Preventive use of a topical anti-inflammatory glucocorticoid in atopic dogs without clinical sign of otitis does not affect ear canal microbiota and mycobiota

Effect of a ceruminolytic ear cleaner on clinical, microbiological and ear canal microbiome evolution in canine erythemato-ceruminous otitis externa associated with proliferation of Malassezia yeasts

BACKGROUND

Erythemato-ceruminous otitis externa (ECOE) is commonly associated with Malassezia spp. and microbial imbalance.

HYPOTHESIS/OBJECTIVE

To assess the clinical performance of an ear cleaner in dogs suffering from ECOE associated with Malassezia spp. overgrowth and to measure its impact on the microbiota.

ANIMALS

Thirty privately owned dogs suffering from mild-to-moderate ECOE associated with Malassezia spp. overgrowth.

MATERIALS AND METHODS

Pruritus score (PS), clinical score (0-3 Otitis Index Score [OTIS3]: based on secretions, erythema, hyperplasia and ulceration) and cytological score (CS) were assessed on Day (D)0, D7, and D14. Sterile ear swabs were used on D0 and D14 to perform fungal culture DNA extraction, and PCR amplification of the 18 ITS and 16S rRNA gene was carried out to evaluate the composition and changes of the otic microbiome. Ears were cleaned with a cerumenolytic ear cleanser daily, every other day, or twice a week depending on the secretion score.

RESULTS

Fifty-seven ears (30 dogs) completed the study. PS, OTIS-3, and CS were significantly decreased at D7 and D14 (-45%, -43%, -60% and -77%, -66%, -76%, respectively; p < 0.0001 Wilcoxon test). Fungal culture was positive (Malassezia spp.) in only 34 ears at D0 and was negative in all ears at D14. Mycobiota composition was significantly different before and after treatment with an increase of fungal diversity (Shannon index; p < 0.003 Wilcoxon test) at D14 compared to D0. There was no change in bacterial composition.

CONCLUSIONS AND CLINICAL RELEVANCE

In case of ECOE associated with Malassezia spp. overgrowth, the use of the tested ear cleaner showed a positive impact on the fungal dysbiosis and Malassezia spp. overgrowth.

The role of the microbiome in allergic dermatitis-related otitis externa: a multi-species comparative review

The external ear canal, characterized by species-specific structural and physiological differences, maintains a hostile environment that prevents microbial overgrowth and foreign body entry, supported by factors such as temperature, pH, humidity, and cerumen with antimicrobial properties. This review combines several studies on the healthy ear canal's structure and physiology with a critical approach to the potential existence of an ear microbiome. We use a comparative multi-species approach to explore how allergic conditions alter the ear canal microenvironment and cerumen in different mammalian species, promoting pathogen colonization. We propose a pathogenetic model in which allergic conditions disrupt the antimicrobial environment of the EEC, creating circumstances favorable for facultative pathogenic micro-organisms like Staphylococcus and Malassezia species, leading to otitis externa (OE). A better understanding of the underpinning mechanisms may lead to innovative approaches to disease mitigation.

Long-lasting otic solution containing mometasone furoate can influence intradermal testing in dogs with healthy ears and otitis externa

BACKGROUND

Topical therapy is preferred for otitis externa (OE) in dogs. Otic products commonly contain glucocorticoids that can be systemically absorbed and possibly interfere with diagnostic tests such as intradermal testing (IDT).

HYPOTHESIS/OBJECTIVES

To determine the effect of a long-lasting otic solution containing mometasone furoate (MF) on IDT immediate reactions and to determine withdrawal time before IDT.

ANIMALS

Seventeen dogs with healthy ears (Group 1) and 12 with OE (Group 2).

MATERIALS AND METHODS

Intradermal injections of histamine, anticanine-immunoglobulin (Ig)E and saline were subjectively and objectively evaluated before treatment and weekly for 6 weeks, after a single application of a long-lasting otic solution containing MF.

