Investigating the Biological Characteristics and Pathogenic Potential of Listeria innocua Isolated from Food Through...

L. monocytogenes is a common foodborne pathogen that typically causes infections through the consumption of food contaminated with this bacterium. This study seeks to elucidate the biodiversity as well as evolutionary characteristics of L. innocua strains from different regions using comparative genomics, exploring the virulence and pathogenic potential of these strains. The findings are expected to deepen our understanding of L. innocua and provide valuable reference for public health risk assessment related to this bacterium. We performed comparative genomics on 108 food-source L. innocua isolates sourced from the USA, England, China, and Egypt to explore their biological traits and assess their pathogenic potential by predicting virulence and antibiotic resistance genes, with subsequent validation of pathogenicity through animal studies. Pan-genomic analysis showed that geographically distinct L. innocua strains possess open genomes, offering a stable genetic basis that facilitates adaptation to diverse environments. Through virulence gene prediction, we found that L. innocua strains from different regions harbor virulence genes identical to those found in pathogenic L. monocytogenes, such as inlA and inlB, as well as internal genes that may enhance the pathogenic potential of the strains. This finding demonstrates that L. innocua strains exhibit pathogenic potential. To validate their virulence, we subsequently conducted virulence assays utilizing the Galleria mellonella larval model. Following infection with L. innocua, 100% mortality was observed in a subset of Galleria mellonella larvae, albeit with a delayed time to death compared to L. monocytogenes infection. This indicates that while L. innocua exhibits attenuated virulence relative to L. monocytogenes, it retains pathogenicity. Consequently, the potential contribution of L. innocua to listeriosis cannot be overlooked in public health risk assessments. L. innocua strains isolated from food can carry virulence and resistance genes identical to those found in pathogenic L. monocytogenes strains, indicating that these L. innocua strains possess certain virulence and pathogenic potential, which was further validated through subsequent animal experimentation. This study enhances our genomic understanding of L. innocua and underscores that detecting its key virulence genes is critical for public health safety, thereby providing valuable insights into its pathogenic potential.