Genomic Relationship Between High-Risk Pseudomonas aeruginosa Clone ST244 Serotypes O5 and O12 from Southeastern Brazil

Pseudomonas aeruginosa is an opportunistic pathogen commonly associated with nosocomial infections and environmental dissemination. Among its high-risk clones, ST244 is notable for its global distribution and distinctive genomic traits. This study reports whole-genome sequencing of ten ST244 isolates from hospitalized patients and wastewater in a healthcare complex in Southeastern Brazil. Genomic comparisons revealed a highly conserved clonal group, with nine isolates forming a tight monophyletic cluster based on rMLST, SNP phylogeny, and average nucleotide identity (>99.5%). One isolate showed close phylogenetic proximity to strains from Asia and North America, suggesting international dissemination. Serotype analysis revealed both O5 and O12 variants, indicating intra-lineage antigenic diversity. Resistance profiling identified multidrug-resistant phenotypes carrying carbapenemase genes (blaOXA-494, blaOXA-396) and diverse insertion sequences (ISPa1, ISPa6, ISPa22, ISPa32, and ISPa37), facilitating horizontal gene transfer. Virulence gene analysis showed conserved elements related to adhesion, iron uptake, secretion systems, and quorum sensing, while the cytotoxin gene exoU was absent. These results highlight clonal persistence, possible intra-hospital transmission, and links to globally circulating ST244 sublineages. Our findings underscore the importance of genomic surveillance to track high-risk P. aeruginosa clones at the clinical–environmental interface.