Characterization of a mobilizable megaplasmid carrying multiple resistance genes from a clinical isolate of Pseudomonas aeruginosa

Li Mei; Yang Song; Dongxin Liu; Yixiao Li; Li Liu; Keyi Yu; Mengnan Jiang; Duochun Wang; Qiang Wei

doi:10.3389/fmicb.2023.1293443

Characterization of a mobilizable megaplasmid carrying multiple resistance genes from a clinical isolate of Pseudomonas aeruginosa

Front Microbiol. 2023 Nov 27:14:1293443. doi: 10.3389/fmicb.2023.1293443. eCollection 2023.

Authors

Li Mei¹, Yang Song², Dongxin Liu¹, Yixiao Li¹, Li Liu¹, Keyi Yu³, Mengnan Jiang¹, Duochun Wang³, Qiang Wei¹

Affiliations

¹ National Pathogen Resource Center, Chinese Center for Disease Control and Prevention, Beijing, China.
² Division of Infectious Disease, Key Laboratory of Surveillance and Early-Warning on Infectious Disease, Chinese Center for Disease Control and Prevention, Beijing, China.
³ National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.

Abstract

Introduction: The horizontal transfer of antibiotic resistance genes mediated by plasmids seriously hinders the effectiveness of modern medical treatment, and thus has attracted widespread attention. Additionally, the co-selection mechanism of antibiotic resistance genes (ARGs) and heavy metal resistance genes (MRGs) on mobile elements may further exacerbate the horizontal transfer of resistance genes.

Methods: In this study, a multidrug-resistant Pseudomonas aeruginosa strain, termed BJ86 (CHPC/NPRC1.4142), was isolated from a patient's sputum specimen. In vitro tests for antimicrobial susceptibility, conjugation, whole-genome sequencing, and bioinformatics analysis were used to explore the potential mechanisms of resistance and its spread.

Results and discussion: Sequencing analysis indicates that P. aeruginosa BJ86 carries an amazing 522.5 kb-length megaplasmid, pBJ86, which contained a 93.5 kb-length multiple resistance region (MRR); 18 kinds of genes were identified as ARGs in this region, including tmexCD-oprJ, bla_DIM-1, qnrVC6 that mediate resistance to multiple antibiotics and the operons mer that mediates heavy metal mercury resistance. In addition, there is also an 80 kb variable region (VR) on the plasmid pBJ86, and the genes encoding relaxase and type IV coupling protein (T4CP) were determined in this region, both of which are related to the conjugation and transfer ability of the plasmid. Bioinformatics analysis shows that many functional genes have insertion sequences and transposases on their flanks, which may have accumulated in the plasmid pBJ86 after multiple acquisition events. Conjugated transfer and in vitro tests for antimicrobial susceptibility verified the mobility and plasmid pBJ86-mediated resistance. To our knowledge, we are the first to report a mobilizable megaplasmid that simultaneously carried tmexCD-oprJ, bla_DIM-1, qnrVC6, and the operons mer and can be transferred with frequencies of 6.24 × 10^-7 transconjugants per donor cell.

Keywords: Pseudomonas aeruginosa; blaDIM−1; conjugation transfer; mer genes; mobilizable plasmid; qnrVC6; tmexCD-oprJ.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This research project was funded by the National Key R&D Program of China (2022YFC2602200), the National Science and Technology Infrastructure of China (Project No. National Pathogen Resource Center-NPRC-32), and the Natural Science Foundation of Shenzhen (JCYJ20210324130009024).