Emergence of a Multidrug-Resistant Enterobacter hormaechei Clinical Isolate from Egypt Co-Harboring mcr-9 and blaVIM-4

Abstract

<b>A</b><b>bstract</b><b>:</b> This study describes the first full genomic sequence of an <i>mcr-9</i> and <i>bla</i>_VIM-4-carrying multidrug-resistant <i>Enterobacter hormaechei</i> clinical isolate from Egypt. The strain was isolated in April 2015 from the sputum of a patient in Cairo, Egypt. The <i>mcr-9</i> and <i>bla</i>_VIM-4 genes were identified by PCR screening and DNA sequencing; the isolate was subjected to antimicrobial susceptibility testing, conjugation experiments, and whole genomic sequencing. <i>mcr-9</i> and <i>bla</i>_VIM-4 were carried by an IncHI2 plasmid, pAMS-38a (281,121 bp in size); the plasmid also carried genes conferring resistance against sulfonamides (<i>sul1</i>), quinolones (<i>qnrA1</i>), trimethoprim (<i>dfrA1</i>), β-lactams (<i>bla</i>_TEM-1B), aminoglycosides (<i>aac (6')-II</i>, <i>aadA23</i>, <i>aadA2b</i>, and <i>ant(2'')-Ia</i>). The strain was susceptible to colistin (MIC, <0.25 μg/mL); this could be due to the absence of the <i>qseC</i>/<i>qseB</i> regulatory system located downstream of <i>mcr-9</i> in Enterobacterales, which is involved in the induction of colistin-resistance. The genetic context of <i>mcr-9</i> and <i>bla</i>_VIM-4 was identified as IS<i>1</i>-<i>mcr-9</i>-IS<i>903</i>-<i>pcoS-∆pcoE-rcnA</i> and <i>intI1</i>-<i>bla</i>_VIM-4_-<i>aac (6')-II</i>-<i>dfrA1</i>-<i>∆aadA23</i>-<i>smr</i>-IS<i>Pa21</i>-<i>qacE∆1</i>, respectively. This is the first report of an <i>mcr-9</i> and <i>bla</i>_VIM-4 /IncHI2-carrying multidrug-resistant <i>E. hormaechei</i> clinical isolate from Africa and the Middle East. Plasmids of the IncHI2 group and the two insertion sequences (IS<i>1</i>, and IS<i>903</i>) might be the main vehicles for dissemination of <i>mcr-9</i>. Further screening for <i>mcr-9</i> is essential for identifying its incidence and to prevent its dissemination.