Evaluation of the virulence characteristics of ST11 Salmonella enterica from different sources using a 2D cell model

This study aimed to evaluate the virulence characteristics of ST11 Salmonella enterica from various sources and explore its pathogenic mechanisms and the molecular basis of antimicrobial resistance. In total, 20 Salmonella isolates collected between 2017 and 2022 from environmental, animal, clinical, and food sources were analyzed. Comprehensive investigations were conducted using whole-genome sequencing, bioinformatic analysis, broth microdilution methods, a two-dimensional (2D) cell model (Caco-2 cells), and a Galleria mellonella infection model. All tested ST11 strains carried major pathogenicity islands (PAIs) SPI-1salmonella pathogenicity island-1 (SPI-1) to SPI-5, and 90 % of the isolates harbored three or more plasmids, facilitating the horizontal transfer of virulence genes. Expression levels of sopA, ssaV, sipA/sspA, and sipB/sspB virulence genes varied significantly among strains, with sipB/sspB playing a key role in the invasion of ST11 strains. The results of invasion assays using the 2D cell model were consistent with those from the Galleria mellonella infection model, validating the 2D model's effectiveness in evaluating Salmonella's virulence. The findings suggest that Salmonella's virulence is not directly associated with the source of the isolates, and plasmid diversity may impact adaptability and transmission patterns. This study provides new insights into the pathogenic mechanisms of ST11 Salmonella and lays the groundwork for developing a novel 3D cell model to assess bacterial virulence.