Testing Limitations

Limitations related to the testing of Salmonella and Listeria using Solus ELISA kits.

SALMONELLA

As reported in the EN ISO 16140 validation for the Solus Salmonella ELISA method for the detection of Salmonella spp. in food and feed products –salmonella testing

  • Salmonella arizonae (CIP 5523 and CIP 5522) gave negative result even after a subculture in BHI broth at 37°C.These strains are uncommon and are usually associated with reptiles.
  •  One strain (Salmonella Gallinarum Ad 300) gave negative results when testing the whole protocol of the alternative method (subculture in RVS broth at 41.5°C), but the strain was detected after a subculture in BHI broth at 37°C. It is commonly recognized that Salmonella Gallinarum strains have difficulties being recovered at 41.5°C.


LISTERIA

As reported in the EN ISO 16140 validation for the Solus Listeria ELISA method for the detection of Listeria spp. in food products and environmental samples –

 Listeria grayi strains (Ad 1198 and Ad 1443) gave negative results whatever the inoculation level and the tested enrichment conditions (with or without adding milk in the Half Fraser broth). Only a few typical colonies were observed on OAA plates for the reference method. It is commonly recognized that this species is difficult to recover, even with the ISO method.

This strain is shown to produce negative results with other techniques (including molecular). It is rarely found in food or similar products and is not known to cause problems with human health. 

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