The complete sequence of Salmonella genomic island SGI1-K

Sir, Multiple antibiotic resistance in Salmonella enterica is often caused by the presence of a class 1 integron or a complex class 1 integron, which is located inside a genomic island that integrates into the chromosome at the end of the 3′-end of the thdF gene (recently renamed trmE). The first form of this island to be identified was SGI1, which was found in S. enterica serovar Typhimurium DT104,1 and until recently it was the only completely sequenced example of this island type (GenBank accession number AF261825). However, this sequence is a confusing exemplar as serovar Typhimurium carries an additional element inserted between SGI1 and the downstream yidY gene that is not found in any other serovar that has been examined to date.2 Many SGI1 variants have been reported, most of which involve the loss, gain or replacement of antibiotic resistance genes within the boundaries of the complex class 1 integron (In104 in SGI1).2 A second independently created island form, SGI2, carries the integron in a different location.3,4 However, these various forms have generally been characterized using only PCR, hybridization and limited sequencing.