Tn125-related acquisition of blaNDM-like genes in Acinetobacter baumannii

Abstract

A multidrug-resistant Acinetobacter baumannii isolate recovered from a patient hospitalized in Switzerland after a transfer from Serbia produced the NDM-1 carbapenemase. The bla(NDM-1) gene was part of a chromosomally located Tn125 composite transposon bracketed by two copies of the same insertion sequence, ISAba125. This transposon was also associated with the acquisition and expression of the bla(NDM-2) gene in an A. baumannii isolate in Germany. Tn125 appears to be the main vehicle for dissemination of bla(NDM) genes in that species.

Fig 1

Features of transposon Tn125, carrying the bla_NDM-1 and bla_NDM-2 genes. Genes and their transcription orientations are indicated by arrows. The lengths of the target genes and the exact location of the target site are not to scale. oriIS of ISCR21 is indicated by a circle. The 3-bp Tn125 target sites identified in each isolate are underlined and uppercase. GC content is indicated in percentages. Gene names are abbreviated according to their corresponding proteins: iso for phosphoribosylanthranilate isomerase; tat for the twin-arginine translocation pathway signal sequence protein; dvt for the divalent cation tolerance protein; Δpac for truncated phospholipid acetyltransferase; rhs for the Rhs protein; orf for an unknown open reading frame; and mfs for major facilitator superfamily metabolite/H⁺ symporter. IRL and IRR indicate inverted repeat left and right, respectively.