptance criteria, showing that the method is sensitive and reliable.
Significance: The SalmoPresto PE method offers a new type of detection method, which provided a reliable result in less than 24 hours, with a very easy to use protocol and limited technician time.