Hyperinvasiveness of Listeria monocytogenes sequence type 1 is independent of lineage I‐specific genes encoding internalin‐like proteins

Abstract

Listeriosis is a severe disease caused by the opportunistic bacterial pathogen Listeria monocytogenes ( L. monocytogenes ). Previous studies indicate that of the four phylogenetical lineages known, lineage I strains are significantly more prevalent in clinical infections than in the environment. Among lineage 1, sequence type (ST1) belongs to the most frequent genotypes in clinical infections and behaves hyperinvasive in experimental in vitro infections compared to lineage II strains suggesting that yet uncharacterized virulence genes contribute to high virulence of certain lineage I strains. This study investigated the effect of four specific lineage I genes encoding surface proteins with internalin‐like structures on cellular infection. CNS derived cell lines (fetal bovine brain cells, human microglia cells) and non‐CNS derived cell lines (bovine macrophage cells, human adenocarcinoma cells) that represent the various target cells of L. monocytogenes were infected with the parental ST1 strain and deletion mutants of the four genes. Despite their association with lineage I, deletion of the four genes investigated did not dampen the hyperinvasiveness of the ST1 strain. Similarly, these genes did not contribute to the intracellular survival and intercellular spread of L. monocytogenes ST1, indicating that these genes may have other functions, either during the infection process or outside the host.

Listeria monocytogenes at the interface between ruminants and humans: A comparative pathology and pathogenesis review

“…13,79,132,221,251 Although genomic comparisons identified putative CC-specific neurovirulence factors, 4,13 their role in hypervirulence was not confirmed. 122,254 Thus, strain-related Lm neurovirulence factors in ruminants require further exploration.…”

Environmental dissemination of pathogenic Listeria monocytogenes in flowing surface waters in Switzerland

“…Following survival within the gastrointestinal (GI) tract, multiple virulence factors (VFs) enable L. monocytogenes to invade and survive within mammalian host cells 7 . Key VFs include InlA and InlB, which belong to a family of internalins that allow the bacteria to incorporate within vacuoles of the host cells, listeriolysin O (LLO) and phospholipases PlcA and PlcB which are involved in vacuolar lysis, as well as ActA, which provides motility within the cytosol 1 , 8 , 9 .…”

Validation of Predicted Virulence Factors in Listeria monocytogenes Identified Using Comparative Genomics

“…The authors speculate that increased invasion of Δ inlC2 mutant might be due to elevated production of InlA [48]. This discrepancy between the results may be due to strain differences that lead to difference in protein structure and function or may be due to differences in the cell line type [49,50]. Antibodies to InlC2 are generated in various animal hosts infected with L. monocytogenes , indicating that InlC2 may be induced in vivo [51].…”