AUTHOR=Poimenidou Sofia V. , Dalmasso Marion , Papadimitriou Konstantinos , Fox Edward M. , Skandamis Panagiotis N. , Jordan Kieran 

TITLE=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

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01103

DOI=10.3389/fmicb.2018.01103

ISSN=1664-302X

ABSTRACT=<p>The <italic>prfA</italic>-virulence gene cluster (<italic>p</italic>VGC) is the main pathogenicity island in <italic>Listeria monocytogenes</italic>, comprising the <italic>prfA, plcA, hly, mpl, actA</italic>, and <italic>plcB</italic> genes. In this study, the <italic>p</italic>VGC of 36 <italic>L. monocytogenes</italic> 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 <italic>prfA</italic> and <italic>hly</italic>, with the lowest nucleotide diversity (π) among all genes (<italic>P</italic> &lt; 0.05), and the lowest number of alleles, substitutions and non-synonymous substitutions for <italic>prfA</italic>. Conversely, the most diverse gene was <italic>actA</italic>, which presented the highest number of alleles (<italic>n</italic> = 20) and showed the highest nucleotide diversity. Grouping by serotype had a significantly lower π value (<italic>P</italic> &lt; 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 <italic>hly</italic> and <italic>mpl</italic> 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 <italic>hly</italic> gene, where serotype 4b Irish strains were distinct from Greek and Australian strains. Australian strains showed less diversity in <italic>plcB</italic> and <italic>mpl</italic> relative to Irish or Greek strains. Notable differences regarding sequence mutations were identified between food-associated and clinical isolates in <italic>prfA, actA</italic>, and <italic>plcB</italic> 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.</p>