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Foodborne Pathogens: Hygiene and Safety

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Front. Microbiol. | doi: 10.3389/fmicb.2018.01103

Virulence gene sequencing highlights similarities and differences in sequences in Listeria monocytogenes serotype 1/2a and 4b strains of clinical and food origin from 3 different geographic locations.

  • 1Agricultural University of Athens, Greece
  • 2Teagasc Food Research Centre, Moorepark, Ireland
  • 3CSIRO, Australia

The prfA-virulence gene cluster (pVGC) is the main pathogenicity island in Listeria monocytogenes, comprising the prfA, plcA, hly, mpl, actA and plcB genes. In this study, the pVGC of 36 L. monocytogenes isolates with respect to different serotypes (1/2a or 4b), geographical origin (Australia, Greece or Ireland) and isolation source (food-associated or clinical) was characterized. The most conserved genes were prfA and hly, with the lowest nucleotide diversity (π) among all genes (P < 0.05), and the lowest number of alleles, substitutions and non-synonymous substitutions for prfA. Conversely, the most diverse gene was actA, which presented the highest number of alleles (n = 20) and showed the highest nucleotide diversity. Grouping by serotype had a significantly lower π value (P < 0.0001) compared to isolation source or geographical origin, suggesting a distinct and well-defined unit compared to other groupings. Among all tested genes, only hly and mpl were those with lower nucleotide diversity in 1/2a serotype than 4b serotype, reflecting a high within-1/2a serotype divergence compared to 4b serotype. Geographical divergence was noted with respect to the hly gene, where serotype 4b Irish strains were distinct from Greek and Australian strains. Australian strains showed less diversity in plcB and mpl relative to Irish or Greek strains. Notable differences regarding sequence mutations were identified between food-associated and clinical isolates in prfA, actA and plcB sequences. Overall, these results indicate that virulence genes follow different evolutionary pathways, which are affected by a strain's origin and serotype and may influence virulence and/or epidemiological dominance of certain subgroups.

Keywords: Listeria monocytogenes, Virulence, Gene sequencing, diversity, PrfA, hly, ACTA

Received: 06 Sep 2017; Accepted: 08 May 2018.

Edited by:

Maria Schirone, Università di Teramo, Italy

Reviewed by:

Arun K. Bhunia, Purdue University, United States
Valentina Bernini, Università degli Studi di Parma, Italy
Hongxia Wang, University of Alabama at Birmingham, United States  

Copyright: © 2018 Poimenidou, Dalmasso, Papadimitriou, Fox, Skandamis and Jordan. 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 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: Prof. Panagiotis Skandamis, Agricultural University of Athens, Athens, Greece, pskan@aua.gr