An 11-year multicentre clinical and genomic surveillance of listeriosis across Japan.

OBJECTIVES

We conducted a multicenter retrospective study to characterize the clinical features of listeriosis and the genomic characteristics of causative Listeria monocytogenes isolates across Japan.

METHODS

In this retrospective observational cohort study, we enrolled all microbiologically confirmed listeriosis cases between Jan 1, 2011, and Dec 31, 2021. We collected the causative isolates and performed whole genome sequencing. The isolates were compared using Multi-locus Sequence Typing (MLST), core-genome MLST, and single-nucleotide polymorphism (SNP)-based phylogeny.

RESULTS

A total of 195 listeriosis cases from 22 hospitals were enrolled, including 134 cases of bacteremia, 43 cases of neurolisteriosis, 11 cases of perinatal infection, and 7 cases of other infections. Of the neurolisteriosis cases in patients aged one month to under 50 years, five out of six (83%) occurred in immunocompetent individuals. Nosocomial-onset cases accounted for 31 (17%) of the non-perinatal listeriosis cases, including four cases that presented with febrile neutropenia. Ninety-five L. monocytogenes isolates from 16 hospitals were collected, and cgMLST analysis revealed multiple previously unnoticed disease clusters. In MLST analysis, clonal complex (CC) 1 was the most predominant, followed by CC3, CC87, CC155, and CC2. International transmission events in the late 20th century contributed to the emergence of CC87 isolates in Eastern Asian countries.

CONCLUSION

This study highlighted concerns regarding neurolisteriosis occurring in immunocompetent children and young adults, as well as the significance of non-clustered nosocomial onset listeriosis. Genomic analysis using whole-genome sequencing revealed previously unnoticed disease clusters and the unique population structure of L. monocytogenes in Japan.