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

TL;DR

A tigecycline-resistant E. coli strain from Canada carries tet(x4) and NDM-5, raising concerns about limited treatment options.

Contribution

First report of tet(x4) and NDM-5 co-occurring in a Canadian E. coli isolate on separate plasmids.

Findings

tet(x4) gene was found on an IncFII plasmid in E. coli ST410.

NDM-5 was identified on a separate IncFIB plasmid in the same isolate.

Combination of plasmid-mediated resistance genes complicates treatment options.

Abstract

Rapid spread of carbapenemase-producing Enterobacterales is a global health threat for which tigecycline is one of the few remaining therapeutic options. Resistance by tet(x4) is particularly worrisome, given its presence on mobile genetic elements. Here we report on a tigecycline-resistant Escherichia coli strain isolated from a patient returning from Pakistan. A tet(x4) gene was found on an IncFII plasmid isolated from an ST410 E. coli co-harboring NDM-5. The combination of carbapenemase and tet(x4) is concerning.

Tigecycline 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 (E. coli ST410) in Canada that contains the tigecycline resistance gene tet(x4) on an IncFII plasmid and blaNDM-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.

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