First characterization of four repeat regions with the blaNDM-1 carried on an IncFII plasmid in Enterobacter hormaechei

Carbapenem-resistant Enterobacteriaceae (CRE) have emerged as a critical threat to global health, and multicopy resistance genes are a potential contributor to increased resistance. This study investigates a novel arrangement of four <i>bla</i> _NDM-1 genes in tandem on an IncFII plasmid from <i>Enterobacter hormaechei</i>. Whole-genome sequencing (WGS) of <i>E. hormaechei</i> isolates L710hy identified a four-tandem repeat of the <i>bla</i> _NDM-1 gene, with each copy's environment nearly identical (IS<i>CR1</i>-<i>aph(3')-VI</i>-IS<i>Aba125</i>-<i>bla</i> _NDM-1-<i>ble</i>-<i>iso</i>-<i>tat</i>-<i>dsbD</i>-<i>cutA</i>-<i>sul1</i>-IS<i>CR1</i>). The study suggests a correlation between the <i>bla</i> _NDM-1 copy number and minimum inhibitory concentration (MIC) values for carbapenems, though further research is needed to confirm this correlation. The stability of these four <i>bla</i> _NDM-1 tandem repeat structures was also investigated. This is the first documented case of <i>bla</i> _NDM-1 tandem repeats in <i>E. hormaechei</i>, and the IS<i>CR1</i> and other insertion sequence may play a role in this arrangement.