Nationwide clinical–genomic epidemiology of listeriosis in Taiwan, 2018–2025: disease manifestations in relation to clonal background

Listeriosis is an uncommon but severe foodborne infection, yet nationwide data linking pathogen genomics with clinical manifestations remain limited. We analyzed 1,252 laboratory-confirmed symptomatic listeriosis cases reported through nationwide surveillance in Taiwan during 2018–2025, with whole-genome sequencing of the corresponding clinical Listeria monocytogenes isolate from every case. The average annual incidence was 6.68 cases per 1,000,000 person-years, and 30-day all-cause mortality was 11.4%. Incidence showed an age-dependent sex pattern, with higher incidence among females aged 15–44 years and a shift toward male predominance at older ages. The female excess at ages 15–44 years persisted after exclusion of documented maternal–neonatal cases (male-to-female incidence rate ratio, 0.57; 95% confidence interval, 0.36–0.89). Clonal complex 87 (CC87) was the predominant CC (35.9%), whereas CC1 and CC2 were associated with higher odds of central nervous system (CNS) infection. LIPI-4 occurred predominantly in CC87, and LIPI-4-positive isolates showed lower odds of CNS infection; however, this association could not be separated from clonal background. More broadly, most associations of pathogenicity islands, virulence genes, and their alleles with disease manifestations could not be separated from the underlying clonal backgrounds in which these markers occurred, and none of the estimable associations remained significant after CC adjustment. This nationwide clinical–genomic study characterizes the contemporary burden of listeriosis in Taiwan and highlights clonal background as essential context for interpreting associations between virulence markers and disease manifestations.