Mobilization of the Salmonella genomic island SGI1 and the Proteus genomic island PGI1 by the A/C2 plasmid carrying blaTEM-24 harboured by various clinical species of Enterobacteriaceae

Abstract

Objectives: The objective of this study was to transfer the Salmonella genomic islands (GIs) SGI1 and SGI1-V and the Proteus GI PGI1-PmESC to clinical isolates of Enterobacteriaceae harbouring an A/C2 plasmid. Methods: The entire genetic structures of SGI1 and PGI1-PmESC from Salmonella Typhimurium and Proteus mirabilis, respectively, were characterized by PCR and DNA sequencing. Ten enterobacterial isolates from different species carrying blaTEM-24 on an A/C2 plasmid were used for the mobilization of SGI1: Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Proteus mirabilis, Enterobacter aerogenes, Citrobacter freundii, Klebsiella oxytoca, Proteus vulgaris, Providencia stuartii and Serratia marcescens. SGI1-V and PGI1-PmESC were transferred to E. aerogenes. Conjugation attempts were also performed using the wild strain E. aerogenes BOL and E. coli K-12 with or without pA/C2. Detection and location of the GI in the transconjugants were assessed by PCR targeting their junctions. Results: The multidrug resistance region of PGI1-PmESC contained a class 1 integron (aadB and aadA2) and regions deriving from transposon Tn501 and a hybrid Tn502/Tn5053 transposon, whereas SGI1 harboured the known determinants responsible for the pentaresistance. The transfer of SGI1 occurred from Salmonella Typhimurium to the 10 enterobacterial isolates, and transfer of SGI1-V and PGI1-PmESC occurred from P. mirabilis to E. aerogenes. In all transconjugants the GI was located at the 3'-end of trmE. SGI1 was also transferred to E. aerogenes BOL (pA/C2) and E. coli K-12 (pA/C2), but not to E. aerogenes BOL and E. coli K-12. Conclusions: This is the first known description of SGI1 mobilization into a broad range of enterobacterial species harbouring an A/C2 plasmid and the first demonstration of PGI1 movement. The A/C2 plasmid is responsible for the GI mobilization.