Pathogens in otitis externa: diagnostic techniques to identify secondary causes of ear disease

Tailoring formulation for enhanced phage therapy in canine otitis externa: a cocktail approach targeting Pseudomonas aeruginosa and Staphylococcus pseudintermedius

Canine otitis externa, characterized by the involvement of diverse bacterial species, notably Pseudomonas aeruginosa and Staphylococcus pseudintermedius, necessitates antibiotic administration as the primary therapeutic approach; however, prolonged treatment often precipitates antibiotic resistance. Therefore, the application of bacteriophages as antimicrobial agents has been of interest recently. However, phage therapy has limitations; its efficacy depends on the lytic capacity of the phage and the emergence of phage resistance, which can be overcome by using phage cocktails. This study aimed to enhance the therapeutic potential of bacteriophages by supplementing additional materials to hinder the pathogens and combining different viruses to broaden the lytic spectrum. The therapeutic potential of the phage cocktail, consisting of Pseudomonas phage pPa_SNUABM_DT01 and Staphylococcus phage pSp_SNUABM-J, was evaluated using an in vitro planktonic bacterial cell lysis assay and a biofilm degradation assay. Additionally, its efficacy was assessed using an in vivo mouse otitis externa model and clinical administration in five dogs with chronic Pseudomonas aeruginosa and Staphylococcus pseudintermedius otitis externa. The phage cocktail with formulation, including glycerol, glycine, and Tween 20, as additional components resulted in a significant reduction in bacterial counts and clinical improvements, including odor, discharge type and amount, and inflammatory symptoms. The results suggest that administering a phage cocktail solution with additional components could make phage therapy a more efficient treatment for otitis externa in dogs. This offers a practical alternative to traditional antibiotic treatments and could help mitigate antibiotic resistance in veterinary medicine.

Clinical safety and efficacy of a single-dose gentamicin, posaconazole and mometasone furoate otic suspension for treatment of canine otitis externa

BACKGROUND

A single-dose, in-clinic, veterinary professional-administered treatment for canine otitis externa was developed to improve compliance and canine welfare.

METHODS

This multicentre, controlled, examiner-masked, randomised field trial was conducted in 316 dogs over 42 days. Dogs were treated once, on day 0, with the investigational product containing gentamicin, posaconazole and mometasone furoate (Mometamax Ultra [MU]) or twice (days 0 and 7) with a control product containing florfenicol, terbinafine and betamethasone acetate (CP). The primary endpoint was a composite otitis index score of 4 or less (of 12) on day 14 and 3 or less (of 12) on day 28.

RESULTS

On day 28, treatment success was recorded in 128 of 143 MU-treated dogs (89.5%), significantly non-inferior to 116 of 133 (87.2%) CP-treated dogs (Farrington-Manning test, Z = 4.1351, p < 0.0001). For mixed cultures of Staphylococcus pseudintermedius and Malassezia pachydermatis, there was 100% treatment success in MU-treated dogs (n = 33), significantly non-inferior to 90.2% (37 of 41) in CP-treated dogs (Farrington-Manning test, Z = 3.1954, p = 0.0007).

LIMITATIONS

Efficacy in chronic otitis externa cases was not investigated. Cytology was not used to aid in diagnosis or for identification of secondary pathogens.

CONCLUSION

This unique combination, single-dose product is safe and effective in dogs with otitis externa. It offers enhanced compliance, canine welfare and quality of life by eliminating the owner burden of treating this painful condition.

Pseudomonas spp. in Canine Otitis Externa

Canine otitis externa (OE) is a commonly diagnosed condition seen in veterinary practice worldwide. In this review, we discuss the mechanisms of the disease, with a particular focus on the biological characteristics of Pseudomonas aeruginosa and the impact that antibiotic resistance has on successful recovery from OE. We also consider potential alternatives to antimicrobial chemotherapy for the treatment of recalcitrant infections. P. aeruginosa is not a typical constituent of the canine ear microbiota, but is frequently isolated from cases of chronic OE, and the nature of this pathogen often makes treatment difficult. Biofilm formation is identified in 40-95% of P. aeruginosa from cases of OE and intrinsic and acquired antibiotic resistance, especially resistance to clinically important antibiotics, highlights the need for alternative treatments. The role of other virulence factors in OE remains relatively unexplored and further work is needed. The studies described in this work highlight several potential alternative treatments, including the use of bacteriophages. This review provides a summary of the aetiology of OE with particular reference to the dysbiosis that leads to colonisation by P. aeruginosa and highlights the need for novel treatments for the future management of P. aeruginosa otitis.

A randomized placebo-controlled trial of the efficacy and safety of a terbinafine, florfenicol and betamethasone topical ear formulation in dogs for the treatment of bacterial and/or fungal otitis externa

BACKGROUND

Treatment of infected otitis externa (OE) relies on the topical application of specific formulations that most often contain an antibiotic, an antifungal and a glucocorticoid. This study is to report the results of a randomized, placebo-controlled field trial evaluating the efficacy and safety of OSURNIA™ (Elanco Animal Health, a division of Eli Lilly and Company, Greenfield, IN), a novel topical ear medication containing florfenicol, terbinafine and betamethasone acetate in an adaptable gel. The study includes 284 dogs with bacterial and/or fungal OE who were randomly assigned to receive two doses of Osurnia or its vehicle, one week apart. Dogs were evaluated at various time points through Day 45, and a total clinical score (TCS) was calculated based on pain, erythema, exudate, swelling, odor and ulceration. The primary outcome measure was the rate of treatment success (RTS), defined as a TCS of 0, 1 or 2 on Day 45. Before and after treatment, a "clap test" was performed to subjectively assess hearing, and blood and urine were collected for routine clinical pathology.

RESULTS

The RTS was significantly higher in ears treated with Osurnia (64.78%) than with placebo (43.42%). There was no significant interaction between efficacy and duration of history, recurrence of otitis or body weight. Adverse events were similar between groups. All dogs treated with Osurnia maintained their hearing, and there were no relevant clinical pathology changes.

CONCLUSIONS

The application of two doses of Osurnia, one week apart, is effective and safe to treat microbial otitis externa in dogs.