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J Antimicrob Chemother. 2009 Feb;63(2):282-9. doi: 10.1093/jac/dkn500. Epub 2008 Dec 11.

Association of IS26-composite transposons and complex In4-type integrons generates novel multidrug resistance loci in Salmonella genomic island 1.

Author information

1
Institut Pasteur, Centre National de Référence des Salmonella, Laboratoire des Bactéries Pathogènes Entériques, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France. benoit.doublet@tours.inra.fr

Abstract

OBJECTIVES:

Clinical isolates of Salmonella enterica serovar Haifa and Newport, which displayed extended multidrug resistance phenotypes, were investigated for the presence of Salmonella genomic island 1 (SGI1) and the genetic organization of its antibiotic resistance gene clusters.

METHODS:

The S. enterica strains were isolated from humans in France in 2003 and 2004. Antibiotic susceptibility tests and various molecular techniques were used for detection and characterization of SGI1.

RESULTS:

We identified SGI1 integrated in the 3' end of the chromosomal thdF gene in six multidrug-resistant serovar Haifa and Newport strains. Two strains, of serovar Haifa and Newport, harboured the previously described SGI1-H variant. A new variant of the novel SGI1-Ks group, named SGI1-K6, revealed IS26-mediated rearrangements of the antibiotic resistance gene cluster in two serovar Newport strains. Two other serovar Newport strains harboured the SGI1-L complex class 1 integron containing the dfrA15 and bla(PSE-1) resistance gene cassettes. In addition, these variants of SGI1 also contained large IS26-composite transposons inserted by a transposition event in the SGI1 backbone. These IS26-composite transposons showed a similar genetic structure to the SGI1-K variants containing an In4-type integron, a mercury resistance operon and parts of Tn1721 and Tn5393. These extended resistance gene clusters containing up to 10 antibiotic resistance genes were named SGI1-L1 and -L2.

CONCLUSIONS:

The serovar Haifa represents the 16th S. enterica serovar in which SGI1 has been identified. The genomic island SGI1 appears to be a hotspot of acquisition of antibiotic resistance genes by the transposition of In4-type integrons and large IS26-composite transposons.

PMID:
19074421
DOI:
10.1093/jac/dkn500
[Indexed for MEDLINE]

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