Improved Recovery of Stressed Listeria monocytogenes from Frozen Foods

Julie McLennon, Antonela Borza, Mikaela Eisebraun, Rafael A. Garduño

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The Canadian reference method for the enumeration of Listeria monocytogenes (Health Canada method MFLP-74) was modified by the addition of a layer of non-selective tryptone soy agar (TSA) to the Oxford, Palcam, and (or) Rapid’L.mono selective agars, to improve the recovery of stressed L. monocytogenes from frozen foods. The performance of the standard selective agars versus the selective agars with an additional TSA agar layer (TAL agars) showed that for each of the frozen food items tested (vegetables, shrimp and meatballs), as well as for all data combined, L. monocytogenes counts were significantly higher (up to 20% higher) in TAL agars in relation to the standard agars (p < 0.0001, α = 0.05). A selectivity assessment showed that the 50 inclusivity L. monocytogenes strains tested produced true positive reactions on the TAL agars, and the 30 exclusivity bacterial strains tested produced true negative results on the TAL agars, indicating that the specificity of the selective agars was not altered by the additional non-selective TSA layer. In light of the 2016 Listeria outbreak linked to frozen fruits and vegetables in the USA, the results of this method investigation seem to be timely and particularly important for the regulatory testing of frozen foods.

Original languageEnglish
Pages (from-to)403-414
Number of pages12
JournalFood Analytical Methods
Volume11
Issue number2
DOIs
Publication statusPublished - Feb 1 2018
Externally publishedYes

Bibliographical note

Funding Information:
Funding This work was funded by internal research grants provided by the Canadian Food Inspection Agency.

Publisher Copyright:
© 2017, Crown Copyright.

ASJC Scopus Subject Areas

  • Analytical Chemistry
  • Food Science
  • Applied Microbiology and Biotechnology
  • Safety, Risk, Reliability and Quality
  • Safety Research

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