Emergence of an Extensive Drug Resistant Pseudomonas aeruginosa Strain of Chicken Origin Carrying blaIMP-45, tet(X6), and tmexCD3- toprJ3 on an IncpRBL16 Plasmid

Abstract

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-△umuC. 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. IMPORTANCE Pseudomonas aeruginosa is an opportunistic pathogen that causes infections that are difficult to treat. This study reported, for the first time, the occurrence of last-resort antibiotic resistance determinants bla_IMP-45, tet(X6), and tmexCD3-toprJ3 on a single plasmid in P. aeruginosa from chickens. The P. aeruginosa strain belonged to ST313 and was resistant to last-line antibiotics, namely, carbapenems and tigecycline. The plasmid carrying the last-line resistance genes belonged to the incompatibility group Inc_pRBL16, which was reported to contain different profiles of accessory modules and thus carried diverse collections of resistance genes. 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. The results in this study highlighted that Inc_pRBL16 plasmids may serve as a reservoir for the dissemination of resistance genes. Control measures should be implemented to prevent the further dissemination of such strains.

Keywords: Pseudomonas aeruginosa; blaIMP-45; extensive drug resistance; tet(X6); tmexCD3-toprJ3.

FIG 1

Detailed information regarding plasmid pPA166-2-MDR from Pseudomonas aeruginosa carrying an MDR region that encodes bla_IMP-45, tet(X6) and tmexCD3-toprJ3. (A) Comparative structural analysis of pPA166-2-MDR with other similar plasmids available in the NCBI nr database. The outermost circle represents the reference plasmid pPA166-2-MDR. The MDR region is highlighted with dotted lines. The acquired antimicrobial resistance genes, namely, conserved Inc_pRBL16 backbone markers repA_IncpRBL16 together with its iterons, parB2-parA, che, pil, and ter are annotated. (B) Alignment of the 78,304 bp MDR region in plasmid pPA166-2-MDR with the similar region in plasmid pR31014-IMP. Red, cyan, and orange arrows denote antimicrobial resistance genes, mobile elements, and other protein-encoding genes, respectively. Alignment of genetic contexts of tmexCD3-toprJ3 (C) and tet(X6) (D) in plasmid pPA166-2-MDR with similar sequences. Red, cyan, and orange arrows denote antimicrobial resistance genes, mobile elements, and other protein-encoding genes, respectively. The Δ symbol indicates that the gene is truncated.