Substituting Allose as the Primary Carbon Source During Enrichment Helps Improve Detection and Isolation of Lineage II Listeria monocytogenes From Food

• Published in: Journal of food protection 2023-07, Vol.86 (7), p.100104-100104, Article 100104
• Main Authors: Upham, Jacqueline P., Eisebraun, Mikaela, Fortuna, Alex, Mallo, Gustavo V.
• Format: Article
• Language: English
• Subjects: Allose; Lineage II; Listeria monocytogenes; lmo0734-lmo0739; Smoked salmon
• ISSN: 0362-028X; 1944-9097
• DOI: 10.1016/j.jfp.2023.100104

•Listeria spp. and subtypes vary in their ability to metabolize allose.•lmo0734, lmo0735, and lmo0736 are present in Listeria spp. that metabolize allose.•Enrichment with allose broth improved the detection of L. monocytogenes from salmon.•Secondary enrichment with allose broth reduced L. innocua interference.•Lineage II L. monocytogenes, but not L. innocua, can metabolize allose. Testing of foods for low levels of the human pathogen, Listeria monocytogenes (Lm), involves a selective enrichment procedure. A nonpathogenic species of Listeria, L. innocua (Li), is often present in foods and food-manufacturing environments and is an interference organism for Lm detection due to competition during enrichment. The present study investigated whether a novel enrichment strategy incorporating the sugar allose into the secondary enrichment broth (allose method) could improve the detection of Lm from foods when Li is present. First, Canadian food isolates of Listeria spp. were tested to confirm recent reports that lineage II Lm (LII-Lm), but not Li, could metabolize allose. All LII-Lm isolates (n = 81), but not Li (n = 36), possessed the allose genes lmo0734-lmo0739, and could efficiently metabolize allose. Next, smoked salmon was contaminated with mixtures of LII-Lm and Li and tested using different enrichment procedures to compare the ability to recover Lm. Allose broth was more effective than Fraser Broth, with Lm detected in 87% (74 of 85) compared to 59% (50 of 85) of the samples (P