Prevalence, genomic diversity, and invasion potential of Listeria monocytogenes in ready-to-eat seafood products distributed in Japan.

Authors

Ayaka Nakamura, Kaori Komori, Yuna Kono, Ayaka Hara, Takashi Kuda, Hajime Takahashi

Published in

International journal of food microbiology. Volume 460. Pages 111958. Jul 10, 2026. Epub Jul 10, 2026.

Abstract

Listeria monocytogenes is a major foodborne pathogen capable of persisting and growing under refrigerated storage, raising food safety concerns for ready-to-eat (RTE) foods. This study investigated the occurrence, genetic and invasion characteristics of L. monocytogenes in five categories of RTE seafood products distributed in Japan: cod roe, seasoned cod roe, salmon roe, smoked salmon, and minced tuna. A total of 500 retail samples, comprising 100 samples per category, were examined in 2023. L. monocytogenes was detected most frequently in minced tuna (23%), followed by salmon roe (9%), seasoned cod roe (4%), cod roe (2%), and smoked salmon (2%). Quantification using a three-tube MPN method indicated generally low contamination levels, with most positive samples containing <10 MPN/g. However, physicochemical analyses of pH and water activity suggested that most products were capable of supporting the growth of L. monocytogenes during storage. Whole-genome sequencing of 40 isolates revealed substantial genomic diversity, classifying isolates into 14 clonal complexes and 27 cgMLST types, with no marked bias toward either BIGSdb-defined Lineage I or II. Gene content analysis identified stress survival islets, disinfectant tolerance-associated determinants, and virulence-associated loci, including LIPI-3 and LIPI-4, in specific clonal backgrounds. Epithelial invasion assays revealed wide variation in invasion phenotypes, with higher invasion among Lineage I isolates and near-zero invasion in isolates carrying premature stop codons in inlA. Overall, these findings highlight heterogeneous risk profiles among L. monocytogenes contaminating RTE seafood products in Japan.

PMID:
42447553
Bibliographic data and abstract were imported from PubMed on 15 Jul 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.