Sequence type-associated variation in blood brain barrier invasion capacity among predominant Listeria monocytogenes strains in China.

Listeria monocytogenes (LM) can cause severe central nervous system infections; however, current understanding of its neuroinvasion is largely based on studies using a limited number of reference strains, leaving differences among sequence types (STs) in their capacity to invade across the blood-brain barrier (BBB) poorly defined. In this study, 12 LM isolates from China, representing ST5, ST8, ST9, and ST87, were investigated using whole-genome sequencing, an in vivo oral murine infection model, and an hCMEC/D3-based in vitro BBB model to assess virulence gene profiles, organ colonization, and BBB-associated phenotypes. Virulence gene profiling revealed strain differences in several genes potentially associated with host cell interaction and BBB-related invasion. In vivo, bacterial burdens in the liver, spleen, and cecum did not differ significantly among STs, whereas brain colonization varied markedly, with ST5 and ST8 exhibiting higher brain bacterial loads than ST9 and ST87. All infected groups showed upregulated TNF-α and IL-1β expression in brain tissue, although the magnitude of induction varied among strains. In vitro, ST5 isolates, particularly strain 122, displayed stronger adhesion to and invasion of hCMEC/D3 cells, accompanied by pronounced TEER reduction, enhanced transendothelial translocation, and disruption of tight junction proteins, whereas ST9 exhibited weaker BBB-associated phenotypes. These findings may help clarify the heterogeneity of neuroinvasive potential among prevalent LM isolates from China.