Emergence of an Extensive Drug Resistant Pseudomonas aeruginosa Strain of Chicken Origin Carrying bla_IMP-45, tet(X6), and tmexCD3-toprJ3 on an Inc_pRBL16 Plasmid

This study reports an extensively drug resistant Pseudomonas aeruginosa strain PA166-2 which was of chicken origin and carrying bla_IMP-45, tet(X6) and tmexCD3-toprJ3 on a single plasmid. The strain was characterized by antimicrobial susceptibility testing, resistance gene screening, conjugation assay, whole-genome sequencing, and bioinformatics analysis. Strain PA166-2 was resistant to tigecycline and carbapenems. It belonged to ST313 and carried a plasmid pPA166-2-MDR, which belongs to the incompatibility group Inc_pRBL16. pPA166-2-MDR harbored a 78 Kb multidrug resistance (MDR) region carrying an array of antimicrobial resistance genes, including bla_IMP-45, tet(X6), and tmexCD3-toprJ3. The gene bla_IMP-45 was inserted into the backbone of plasmid pPA166-2-MDR within a class 1 integron, In786. tmexCD3-toprJ3 in plasmid pPA166-2-MDR was inserted in umuC, constituting the genetic context of ISCfr1-tnfxB3-tmexC3-tmexD3-toprJ3-ΔumuC. The genetic context of tet(X6) in this plasmid was identical to that of other reported plasmid-borne tet(X) variants, namely, tet(X6)-abh-guaA-ISVsa3. To the best of our knowledge, this is the first report of the cooccurrence of bla_IMP-45, tet (X6), and tmexCD3-toprJ3 in one plasmid in Pseudomonas sp. The emergence of plasmid-mediated tigecycline resistance genes tmexCD3-toprJ3 and tet(X6), as well as carbapenemase genes from chickens expanded the global transmission of vital resistance genes. Findings from us and from others indicate that plasmids of the incompatibility group Inc_pRBL16 may serve as a reservoir for carbapenem and tigecycline resistance determinants.