Pseudomonas aeruginosa in wound infections: Genomic characterization and emergence of hypervirulent ST1965/ST3418 strains co-harbouring exoU and exoS

Objective

To investigate the phenotype and genotype characteristics of Pseudomonas aeruginosa isolates from wound infections.

Methods

Seventy-six P. aeruginosa strains isolated from wound infections in a university hospital were analysed. Antimicrobial susceptibility testing, biofilm formation assays, and whole-genome sequencing were performed on all strains. The virulence of potential hypervirulent strains was assessed using a Galleria mellonella infection model.

Results

Among the 76 tested strains, 49 (64.5%) were susceptible to all tested antibiotics. The β-lactamase-encoding gene positivity rate was 57.9%, while the OprD gene mutation rate was 1.3%. All isolates were classified into 56 distinct multilocus sequence types. Serotype distribution revealed O11 (22.37%, 17/76), O16 (19.74%, 15/76), and O1 (18.42%, 14/76) as the most prevalent. The exoU gene was predominantly associated with serotype O11. Over 80% of strains harboured biofilm-related virulence genes, and all exhibited strong biofilm-forming capacity. Six exoU+/exoS+ strains (serotype O4) were identified, with ST1965 and ST3418 demonstrating potential hypervirulence in the infection model.

Conclusions

P. aeruginosa isolates from wound infections displayed sporadic genomic profiles, high antibiotic susceptibility, and robust biofilm formation. The emergence of exoU+/exoS+ hypervirulent clones (ST1965 and ST3418), characterized by enhanced virulence and biofilm production, highlights their potential to cause treatment-refractory infections and severe clinical outcomes. Continuous surveillance and tailored therapeutic approaches are imperative for managing infections caused by these clones.