Identification of plasmid-mediated tigecycline resistance <i>tet</i> (x4) and New Delhi metallo-β-lactamase (NDM) in an <i>Escherichia coli</i> isolate from Canada

Rapid spread of carbapenemase-producing Enterobacterales is a global health threat for which tigecycline is one of the few remaining therapeutic options. Resistance by <i>tet</i>(x4) is particularly worrisome, given its presence on mobile genetic elements. Here we report on a tigecycline-resistant <i>Escherichia coli</i> strain isolated from a patient returning from Pakistan. A <i>tet</i>(x4) gene was found on an IncFII plasmid isolated from an ST410 <i>E. coli</i> co-harboring NDM-5. The combination of carbapenemase and <i>tet</i>(x4) is concerning.IMPORTANCETigecycline is one of the few last-resort therapeutic options available for treating multidrug-resistant gram-negative bacterial infections, particularly of interest in carbapenemase-producing isolates. Mobile tigecycline resistance is still relatively rare, especially in North America and among clinical isolates. Here we describe the identification of a high-risk clone (<i>E. coli</i> ST410) in Canada that contains the tigecycline resistance gene <i>tet</i>(x4) on an IncFII plasmid and <i>bla</i>_NDM-5 on a separate IncFIB plasmid. Here, we highlight a rare resistance gene in combination with a carbapenemase, both of which are plasmid mediated, complicating antimicrobial treatment options.