Increased spread and replication efficiency of Listeria monocytogenes in organotypic brain-slices is related to multilocus variable number of tandem repeat analysis (MLVA) complex

Abstract

BackgroundListeria (L.) monocytogenes causes fatal infections in many species including ruminants and humans. In ruminants, rhombencephalitis is the most prevalent form of listeriosis. Using multilocus variable number tandem repeat analysis (MLVA) we recently showed that L. monocytogenes isolates from ruminant rhombencephalitis cases are distributed over three genetic complexes (designated A, B and C). However, the majority of rhombencephalitis strains and virtually all those isolated from cattle cluster in MLVA complex A, indicating that strains of this complex may have increased neurotropism and neurovirulence. The aim of this study was to investigate whether ruminant rhombencephalitis strains have an increased ability to propagate in the bovine hippocampal brain-slice model and can be discriminated from strains of other sources. For this study, forty-seven strains were selected and assayed on brain-slice cultures, a bovine macrophage cell line (BoMac) and a human colorectal adenocarcinoma cell line (Caco-2). They were isolated from ruminant rhombencephalitis cases (n = 21) and other sources including the environment, food, human neurolisteriosis cases and ruminant/human non-encephalitic infection cases (n = 26).ResultsAll but one L. monocytogenes strain replicated in brain slices, irrespectively of the source of the isolate or MLVA complex. The replication of strains from MLVA complex A was increased in hippocampal brain-slice cultures compared to complex C. Immunofluorescence revealed that microglia are the main target cells for L. monocytogenes and that strains from MLVA complex A caused larger infection foci than strains from MLVA complex C. Additionally, they caused larger plaques in BoMac cells, but not CaCo-2 cells.ConclusionsOur brain slice model data shows that all L. monocytogenes strains should be considered potentially neurovirulent. Secondly, encephalitis strains cannot be conclusively discriminated from non-encephalitis strains with the bovine organotypic brain slice model. The data indicates that MLVA complex A strains are particularly adept at establishing encephalitis possibly by virtue of their higher resistance to antibacterial defense mechanisms in microglia cells, the main target of L. monocytogenes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0454-0) contains supplementary material, which is available to authorized users.

Variable Carbon Source Utilization, Stress Resistance, and Virulence Profiles Among Listeria monocytogenes Strains Responsible for Listeriosis Outbreaks in Switzerland

“…N14-0435 and N11-1515 included as background strains belong to lineage I, serotype 1/2b and lineage II, serotype 1/2a respectively. In addition, L. monocytogenes EGDe a lineage II, serotype 1/2a strain was included in the study as a reference strain and L. innocua J5051 was included as a negative control in some of the experiments (Guldimann et al, 2015).…”

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

“…Hypovirulent clones of L. monocytogenes generally belong to lineage II (Jacquet et al, 2004;Maury et al, 2016;McLauchlin, 1990;Orsi et al, 2011), while hypervirulent clones have been predominantly found in lineage I, which is also the most prevalent lineage in animal and human infection (Chenal-Francisque et al, 2011;Jacquet et al, 2004;Kim et al, 2018;Maury et al, 2016;Orsi et al, 2011). Of those, strains belonging to sequence type (ST) 1 are particularly prevalent in CNS infection of ruminants and humans (Dreyer et al, 2016;Maury et al, 2016) and behave hyperinvasive in vitro compared to the reference strain EGD-e and other strains from lineage II (Dreyer et al, 2016;Guldimann et al, 2015;Rupp et al, 2017). Differences in genomic gene content suggest that lineage I strains harbor specific genes that may confer hyperinvasion and hypervirulence resulting in the higher prevalence of these strains in clinical infection (Dreyer et al, 2016;Maury et al, 2016).…”

“…This is particularly true for strains from specific sequence types (ST, as determined by multilocus sequence typing (MLST)), namely ST1 and 4. These two ST additionally behave hypervirulent and hyperinvasive in experimental in vivo and in vitro infections (Dreyer et al, ; Guldimann et al, ; Maury et al, ).…”

“…These two ST additionally behave hypervirulent and hyperinvasive in experimental in vivo and in vitro infections (Dreyer et al, 2016;Guldimann et al, 2015;Maury et al, 2016).…”

RECON-Dependent Inflammation in Hepatocytes Enhances Listeria monocytogenes Cell-to-Cell Spread

“…Evidence in support of this proposition is provided by studies of natural isolates of L. monocytogenes . Human clinical isolates, including epidemic strains, are more likely to exhibit enhanced spread compared to the lab reference strain 10403S and to strains from ruminants or food sources ( 50 , 51 ). The plaque sizes of these hyperspreading isolates are larger by 1.2- to 1.5-fold, which contextualizes the 1.5- to 2-fold increase in spread areas observed in RECON-deficient cells.…”