Abstract
<jats:named-content content-type="genus-species">Listeria innocua</jats:named-content> is considered a nonpathogenic <jats:italic>Listeria</jats:italic> species. Natural atypical hemolytic <jats:named-content content-type="genus-species">L. innocua</jats:named-content> isolates have been reported but have not been characterized in detail. Here, we report the genomic and functional characterization of representative isolates from the two known natural hemolytic <jats:named-content content-type="genus-species">L. innocua</jats:named-content> clades. Whole-genome sequencing confirmed the presence of <jats:italic>Listeria</jats:italic> pathogenicity islands (LIPI) characteristic of <jats:named-content content-type="genus-species">Listeria monocytogenes</jats:named-content> species. Functional assays showed that LIPI-1 and <jats:italic>inlA</jats:italic> genes are transcribed, and the corresponding gene products are expressed and functional. Using <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic> assays, we show that atypical hemolytic <jats:named-content content-type="genus-species">L. innocua</jats:named-content> is virulent, can actively cross the intestinal epithelium, and spreads systemically to the liver and spleen, albeit to a lesser degree than the reference <jats:named-content content-type="genus-species">L. monocytogenes</jats:named-content> EGDe strain. Although human exposure to hemolytic <jats:named-content content-type="genus-species">L. innocua</jats:named-content> is likely rare, these findings are important for food safety and public health. The presence of virulence traits in some <jats:named-content content-type="genus-species">L. innocua</jats:named-content> clades supports the existence of a common virulent ancestor of <jats:named-content content-type="genus-species">L. monocytogenes</jats:named-content> and <jats:named-content content-type="genus-species">L. innocua</jats:named-content>.
Moura, Alexandra