Genomic surveillance reveals diverse carbapenem-resistant Pseudomonas aeruginosa in Fujian

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a major global hospital pathogen, and the emergence of difficult-to-treat resistance (DTR-PA) has further narrowed therapeutic options. Fujian Province in southeastern China has consistently reported a high burden of CRPA, yet large-scale multicenter genomic surveillance data for the region have remained limited. A new multicenter study, published in Annals of Clinical Microbiology and Antimicrobials, now provides a province-wide genomic picture of the pathogen and maps the molecular mechanisms behind its resistance.

Between June and December 2022, the researchers collected 215 non-duplicate clinical CRPA isolates from nine cities across Fujian Province. Each isolate underwent antimicrobial susceptibility testing (AST), whole-genome sequencing (WGS), and phylogenetic analysis. The combined approach allowed the team to evaluate resistance profiles, clonal distributions, and the molecular mechanisms driving carbapenem resistance simultaneously across a large, geographically diverse collection.

The susceptibility testing produced one of the study’s most striking findings: cefepime–zidebactam showed favorable in vitro activity, with all 215 isolates categorized as susceptible according to the proposed pharmacokinetic/pharmacodynamic (PK/PD) breakpoint of ≤ 32 mg/L. Polymyxin B and amikacin were the next most active agents.

Compared with carbapenem-resistant but non–difficult-to-treat Pseudomonas aeruginosa (non-DTR-PA) isolates, DTR-PA strains showed markedly higher resistance rates to ceftazidime–avibactam (52.9% vs. 7.6%) and cefepime–tazobactam (62.9% vs. 6.2%). Resistance to ceftolozane–tazobactam also rose among DTR-PA isolates, but the increase was relatively modest (37.1% vs. 15.6%), leaving that agent below 50% resistance even in the hardest-to-treat group.

Whole-genome sequencing revealed remarkable genetic diversity: 82 distinct sequence types were identified across the collection, with high-risk clones including ST235, ST277, and ST244 predominating. Phylogenomic analysis resolved six major clades, demonstrating both regional clustering within Fujian and evidence of intercity dissemination. This pattern indicates that while certain successful lineages have spread between cities, the provincial epidemic is not dominated by a single clone but rather by a mosaic of genetically distinct strains.

The resistance mechanisms uncovered by WGS were predominantly non-enzymatic. The major chromosomal carbapenem-resistance (CR) markers included OprD-related CR-markers in 69.3% of isolates, MexAB-OprM-related CR-markers in 47.4%, and AmpC-related CR-markers in 41.4%. By contrast, carbapenemase genes—enzymes that directly hydrolyze carbapenems—were detected in only 8.8% of isolates, underscoring that chromosomal mechanisms, not acquired carbapenemases, drive most resistance in this setting.

The study’s conclusions carry practical weight for treatment decisions. Cefepime–zidebactam and polymyxin B demonstrated favorable in vitro activity against the provincial collection. Notably, although resistance to ceftolozane–tazobactam was higher in DTR-PA isolates than in non-DTR-PA isolates, it remained below 50%, suggesting that it may remain a potential treatment option for selected DTR-PA infections. These are in vitro observations, and clinical outcomes would need to be confirmed in patient studies, but the susceptibility patterns provide a benchmark for empirical therapy in the region.

By combining a nine-city sampling frame, a large isolate collection, and full-genome analysis, the study fills a surveillance gap for a province that has long reported among China’s highest CRPA burdens. The picture that emerges—genetic diversity, predominance of non-enzymatic chromosomal resistance, dissemination of high-risk clones such as ST235, ST277, and ST244, and enrichment of metallo-β-lactamases in difficult-to-treat isolates—illustrates why CRPA remains one of the most formidable hospital pathogens and why continued genomic surveillance is essential for tracking its evolution.

Subject of Research: Genomic epidemiology and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa in Fujian Province, China

Article Title: Genomic epidemiology and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa in Fujian Province, China: a multicenter study

Article References: Yang, H., Xu, B., Huang, Y., Xu, X., Li, X., Xu, Y., & Li, B. (2026). Genomic epidemiology and resistance mechanisms of carbapenem-resistant Pseudomonas aeruginosa in Fujian Province, China: a multicenter study. Annals of Clinical Microbiology and Antimicrobials. https://doi.org/10.1186/s12941-026-00897-w

Image Credits: AI Generated

DOI: 10.1186/s12941-026-00897-w

Keywords: carbapenem-resistant Pseudomonas aeruginosa, DTR-PA, whole-genome sequencing, antimicrobial resistance, ST235, metallo-β-lactamase, cefepime–zidebactam, Fujian Province, nosocomial pathogen, OprD, efflux pump, multicenter surveillance