RESULTS

Statistically significant reductions in the mean subjective histamine scores after application of MF were observed at Weeks 1 (p = 0.012) and 2 (p = 0.028) in Group 1, and Weeks 1 (p = 0.00066), 2 (p = 0.02) and 4 (p = 0.034) in Group 2. Mean histamine objective scores were significantly reduced in Weeks 1 (p = 0.042), 2 (p = 0.0009), 3 (p = 0.001) and 5 (p = 0.018) in Group 1 only. The mean subjective anticanine-IgE scores were significantly reduced in Week 1 in both groups (p = 0.003, p = 0.0066), respectively. There were no significant changes in the mean anticanine-IgE objective score in either group.

CONCLUSIONS AND CLINICAL RELEVANCE

Application of a long-lasting otic solution containing MF can interfere with IDT immediate reactions in healthy and OE dogs. Based on the subjective evaluation, IDT can be performed ≥2 weeks after application of the otic solution in healthy dogs, and ≥4 weeks in dogs with OE.

Efficacy and safety of a hydrocortisone aceponate-containing ear spray solution in dogs with erythemato-ceruminous otitis externa: A randomised, multicentric, single-blinded, controlled trial

BACKGROUND

Erythemato-ceruminous otitis externa (ECOE) is frequently seen in dogs affected with an allergic skin disease, with recurrent secondary bacteria and yeast overgrowths (detected on cytological examination).

OBJECTIVES

The objective of the study was to compare the efficacy and safety of an ear spray containing only hydrocortisone aceponate glucocorticoid diester (HCA) to a control product (CTRL), an approved otic formulation containing prednisolone-miconazole-polymyxin combination, in dogs with ECOE.

ANIMALS

In total, 97 and 104 dogs with ECOE were respectively randomly assigned to the tested ear treatment product group (HCA) or the commercially available ear treatment control product group (CTRL).

MATERIALS AND METHODS

Dogs were treated for 7-14 days, as needed. At Day (D)0, D7, D14, D28 and D42, Otitis Index Score-3, hearing test, pruritus and pain visual analogue scales, and cytological scores were graded. The overall response to treatment also was assessed.

RESULTS

All clinical parameters decreased rapidly and in a similar way without any significant difference at any time between treatment groups. A good-to-excellent response to treatment was seen in >90% of dogs of both groups as early as D14. The treatment was considered safe in all dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

A 7- to 14-day ear topical application of HCA alone to dogs with ECOE accompanied with bacterial and/or fungal (yeast) overgrowth was safe and led to no statistical difference in improvement of clinical scores relative to the CTRL combination. Based on these results, it may be necessary to reconsider the routine use of antimicrobial drugs such as antibiotics and antifungals as a first-line treatment for ECOE that is likely to have been caused by an allergic reaction.

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.

External Ear Canal Evaluation in Dogs with Chronic Suppurative Otitis Externa: Comparison of Direct Cytology, Bacterial Culture and 16S Amplicon Profiling

A discrepancy between cytology and bacterial culture methods is sometimes observed in canine otitis externa. The objective of this study was to compare results from cytology, bacterial culture and 16S amplicon profiling. Twenty samples from 16 dogs with chronic suppurative otitis externa were collected. A direct cytological evaluation was carried out during the consultations. Aerobic bacterial culture and susceptibility were performed by an external laboratory used in routine practice. For 16S amplicon profiling, DNA was extracted and the hypervariable segment V1−V3 of the 16S rDNA was amplified and then sequenced with a MiSeq Illumina sequence carried out by the Mothur software using the SILVA database. A good correlation between cytology and bacterial culture was observed in 60% of the samples. Some bacterial species revealed by bacterial culture were present with low relative abundance (<10%) in 16S amplicon profiling. Some bacterial species revealed by the 16S amplicon profiling analysis were not identified with culture; most of the time, the offending species was a Corynebacterium. To conclude, a careful interpretation of the results of bacterial culture should be made and always be in agreement with the cytology. The 16S amplicon profiling method appears to be a more sensitive method for detecting strains present in suppurative otitis but does not provide information on bacterial susceptibility.