Abstract:[Objective] To investigate the role of Salmonella genomic islands of unknown functions for pathogenicity and also to identify new islands associated with Salmonella virulence. [Methods] Using Salmonella enteric serovar Typhimurium (S. Typhimurium) ATCC 14028 as wild-type strain, we constructed mutants for seven islands of unknown functions (STM14_0667?0673, 2682?2687, 2885?2891, 3721?3728, 4247?4253, 4823?4828, 5331?5341) by employing the λ Red recombinase method. Through invasion assays, macrophage replication assays, and mice experiment, we compared the virulence of the mutant strains to that of the wild-type 14028. [Results] Compared with wild-type strain, Δ2682?2687 and Δ5331?5341 significantly decreased their invasion ability to epithelial cells (P<0.01); Δ2682?2687, Δ2885?2891 and Δ5331?5341 significantly decreased their replication ability in macrophages, and also showed decreased virulence to mice, with the bacterial counts of mutants in intestine, liver and spleen were less abundant than that of the wild-type strain (P<0.05). No significant differences in invasion ability, replication ability, and virulent to mice were observed between wild-type strain and the other four mutant strains (Δ0667?0673, Δ3721?3728, Δ4247?4253 and Δ4823?4828). [Conclusions] This study found three islands of unknown functions contributing to S. Typhimurium pathogenicity, and provided powerful tools for the further research on the regulatory systems and functions of these islands.
