Complete nucleotide sequence of a 43-kilobase genomic island associated with the multidrug resistance region of Salmonella enterica serovar typhimurium DT104 and its identification in phage type DT120 and serovar agona

This study describes the characterization of the recently described Salmone lla genomic island I (SGI1) (D. A. Boyd, G. A. Peters, L.-K. Ng, and M. R. Mulvey, FEMS Microbiol. Lett. 189:285-291, 2000), which harbors the genes a ssociated with the ACSSuT phenotype in a Canadian isolate of Salmonella ent erica serovar Typhimurium DT104. A 43-kb region has been completely sequenc ed and found to contain 44 predicted open reading frames (ORFs) which compr ised similar to 87% of the total sequence. Fifteen ORFs did not show any si gnificant homology to known gene sequences. A number of ORFs show significa nt homology to plasmid-related genes, suggesting, at least in part, a plasm id origin for the SGI1, although some with homology to phage-related genes were identified. The SGI1 was identified in a number of multidrug-resistant DT120 and S. enterica serovar Agona strains with similar antibiotic-resist ant phenotypes. The G+C content suggests a potential mosaic structure for t he SGI1 Emergence of the SGI1 in serovar Agona strains is discussed.