| Summary: | Listeriosis is one of the most notable foodborne diseases and is characterized by high rates of mortality. <i>L. monocytogenes</i> is the main cause of human listeriosis outbreaks, however, there are isolated cases of disease caused by other species of the genus <i>Listeria</i>. The aim of this study was to evaluate strains of <i>L. monocytogenes</i> (<i>n</i> = 7), <i>L. innocua</i> (<i>n</i> = 6), and <i>L. welshimeri</i> (<i>n</i> = 2) isolated from fish and shrimps for their virulence based on the presence of virulence genes and the in vivo <i>Danio rerio</i> (zebrafish) larvae models. A total of 15 strains were analyzed. The zebrafish larvae model showed that the larvae injected with <i>L. monocytogenes</i> strains were characterized by the lowest survival rate (46.5%), followed by <i>L. innocua</i> strains (64.2%) and <i>L. welshimeri</i> (83.0%) strains. Multiplex PCRs were used for detection of selected virulence genes (<i>lux</i>S, <i>act</i>A2, <i>prf</i>A, <i>inl</i>B, <i>rrn, iap</i>, <i>sig</i>B, <i>plc</i>B, <i>act</i>A, <i>hly</i>A), the majority of which were present in <i>L. monocytogenes</i>. Only a few virulence-related genes were found in <i>L. welshimeri</i>, however, no correlation between the occurrence of these genes and larval survival was confirmed. This research highlights the importance of the potential impact that <i>Listeria</i> spp. strains isolated from fish and shrimps may have on consumers.
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