Novel Plasmid-Mediated <i>tet</i> (X5) Gene Conferring Resistance to Tigecycline, Eravacycline, and Omadacycline in a Clinical Acinetobacter baumannii Isolate

Abstract

A novel, plasmid-mediated, high-level tigecycline resistance <i>tet</i>(X) gene variant, <i>tet</i>(X5), was detected in a clinical <i>Acinetobacter baumannii</i> isolate from China in 2017. Tet(X5) shows 84.5% and 90.5% amino acid identity to Tet(X3) and Tet(X4), respectively, with similar binding sites and a comparable affinity for tetracyclines. The <i>tet</i>(X5)-containing plasmid could only be transferred to <i>A. baumannii</i> via electrotransformation. This report follows the recent study describing the identification of <i>tet</i>(X3) and <i>tet</i>(X4).