Tn7382, a novel composite transposon harboring bla_NDM-1 and aphA6 in Acinetobacter baumannii

Co-transfer of carbapenem and amikacin resistance might contribute to the evolution of extensively drug resistant (XDR) Acinetobacter baumannii. The current study used bioinformatic tools and an in silico approach to investigate the potential mobility of a novel composite transposon co-harboring bla_NDM-1 and aphA6.

The transposon, named here Tn7382, was recently identified in the chromosomes of two XDR A. baumannii isolates (M02 and M11) from Egypt. The draft genomes of M02 and M11 were generated by Illumina sequencing. Nucleotide homology of Tn7382 and flanking regions was analyzed using the Basic Local Alignment Search Tool.

Tn7382 is derived from Tn125 and encompasses seven open reading frames [aphA6, ISAba125 transposase-coding gene, bla_NDM-1, ble, iso, tat, cutA] enclosed by two direct copies of ISAba14. While described for the first time, Tn7382 was found in the chromosomes of five A. baumannii strains deposited in the NCBI database. Using the Artemis Comparison Tool, the potential mobility of Tn7382 was demonstrated in silico by comparative genomic analysis of two A. baumannii strains (TP1 and TP2) retrieved from the NCBI database. The transposon was acquired by TP2 at the same location as an ISAba14 element in the ancestral variant TP1 isolated from the same patient in the USA 11 days earlier.

Here, we present the characteristics of Tn7382, a composite transposon flanked by ISAba14 and harboring the aphA6 and bla_NDM-1 resistance genes. In silico analysis inferred the potential mobility of Tn7382, but experimental validation is still required.