Listeria monocytogenes switches from dissemination to persistence by adopting a vacuolar lifestyle in epithelial cells

Abstract

Listeria monocytogenes causes listeriosis, a foodborne disease that poses serious risks to fetuses, newborns and immunocompromised adults. This intracellular bacterial pathogen proliferates in the host cytosol and exploits the host actin polymerization machinery to spread from cell-to-cell and disseminate in the host. Here, we report that during several days of infection in human hepatocytes or trophoblast cells, L. monocytogenes switches from this active motile lifestyle to a stage of persistence in vacuoles. Upon intercellular spread, bacteria gradually stopped producing the actin-nucleating protein ActA and became trapped in lysosome-like vacuoles termed Listeria-Containing Vacuoles (LisCVs). Subpopulations of bacteria resisted degradation in LisCVs and entered a slow/non-replicative state. During the subculture of host cells harboring LisCVs, bacteria showed a capacity to cycle between the vacuolar and the actin-based motility stages. When ActA was absent, such as in ΔactA mutants, vacuolar bacteria parasitized host cells in the so-called “viable but non-culturable” state (VBNC), preventing their detection by conventional colony counting methods. The exposure of infected cells to high doses of gentamicin did not trigger the formation of LisCVs, but selected for vacuolar and VBNC bacteria. Together, these results reveal the ability of L. monocytogenes to enter a persistent state in a subset of epithelial cells, which may favor the asymptomatic carriage of this pathogen, lengthen the incubation period of listeriosis, and promote bacterial survival during antibiotic therapy.

Functional characterization ofRalstonia insidiosa, a bona fide resident at the maternal-fetal interface

“…In some cases, multiple R. insidiosa rods existed within a single vacuole. These vacuoles were reminiscent of Listeria monocytogenescontaining vacuoles recently reported by Kortebi and colleagues 46 (Figure 3…”

“…In this report, we show that R. insidiosa replicates within human placental samples, human BP explants cultured ex vivo, and EVT-like JEG-3 cells in culture. Further, intracellular R. insidiosa bacteria were found in single-membrane bound compartments that closely resembled Spacious Listeriacontaining vacuoles (SLAPs) 60 or Listeria-containing vacuoles (LisCVs) 46 . Using JEG-3 cells, Kortebi et al, showed that L. monocytogenes persist in LisCVs, which are a unique, acidic vacuolar compartments that are not degradative 46 .…”

“…insidiosa within clusters or individually within each vacuolar compartment. We speculate that R. insidiosa may also utilize similar non-degradative compartments to adopt a "quiescent lifestyle" 46 within EVTs. Consistent with this, we found R. insidiosa is not harmful to EVTs as it does not induce responses associated with pathogenicityincluding cell death or heightened pro-inflammatory responses.…”

Targeting host epigenetic machinery: TheListeriaparadigm

“…On entry into an adjacent cell, bacteria escape to the cytosol from the newly formed double-membrane vacuole using LLO and the phosphatidylcholinespecific phospholipase C, perpetuating the infectious process and disseminating through the host (Pizarro-Cerda, Kuhbacher, & Cossart, 2012). In addition to this motile cytosolic life, in certain cell types, L. monocytogenes adopts another lifestyle by entering a quiescent state in vacuoles, which could promote long-term intracellular persistence (Birmingham et al, 2008;Kortebi et al, 2017).…”

Celebrating the career and legacy of Professor Pascale Cossart

“…Listeria monocytogenes is reported in all textbooks as an intracellular pathogen that replicates in the cytosol of human cells after its escape from the vacuole. However, recently this paradigm was challenged by observations that L. monocytogenes can also adopt a vacuolar lifestyle when persisting within cells (Kortebi et al, ). As another example, Mycobacterium tuberculosis, which was thought for a long time to be a strictly intravacuolar pathogen, was recently shown to rupture the phagosome and to contact the cytosol of the phagocytes it infects (Russell, ; Simeone, Bottai, & Brosch, ).…”