Gang Hu,1,* Wei Yan,2,* Fenfen Dong,2 Gang Li,3 Xiaoxing Zhang,1 Qiongshan Li,1 Peng Zhang,2 Lei Ji2 

1Department of Obstetrics, Huzhou Maternity & Child Health Care Hospital, Zhejiang, People’s Republic of China; 2Department of Microbiology Testing, Huzhou Center for Disease Control and Prevention, Zhejiang, People’s Republic of China; 3Department of Clinical Laboratory, Huzhou Maternity & Child Health Care Hospital, Zhejiang, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Lei Ji, Huzhou Center for Disease Control and Prevention, Huzhou, Zhejiang, 313000, People’s Republic of China, Email jileichn@163.com

Background: Listeriosis, a severe foodborne infection caused by Listeria monocytogenes, poses significant risks during pregnancy, including maternal–neonatal transmission. This study describes the clinical and genomic characteristics of an sequence type 8 (ST8) L. monocytogenes strain involved in maternal–neonatal transmission during pregnancy.
Methods: Clinical presentation, diagnostic process, and treatment outcomes of the case were documented in detail. Whole-genome sequencing (WGS) and subsequent genomic analyses were performed on L. monocytogenes isolates obtained from the maternal and neonatal blood cultures.
Results: A 33-week pregnant woman presented with decreased fetal movements and underwent an emergency cesarean delivery. Postpartum, she developed a high fever, and blood cultures from both the mother and the neonate the day after caesarean delivery confirmed L. monocytogenes infection. WGS revealed that the isolates belonged to serotype 1/2a, ST8, clonal complex (CC) 8, and lineage II. Both isolates exhibited susceptibility to first-line antibiotics, including penicillin and ampicillin, and contained virulence and stress adaptation genes such as LIPI-1 and SSI-1. Phylogenetic analysis based on cg-SNP linked the clinical isolates to foodborne ST8 strains from Huzhou and Shanghai, suggesting potential contamination routes.
Conclusion: This case highlights the importance of timely diagnosis and effective antibiotic management in preventing adverse pregnancy outcomes. It also underscores the need for enhanced food safety surveillance and genomic monitoring of L. monocytogenes to better understand the transmission dynamics and to avoid the extension of a foodborne infection.

Keywords: Listeria monocytogenes, maternal–fetal transmission, whole-genome sequencing, ST8, antimicrobial susceptibility