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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Microbiol. | doi: 10.3389/fmicb.2019.01644

The novel internalins InlP1 and InlP4 and the internalin-like protein InlP3 enhance the pathogenicity of Listeria monocytogenes

 Eva Harter1, Caroline Lassnig2, Eva M. Wagner1, 3, Andreas Zaiser1,  Martin Wagner1, 3 and  Kathrin Rychli1*
  • 1Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Austria
  • 2Institut für Tierzucht und Genetik, Veterinärmedizinische Universität Wien, Austria
  • 3Österreichisches Kompetenzzentrum für Futter- und Lebensmittelqualität, Sicherheit und Innovation, Austria

The pathogenicity of the human foodborne pathogen Listeria (L.) monocytogenes relies on virulence factors such as internalins. In 2009/2010 two L. monocytogenes strains were responsible for a serious listeriosis outbreak in Austria, Germany and the Czech Republic. One of these clones, QOC1, which caused 14 cases including five fatalities, encodes the novel internalins inlP1, inlPq and inlP4 and the novel internalin-like protein inlP3 in the genomic region of hypervariable genetic hotspot 9 in addition to the standard set of virulence genes.
The in silico prevalence study revealed that these genes rarely occur in L. monocytogenes and mainly in minor clonal complexes.
To obtain first insights of the role of these genes in the pathogenicity of L. monocytogenes, we studied the gene expression under conditions mimicking the ingestion in the host. Expression of inlP1, inlP3, inlPq and inlP4 was increased under gastric stress and in intracellular bacteria grown in intestinal epithelial cells. Furthermore, colonization of the liver and the spleen was slightly, but significantly reduced 72 hours post infection in an oral mouse infection model when inlP1 or inlP4 was deleted. Moreover, the impact of InlP1 and InlP3 in virulence was shown in vitro in human intestinal epithelial cells.
In this study we conclusively demonstrate a potential contribution of uncommon novel internalins and an internalin-like protein to the pathogenicity of L. monocytogenes.

Keywords: Listeria moncytogenes, outbreak strain, accessory genome, Internalin, internalin-like protein, Virulence

Received: 15 Mar 2019; Accepted: 03 Jul 2019.

Edited by:

David Rodriguez-Lazaro, University of Burgos, Spain

Reviewed by:

Arun K. Bhunia, Purdue University, United States
Javier Pizarro-Cerda, Institut Pasteur, France  

Copyright: © 2019 Harter, Lassnig, Wagner, Zaiser, Wagner and Rychli. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Kathrin Rychli, Institute for Milk Hygiene, University of Veterinary Medicine Vienna, Vienna, 1210, Austria, kathrin.rychli@vetmeduni.ac.at