IS1R-Mediated Plasticity of IncL/M Plasmids Leads to the Insertion of bla(OXA-48) into the Escherichia coli Chromosome

The OXA-48 carbapenemase is mainly encoded by similar to 62-kb IncL/ M plasmids. However, chromosome-mediated genes have been observed in Escherichia coli isolates. In this work, we investigated the genetic environment of OXA-48 in members of the family Enterobacteriaceae (n = 22) to understand how...

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Published in:Antimicrobial agents and chemotherapy 2014-07, Vol.58 (7), p.3785-3790
Main Authors: Beyrouthy, R., Robin, F., Delmas, J., Gibold, L., Dalmasso, G., Dabboussi, F., Hamzé, M., Bonnet, R.
Format: Article
Language:English
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Life Sciences
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Summary:The OXA-48 carbapenemase is mainly encoded by similar to 62-kb IncL/ M plasmids. However, chromosome-mediated genes have been observed in Escherichia coli isolates. In this work, we investigated the genetic environment of OXA-48 in members of the family Enterobacteriaceae (n = 22) to understand how the OXA-48-encoding gene is transferred into the E. coli chromosome. The OXA-48-encoding gene was located within intact Tn1999.2 transposons in the similar to 62-kb plasmids or within a truncated variant of Tn1999.2 for the OXA-48-encoding genes located in the chromosomes of E. coli bacteria. The analysis of the Tn1999.2 genetic environment revealed an inverted orientation of the transposon in five similar to 62-kb plasmids (5/ 14 [35%]) and in all chromosome inserts (n = 8). The sequencing of pRA35 plasmid showed that this orientation of Tn1999.2 and the acquisition of an IS1R insertion sequence generated a 21.9-kb IS1R-based composite transposon encoding OXA-48 and designated Tn6237. The sequencing of a chromosomal insert encoding OXA-48 also revealed this new transposon in the E. coli chromosome. PCR mapping showed the presence of this element in all strains harboring an OXA-48-encoding chromosomal insert. However, different insertion sites of this transposon were observed in the E. coli chromosome. Overall, these findings indicate a plasticity of the OXA-48 genetic environment mediated by IS1R insertion sequences. The insertion sequences can induce the transfer of the OXA-encoding gene into E. coli chromosomes and thereby promote its persistence and expression at low levels.
ISSN:0066-4804
1098-6596
DOI:10.1128/AAC.02669-14