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

Abstract

Objectives: Co-transfer of carbapenem and amikacin resistance might contribute to the evolution of extensively drug resistant (XDR) Acinetobacter baumannii. The current study is aimed at in silico investigating the potential mobility of a novel composite transposon co- harboring blaNDM-1 and aphA6 using bioinformatic tools. Methods: The transposon, named here Tn7382, was recently described 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 BLASTN tool. Results: Tn7382 is derived from Tn125 and encompasses seven orfs [aphA6, ISAba125 transposase-coding gene, blaNDM-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 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 USA 11 days earlier. Conclusions: Here, we present the characteristics of Tn7382, a composite transposon flanked by ISAba14 and harboring the aphA6 and blaNDM-1 resistance genes. In silico analysis inferred the potential mobility of Tn7382 but experimental validation is still required.