Virulence-Associated Genomic Architecture of Canine Otitis Externa-Derived Pseudomonas aeruginosa Isolates from Hungary

Background: Canine otitis externa is a clinically relevant niche where Pseudomonas aeruginosa may persist under inflammatory, antimicrobial, and biofilm-favoring conditions. This study characterized the virulome and population structure of canine otitis externa-derived P. aeruginosa isolates from Hungary. Methods: Of 110 isolates previously subjected to minimum inhibitory concentration testing, 70 phenotypically selected isolates underwent long-read whole-genome sequencing and were included in virulence-factor analysis. Virulence-associated genes were detected using the Virulence Factor Database with an 80% identity and 80% coverage threshold and were interpreted by functional systems, including motility, adhesion, biofilm formation, secretion systems, siderophores, quorum sensing, secreted enzymes, and type III secretion system effectors. Results: The isolates carried a broad and highly conserved virulence-associated backbone. Genes related to alginate production, type IV pili, flagellar motility, pyochelin, phenazine biosynthesis, Xcp secretion, type VI secretion, and proteolytic enzymes were widely distributed. Type III secretion effector genes were variable: exoT was detected in 68/70 isolates, exoY in 63/70, exoS in 50/70, and exoU in 15/70. MLST indicated a genetically diverse population, and virulome size showed no strong correlation with the modified multiple antimicrobial resistance index. Conclusions: These findings support integrated genomic surveillance of virulence and antimicrobial resistance in canine otitis-associated P. aeruginosa.