Identification of a novel MDR plasmid co-harbouring the carbapenem resistance gene blaVIM-2 and tigecycline resistance gene cluster tmexCD1-toprJ1 in a Pseudomonas stutzeri isolate

Tigecycline and carbapenems are a few of the last-resort antimicrobial agents used to treat serious infections caused by MDR bacteria.1–3 However, the emergence of mobile tigecycline and carbapenem resistance genes reduces their clinical efficacy. In September 2021, Pseudomonas stutzeri T75 was isolated from a porcine faecal sample in Liaoning province, China using brain heart infusion (BHI) agar plates supplemented with meropenem (1 mg/L) and tigecycline (4 mg/L). Strain T75 was identified to species level by 16S rRNA sequencing. Broth microdilution tests according to CLSI revealed that P. stutzeri T75 was resistant to meropenem, tigecycline, gentamicin, ciprofloxacin, amoxicillin, ceftazidime and cefepime, but susceptible to colistin. Carbapenemase genes were screened for by a multiplex PCR assay4 and the results showed that P. stutzeri T75 was positive for the blaVIM-2 gene. Of the mobile tigecycline resistance genes, including tet(A), tet(X) variants and tmexCD1-toprJ1,5 the tmexCD1-toprJ1 gene cluster was detected. WGS was performed using both Illumina HiSeq and Oxford Nanopore MinION platforms followed by hybrid assembly using Unicycler v 0.4.3.6 The genome was annotated automatically using RAST (https://rast.nmpdr.org/) followed by manual correction. The acquired antimicrobial resistance genes (ARGs) and plasmid replicon types were identified with the CGE services (www.genomicepidemiology.org/services/). The plasmid relaxase typing was performed using MOB-typer software.7 Plasmid comparisons were visualized using Easyfig v 2.2.5.8