Pathogenicity Profiling of Pseudomonas aeruginosa from Canine Otitis Cases from two Veterinary Centers in Kerala, India

Background and Aim: Otitis externa, characterized by inflammation of external ear canal, is a common condition affecting dogs worldwide. The condition is further exacerbated by infections caused by various bacteria, among which Pseudomonas aeruginosa is of critical importance due to its ability to form biofilms and produce different virulence factors resulting in chronic infections. The aim of this study is to isolate Pseudomonas spp. from cases of canine otitis and analyze their pathogenicity profiles.

Study Design: Dogs exhibiting clinical signs of otitis were included in the study. Pathogens were identified using biochemical and molecular methods, and their pathogenicity profiles were assessed biochemically and clustered using K-means clustering.

Methodology: This Cross-sectional study involved 30 specimens from dogs presented at the clinics with signs such as pruritus of the ear, severe pain, head shaking, foul odour, ear discharges and ear scratching suggestive of otitis externa from September 2023-march, 2024 carried out at Wayanad district, Kerala, India. Samples were collected aseptically. Isolation and identification of Pseudomonas spp., were performed using biochemical tests and detection of the OprI gene. Pathogenicity profiles were evaluated based on proteolytic, lipolytic, and hemolytic activities, biofilm production, pyoverdine production, and prevalence of elastase (LasB) gene. Degrees of association between these traits were calculated, and clustering analyses were performed.

Results: Nine isolates (31%) of P. aeruginosa were obtained. Proteolytic and lipolytic activities were present in seven of the nine isolates. Production of elastase and biofilms were observed in only two isolates. Statistical analysis revealed no significant correlation between the traits, except for biofilm formation and elastase production (χ² = 9.009, p = 0.003). Clustering analysis identified an optimal k-value of 4. Two isolates with the most pathogenic traits formed separate clusters, while the one isolate with the fewest traits formed its cluster. All other isolates with varying pathogenicity factors were grouped into one cluster.

Conclusion: The study demonstrated that P. aeruginosa in canine otitis exhibits various pathogenicity factors that contribute to its invasion and nutrient acquisition. These traits appear to function independently. A larger sample size with more traits under consideration may provide better clustering resolution based on pathogenicity profiles.