Genome-wide identification of novel genomic islands that contribute to Salmonella virulence in mouse systemic infection

Salmonella pathogenicity islands are inserted into the genome by horizontal gene transfer and are required for expression of full virulence. Here, we performed tRNA scanning of the genome of Salmonella enterica serovar Typhimurium and compared it with that of nonpathogenic Escherichia coli in order to identify genomic islands that contribute to Salmonella virulence. Using deletion analysis, we identified four genomic islands that are required for virulence in the mouse infection model. One of the newly identified pathogenicity islands was the pheV-tRNA-located genomic island, which is comprised of 26 126 bp, and encodes 22 putative genes, including STM3117-STM3138. We also showed that the pheV tRNA-located genomic island is widely distributed among different nontyphoid Salmonella serovars. Furthermore, genes including STM3118-STM3121 were identified as novel virulence-associated genes within the pheV-tRNA-located genomic island. These results indicate that a Salmonella-specific pheV-tRNA genomic island is involved in Salmonella pathogenesis among the nontyphoid Salmonella serovars.