Identification of qnrE3 and qnrE4, New Transferable Quinolone Resistance qnrE Family Genes Originating from Enterobacter mori and Enterobacter asburiae, Respectively

The qnrE family was designated in 2017. To date, two qnrE alleles have been discovered that are carried by plasmids. Here, we identified a new quinolone resistance gene, qnrE3, in the chromosome of Enterobacter mori clinical isolate 08-091 in China. qnrE3 conferred decreased susceptibility to fluoroquinolones, similar to qnrE1 and qnrE2. To investigate the precise origin of qnrE1, qnrE2, and qnrE3, 79 qnrE-bearing strains producing 30 qnrE variants were retrieved from the NCBI database. Phylogenetic analysis illustrated two major clusters, QnrE(Emo) and QnrE(Eas), produced mainly by the E. mori and E. asburiae strains, respectively. Comparison of the genetic context of qnrE alleles demonstrated that qnrE3 and qnrE(Eas2) alleles presumably were captured by ISEcp1 and mobilized from the E. mori and E. asburiae strains to the E. xiangfangensis and Escherichia coli strains, respectively. qnrE(Eas2) was proposed to be named qnrE4, since it has spread to another genus. All the qnrE alleles were harbored by the Enterobacter species, except those captured by ISEcp1 and mobilized into other species of Enterobacterales. E. mori is probably the source of qnrE1 to qnrE3 alleles, and E. asburiae is the reservoir of qnrE4.

Automated summary

A new quinolone resistance gene qnrE3 was identified, providing decreased susceptibility to fluoroquinolones like qnrE1 and qnrE2. Phylogenetic analysis revealed two major clusters, with qnrE3 and qnrE(Eas2) alleles possibly captured and mobilized between different bacterial strains. The study also suggested E. mori as the probable source of qnrE1 to qnrE3 alleles, while E. asburiae serves as the reservoir for qnrE4.