Genomic and Phenotypic Investigation of the Virulence Potential of Salmonella enterica Serovar Infantis Isolated in Brazil

Salmonella Infantis ( S. Infantis) is a zoonotic and globally distributed serovar. Despite its clinical relevance, information regarding its pathogenic potential is scarce. This study evaluated the pathogenic potential of S. Infantis isolated from foods, humans, and veterinary sources in Brazil between 2013 and 2018 using genomic and phenotypic approaches. A total of 80 S. Infantis genomes were screened for virulence genes and Salmonella pathogenicity islands (SPIs). Phenotypically, 25 selected strains were analyzed for analyses of biofilm formation, invasion in Caco‐2 cells, survival in human macrophages, and in vivo infection in Galleria mellonella. A total of 9 SPIs and 150 virulence genes associated with fimbrial/nonfimbrial adherence, macrophage induction, magnesium uptake, regulation, siderophores, and type three secretion systems were detected. The 25 strains tested showed strong (4%), moderate (56%) or weak (40%) biofilm formation. A 6.1 log 10 CFU/mL average rate was found for invasion in Caco‐2 and survival in U937 macrophages. In G. mellonella , 56% of the strains were highly virulent or virulent. In conclusion, S. Infantis from diverse sources in Brazil have a high pathogenic potential, evidenced by high rates of Caco‐2 invasion and intramacrophage survival, capacity to form biofilms and to cause infection in vivo that are associated with highly frequent and conserved virulence genes and SPIs.