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

Mounia Kortebi1, Eliane Milohanic1, Gabriel Mitchell, Christine Pe ́choux, Marie- Christine Prevost, Pascale Cossart, He ́lène Bierne1*

PLoS Pathog. (2017) 13(11): e1006734

Speaker: Hsiang-Ning Chang (張翔甯)                  Time: 13:00~14:00, April. 18th, 2018

Commentator: Dr. Jenn-Wei Chen (陳振暐老師)  Place: Room 601

Abstract:

Listeria monocytogenes (L. monocytogenes) is a gram-positive, facultative anaerobic bacterium and non spore-forming bacterium. Transmission of the pathogen is via foodborne infection, and disease symptoms might include fever, diarrhea, sepsis, or meningitis. People who are most likely to be infected by L. monocytogenes are pregnant woman, older adults, and people with weakened immunity. Though the infection rate is relatively low, fatality rates can be high, while incubation period can last up to 3 months. Moreover, 1–5% of people are asymptomatic carriers and shed the pathogen into their feces. In previous study, L. monocytogenes was found to replicate in vacuoles within macrophages in severe combined immunodeficient (SCID) mice [1]. In this study, the authors wanted to study the behavior of L. monocytogens during a long-term infection in human cells. L. monocytogenes have been known to use host actin for cell-to-cell dissemination. The authors found that upon L. monocytogenes spread, the bacteria would turn off its actin polymerization machinery and change into a persistent state. Bacteria would gradually slow down the production of ActA (actin-nucleating protein) and then itself will be enclosed in lysosome-like vacuoles termed Listeria-Containing Vacuoles (LisCVs). Interestingly, the authors discovered that a subpopulation of bacteria within the vacuole were visible but could not be cultured because they have entered a viable but non-culturable (VBNC) state. In addition, these bacteria could alternate its dormant vacuole state to active motile state. These finding demonstrated a novel adaptive lifestyle of L. monocytogenes, in which the bacteria choose to be encapsulated in a vacuole as a way to persist in the host.

Reference:

1. Birmingham CL, Canadien V, Kaniuk NA, Steinberg BE, Higgins DE, Brumell JH. Listeriolysin O allows Listeria monocytogenes replication in macrophage vacuoles. Nature. 2008; 451(7176):350–4.