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Antimicrobial Agents and Chemotherapy, October 2008, p. 3745-3754, Vol. 52, No. 10
0066-4804/08/$08.00+0     doi:10.1128/AAC.00525-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Novel Insertion Sequence- and Transposon-Mediated Genetic Rearrangements in Genomic Island SGI1 of Salmonella enterica Serovar Kentucky{triangledown}

Benoît Doublet,1,2* Karine Praud,2 Sophie Bertrand,3 Jean-Marc Collard,3 François-Xavier Weill,1 and Axel Cloeckaert2

Institut Pasteur, Centre National de Référence des Salmonella, Laboratoire des Bactéries Pathogènes Entériques, 28 Rue du Docteur Roux, 75724 Paris Cedex 15, France,1 INRA, UR1282, Infectiologie Animale et Santé Publique, IASP, Nouzilly F-37380, France,2 National Reference Centre for Salmonella and Shigella, Bacteriology Division, Scientific Institute of Public Health, 14 Wytsman Street, B-1050 Brussels, Belgium3

Received 23 April 2008/ Returned for modification 3 July 2008/ Accepted 24 July 2008

Salmonella genomic island 1 (SGI1) is an integrative mobilizable element that harbors a multidrug resistance (MDR) gene cluster. Since its identification in epidemic Salmonella enterica serovar Typhimurium DT104 strains, variant SGI1 MDR gene clusters conferring different MDR phenotypes have been identified in several S. enterica serovars and classified as SGI1-A to -O. A study was undertaken to characterize SGI1 from serovar Kentucky strains isolated from travelers returning from Africa. Several strains tested were found to contain the partially characterized variant SGI1-K, recently described in a serovar Kentucky strain isolated in Australia. This variant contained only one cassette array, aac(3)-Id-aadA7, and an adjacent mercury resistance module. Here, the uncharacterized part of SGI1-K was sequenced. Downstream of the mer module similar to that found in Tn21, a mosaic genetic structure was found, comprising (i) part of Tn1721 containing the tetracycline resistance genes tetR and tet(A); (ii) part of Tn5393 containing the streptomycin resistance genes strAB, IS1133, and a truncated tnpR gene; and (iii) a Tn3-like region containing the tnpR gene and the β-lactamase blaTEM-1 gene flanked by two IS26 elements in opposite orientations. The rightmost IS26 element was shown to be inserted into the S044 open reading frame of the SGI1 backbone. This variant MDR region was named SGI1-K1 according to the previously described variant SGI1-K. Other SGI1-K MDR regions due to different IS26 locations, inversion, and partial deletions were characterized and named SGI1-K2 to -K5. Two new SGI1 variants named SGI1-P1 and -P2 contained only the Tn3-like region comprising the β-lactamase blaTEM-1 gene flanked by the two IS26 elements inserted into the SGI1 backbone. Three other new variants harbored only one IS26 element inserted in place of the MDR region of SGI1 and were named SGI1-Q1 to -Q3. Thus, in serovar Kentucky, the SGI1 MDR region undergoes recombinational and insertional events of transposon and insertion sequences, resulting in a higher diversity of MDR gene clusters than previously reported and consequently a higher diversity of MDR phenotypes.

* Corresponding author. Mailing address: Centre National de Référence des Salmonella, Laboratoire des Bactéries Pathogènes Entériques, Institut Pasteur, 28 Rue du Docteur Roux, 75724 Paris Cedex 15, France. Phone: 33-(0)1 45 68 83 44. Fax: 33-(0)1 45 68 88 37. E-mail: Benoit.Doublet{at}tours.inra.fr

{triangledown} Published ahead of print on 1 August 2008.

Antimicrobial Agents and Chemotherapy, October 2008, p. 3745-3754, Vol. 52, No. 10
0066-4804/08/$08.00+0     doi:10.1128/AAC.00525-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Doublet, B., Chu, C., Chiu, C.-H., Fan, Y.-C., Cloeckaert, A. (2009). Truncated tni Module Adjacent to the Complex Integron of Salmonella Genomic Island 1 in Salmonella enterica Serovar Virchow. Antimicrob. Agents Chemother. 53: 824-827 [Abstract] [Full Text]  
  • Doublet, B., Praud, K., Weill, F.-X., Cloeckaert, A. (2009). Association of IS26-composite transposons and complex In4-type integrons generates novel multidrug resistance loci in Salmonella genomic island 1. J Antimicrob Chemother 63: 282-289 [Abstract] [Full Text]  


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