Study maps resistance in canine Pseudomonas otitis isolates
Bottom line
A new study in Veterinary Sciences examined archived Pseudomonas aeruginosa isolates from dogs with otitis externa in Hungary, pairing broth microdilution susceptibility testing with long-read whole-genome sequencing to better connect what the organism does in the lab with the resistance genes it carries. The authors analyzed 110 clinical isolates phenotypically and sequenced 59 matched genomes, finding reduced susceptibility across several clinically important drug classes, especially fluoroquinolones and aminoglycosides, alongside a mix of intrinsic and acquired resistance mechanisms. Among the notable findings, the fluoroquinolone-associated determinant crpP appeared in 37 of 59 genomes, sometimes on plasmid-predicted contigs, and mobile genetic element analysis suggested at least some resistance traits may be positioned for movement between strains. (mdpi.com)
Why it matters: For veterinary teams managing chronic, painful, and often treatment-refractory ear disease, the study reinforces that P. aeruginosa otitis can’t be understood through genotype or phenotype alone. Prior reviews have shown that Pseudomonas in canine otitis often persists through biofilm formation and can show substantial antimicrobial tolerance, which helps explain why empiric therapy may fail even when a familiar resistance gene pattern isn’t obvious. For clinicians, that supports culture and susceptibility testing, careful topical drug selection, and attention to stewardship when repeat cases present after prior fluoroquinolone or aminoglycoside exposure. (pmc.ncbi.nlm.nih.gov)
What to watch: The next step is whether follow-on studies tie these resistance and mobile-element findings to treatment history, clinical outcomes, and possible One Health transmission patterns in companion-animal settings. (mdpi.com)
Key facts
- Study journal
- Veterinary Sciences
- Pathogen
- Pseudomonas aeruginosa
- Condition
- Canine otitis externa
- Study location
- Hungary
- Isolates tested phenotypically
- 110 clinical isolates
- Genomes sequenced
- 59 matched genomes
- Collection years
- 2010 and 2017
- Key resistance concern
- Reduced susceptibility to fluoroquinolones and aminoglycosides
- Notable gene
- crpP in 37 of 59 genomes
A newly published Veterinary Sciences paper adds a deeper layer to a familiar clinical problem: chronic canine otitis externa caused by Pseudomonas aeruginosa. Using archived Hungarian isolates collected in 2010 and 2017, the researchers combined broth microdilution susceptibility testing with long-read whole-genome sequencing to map both the phenotypic resistance profile and the genomic context behind it. The result is a more detailed picture of how this pathogen persists in difficult ear cases, and why treatment can remain frustrating even when standard susceptibility data are available. (mdpi.com)
That matters because P. aeruginosa has long been one of the most troublesome pathogens in canine otitis. Reviews of the field describe it as strongly associated with chronic, suppurative, and recurrent disease, with biofilm formation and both intrinsic and acquired resistance contributing to poor response to therapy. In canine otitis specifically, published literature has described biofilm formation in a substantial share of isolates, helping explain why minimum inhibitory concentrations and real-world treatment response don’t always line up neatly. (pmc.ncbi.nlm.nih.gov)
In the new study, the broader isolate set included 110 canine otitis externa-associated P. aeruginosa isolates that underwent MIC testing, while a subset of 59 matched genomes was used for resistance-focused genomic analysis. According to the publisher’s summary, the study identified reduced susceptibility to multiple agents, with particular concern around fluoroquinolones and aminoglycosides. The authors also reported that crpP, a fluoroquinolone-associated determinant, was present in 37 of 59 genomes and located on plasmid-predicted contigs in six isolates, a finding that raises questions about dissemination potential. (mdpi.com)
The genomic context is part of what makes the paper useful. Rather than simply listing resistance genes, the study focused on resistance-associated genomic determinants and their mobile-genetic-element surroundings. That approach fits with a broader shift in veterinary microbiology toward integrating phenotype, resistance genotype, virulence traits, and genomic mobility, especially for pathogens that circulate in referral settings and repeatedly exposed patients. A companion paper from the same Hungarian isolate collection, published earlier in 2026, found a genetically diverse population with a broad virulence backbone, reinforcing the idea that these difficult ear infections are not being driven by a single clone. (mdpi.com)
Direct outside commentary on this specific paper appears limited so far, but the broader industry reaction to this line of work is consistent. Recent reviews and surveillance-focused papers argue that canine otitis isolates of P. aeruginosa should be watched not just for resistance levels, but also for mobile elements, persistence traits, and overlap with lineages recognized in human healthcare settings. A 2025 genomic study of canine otitis isolates from multiple countries similarly reported high-risk sequence types matching human nosocomial lineages, suggesting that companion-animal isolates deserve closer surveillance than they’ve often received. (pmc.ncbi.nlm.nih.gov)
Why it matters: For veterinary professionals, this study is less about changing first-line treatment tomorrow and more about sharpening the framework for stubborn cases. When a dog presents with recurrent or nonresponsive otitis, especially after repeated antimicrobial exposure, the findings support moving beyond empiric assumptions. Culture, susceptibility testing, and case-specific topical planning remain central, but this paper is a reminder that resistance may be layered, mobile, and only partly captured by a single test result. It also underscores the stewardship challenge: repeated use of fluoroquinolones or aminoglycosides in chronic ears may be selecting within a pathogen population already well equipped to persist. (mdpi.com)
There’s also a One Health angle. Companion animals live in close contact with people, and P. aeruginosa is already a major concern in human healthcare. The presence of mobile genetic elements and plasmid-associated resistance determinants in canine otitis isolates doesn’t prove transmission, but it does support the inference that veterinary surveillance should pay closer attention to how these strains evolve and move through clinics, households, and the environment. That’s especially relevant for specialty and referral practices seeing repeat otitis cases over long time horizons. (mdpi.com)
What to watch: The next important development will be studies that connect these genomic findings to case history, prior drug exposure, and clinical outcome, because that’s what would make the data most actionable for frontline veterinarians. If researchers can show which resistance patterns, mobile elements, or virulence profiles predict treatment failure, culture turnaround decisions and antimicrobial choices in chronic otitis could become much more precise. (mdpi.com)