Predicted qnr genes in genome databases. The structure of the regions surrounding predicted qnr genes (in red) is shown. Elements that might contribute to transfer of those genes are highlighted in black. The presence of putative MDR systems is also highlighted. WGS (whole genome shotgun), CG (Complete genome), Chr (Chromosome). Only those putative qnr determinants showing more than 45% identity with known plasmid-encoded QnrA or QnrB determinants were included in the analysis. The abbreviations used in the Figure are shown in Additional file 1.