First reported Pseudomonas soli bloodstream infection confirmed by whole-genome sequencing after MALDI-TOF misidentification.

OBJECTIVE

To determine the species identity of a rare environmental Pseudomonas isolate recovered from blood culture and to evaluate its antimicrobial resistance profile and pathogenic potential.

METHODS

The isolate PS1 was characterized by MALDI-TOF MS identification, antimicrobial susceptibility testing, and whole-genome sequencing. Species assignment was established using average nucleotide identity (ANI) analysis and core-genome phylogenetic analysis. Virulence- and resistance-associated genes were annotated using multiple databases. Phenotypic validation was performed through biofilm formation, serum killing, chrome azurol S (CAS) iron acquisition assay, and the Galleria mellonella infection model.

RESULTS

MALDI-TOF MS misidentified PS1 as Pseudomonas putida, whereas WGS confirmed it as P. soli, showing an ANI value of 99.0536% with P. soli ASM49897v2. PS1 was resistant to some β-lactams and trimethoprim-sulfamethoxazole, but remained generally susceptible to carbapenems, aminoglycosides, and quinolones. Genomic analysis identified virulence-associated modules involved in alginate biosynthesis, iron acquisition, secretion systems, and surface structure remodeling. Phenotypic assays demonstrated that PS1 had strong biofilm-forming ability (OD₅₇₀ = 0.210 ± 0.042) and iron acquisition capacity (CAS halo diameter, 8.63 ± 0.38 mm), showed a certain degree of survival in normal human serum, and exhibited dose-dependent lethality in the Galleria mellonella model.

CONCLUSION

This study reports the first case of bloodstream infection caused by P. soli confirmed by whole-genome sequencing. PS1 harbored multiple virulence‑related genetic modules and exhibited corresponding pathogenic phenotypes. These findings support that P. soli may have opportunistic pathogenic potential.