Co-existence of two novel phosphoethanolamine transferase gene variants in Aeromonas jandaei from retail fish

•Co-existence of two novel phosphoethanolamine transferase (eptA) gene variants in Aeromonas.•Each eptA variant confers high-level resistance to colistin in Aeromonas.•No mobile element was found in the flanking regions of eptAv7 and eptAv3. Two novel phosphoethanolamine transferase genes, eptAv7 and eptAv3, were identified in the chromosome of an Aeromonas jandaei isolate from retail fish. The variants showed 79.9% and 80.0% amino acid identity to MCR-7.1 and MCR-3.1, respectively, and increased colistin resistance 128- to 256-fold in Aeromonas salmonicida. The two variants with no mobile genetic element in the flanking regions were also observed in other Aeromonas species. This finding supports the view that Aeromonas is a reservoir for MCR-3 and MCR-7 mobile colistin resistance.