Whole-genome sequencing reveals molecular characterization of carbapenem-resistant Pseudomonas aeruginosa clinical isolates from a third-tier general hospital in southwest China.

OBJECTIVE

To characterize the molecular characteristics of carbapenem-resistant Pseudomonas aeruginosa (CRPA) from a third-tier general hospital in southwest China.

METHODS

A total of 106 non-duplicate clinical isolates of CRPA were collected from January 2019 to December 2023 at Science City Hospital in Sichuan Province, China. Antimicrobial susceptibility testing was performed to characterize the resistance profiles of the isolates. Whole-genome sequencing (WGS) was conducted to comprehensively characterize the sequence types (STs), virulence factors, and resistance genes. Pulsed-field gel electrophoresis (PFGE) was employed to analyze DNA fingerprinting patterns, clarifying the clonal relatedness among strains and tracing potential clonal dissemination.

RESULTS

Antimicrobial susceptibility testing demonstrated that all 106 CRPA isolates were resistant to imipenem. Consistent resistance to cefazolin and cefotetan were observed in 103 isolates. ST640 was identified as the predominant type, along with two novel STs, designated ST4440 and ST4513. Molecular characterization revealed that all isolates carried the efflux pump genes (mexA, mexB), the blaPDC (AmpC enzyme) gene and blaOXA-50, while metallo-β-lactamase genes were detected in only two isolates. All 106 isolates carried virulence gene exoT, with exoY and exoS detected in 98.1% and 91.5%, respectively. PFGE results showed that no predominant clone was observed at the 85% similarity level, suggesting that the isolates were mainly from sporadic infections.

CONCLUSION

Resistance in CRPA isolates is predominantly mediated by efflux pumps and AmpC enzymes, along with the presence of the blaOXA-50. The observed high genetic diversity underscores the need for enhanced infection control measures.