Antibacterial effects of chitosan-based hydrogels containing Trachyspermum ammi essential oil on pathogens isolated from dogs with otitis externa.

BACKGROUND: Growing antibiotic resistance has made treating otitis externa (OE) increasingly challenging. On the other hand, local antimicrobial treatments, especially those that combine essential oils (EOs) with nanoparticles, tend to be preferred over systemic ones. It was investigated whether Ajwain (Trachyspermum ammi) EO, combined with chitosan nanoparticles modified by cholesterol, could inhibit the growth of bacterial pathogens isolated from OE cases in dogs. In total, 57 dogs with clinical signs of OE were examined and bacteriologically tested. Hydrogels of Chitosan were synthesized by self-assembly and investigated. EO was extracted (Clevenger machine), and its ingredients were checked (GC-MS analysis) and encapsulated in chitosan-cholesterol nanoparticles. Disc-diffusion and broth Micro-dilution (MIC and MBC) examined its antimicrobial and therapeutic properties. RESULTS: Staphylococcus pseudintermedius (49.3%) was the most common bacteria isolated from OE cases, followed by Pseudomonas aeruginosa (14.7%), Escherichia coli (13.3%), Streptococcus canis (9.3%), Corynebacterium auriscanis (6.7%), Klebsiella pneumoniae (2.7%), Proteus mirabilis (2.7%), and Bacillus cereus (1.3%). The investigation into the antimicrobial properties of Ajwain EO encapsulated in chitosan nanoparticles revealed that it exhibited a more pronounced antimicrobial effect against the pathogens responsible for OE. CONCLUSIONS: Using chitosan nanoparticles encapsulated with EO presents an effective treatment approach for dogs with OE that conventional antimicrobial treatments have not cured. This approach not only enhances antibacterial effects but also reduces the required dosage of antimicrobials, potentially preventing the emergence of antimicrobial resistance.

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.

Detection and characterization of potential virulence determinants in Staphylococcus pseudintermedius and S. schleiferi strains isolated from canine otitis externa in Korea.

BACKGROUND: A recent increase in the occurrence of canine skin and soft tissue infections, including otitis externa and pyoderma, caused by antimicrobial-resistant Staphylococcus pseudintermedius and S. schleiferi has become a significant public and veterinary health issues. OBJECTIVE: We investigated the virulence potentials associated with the occurrence of canine otitis externa in S. pseudintermedius and S. schleiferi. METHODS: In this study, the prevalence of genes encoding leukocidins, exfoliative toxins, and staphylococcal enterotoxins (SEs) was investigated using previously characterized S. pseudintermedius (n = 26) and S. schleiferi (n = 19) isolates derived from canine otitis externa. Susceptibility to cathelicidins (K9CATH and PMAP-36) and hydrogen peroxide (H2O2) was also examined in both staphylococcal species. RESULTS: A high prevalence of genes encoding leukocidins (lukS/F-I, lukS1/F1-S, and lukS2/F2-S), exfoliative toxins (siet, expB, and sset), and SEs was identified in both S. pseudintermedius and S. schleiferi isolates. Notably, S. pseudintermedius isolates possessed higher number of SE genes, especially newer SE genes, than S. schleiferi isolates harboring egc clusters. Although no significant differences in susceptibility to K9CATH and H2O2 were observed between the two isolate groups, S. pseudintermedius isolates exhibited enhanced resistance to PMAP-36 compared to S. schleiferi isolates. CONCLUSIONS: These findings suggest that high a prevalence of various toxin genes together with enhanced resistance to cathelicidins may contribute to the pathogenicity of S. pseudintermedius and S. schleiferi in canine cutaneous infections.

Identification of bacteria associated with canine otitis externa based on 16S rDNA high-throughput sequencing.

Bacteria are regarded as predisposing and perpetuating factors causing otitis externa (OE), whereas auricular anatomy is a predisposing factor. This study aims to investigate bacterial populations in the external auditory canals of healthy dogs and dogs with OE. Four categories of ear swabs included healthy erect-ear dogs, erect-ear dogs with OE, healthy pendulous-ear dogs and pendulous-ear dogs with OE. After bacterial DNA extraction, 16S rDNAs were amplified using specific primers within a V3/V4 region. Following DNA library construction, high-throughput sequencing was performed on MiSeq (Illumina). CLC Microbial Genomics Module was used to determine the rarefaction curve, bacterial classification, relative abundance, richness and diversity index. The results demonstrated that healthy dogs had higher bacterial richness and diversity than the dogs with OE. Comparable with culture-dependent methods described previously, this study revealed predominant Corynebacterium spp., Pseudomonas spp., Staphylococcus spp., and Proteus spp. in OE cases. Furthermore, high-throughput sequencing might disclose some potential emerging pathogens including Tissierella spp., Acinetobacter spp., and Achromobacter spp., which have not been reported in previous canine OE cases. Nevertheless, larger sample sizes are further required for an extensive evidence-based investigation.

Short- and long-term outcomes of subtotal ear canal ablation and lateral bulla osteotomy in French bulldogs.

The objective of this retrospective study was to report the overall peri-operative complications and short- to long-term outcomes of subtotal ear canal ablation and lateral bulla osteotomy in French bulldogs with otitis media. Medical records from 2018 to 2021 were reviewed for preoperative neurological signs, surgical technique, postoperative complications, and long-term outcomes. Postoperative complications, such as a head tilt, nystagmus, ataxia, facial nerve dysfunction, as well as skin or wound infection, were recorded. Eighteen client-owned dogs (20 ears) were included in the study. Postoperative complications were observed in 5/18 dogs (6/20 ears) with 2 of them being considered major complications. Referring veterinarians and owner telephone follow-up (mean: 33 mo, range: 17 to 56 mo) were obtained for all patients. Total recovery was reported in 9/18 dogs (11/20 ears) with a postoperative improvement of the vestibular signs and facial nerve paresis within 8 wk. All dogs maintained the pinnas' natural, erect morphology, and movement.

L'objectif de cette étude rétrospective était de rapporter les complications peropératoires globales et les résultats à court et à long terme de l'ablation subtotale du conduit auditif et de l'ostéotomie de la bulle latérale chez les bouledogues français atteints d'otite moyenne. Les dossiers médicaux de 2018 à 2021 ont été examinés pour les signes neurologiques préopératoires, la technique chirurgicale, les complications postopératoires et les résultats à long terme. Les complications postopératoires, telles qu'une inclinaison de la tête, un nystagmus, une ataxie, un dysfonctionnement du nerf facial, ainsi qu'une infection de la peau ou des plaies, ont été enregistrées. Dix-huit chiens de propriétaires (20 oreilles) ont été inclus dans l'étude. Des complications postopératoires ont été observées chez 5/18 chiens (6/20 oreilles) dont 2 ont été considérées comme des complications majeures. Les vétérinaires référents et le suivi téléphonique des propriétaires (moyenne : 33 mois, intervalle : 17 à 56 mois) ont été obtenus pour tous les patients. Une récupération totale a été rapportée chez 9/18 chiens (11/20 oreilles) avec une amélioration postopératoire des signes vestibulaires et une parésie du nerf facial en 8 semaines. Tous les chiens ont conservé la morphologie et le mouvement naturels et dressés des pinnas.(Traduit par Docteur Serge Messier).

Prevalence of the microbiological causes of canine otitis externa and the antibiotic susceptibility of the isolated bacterial strains.

Otitis externa is a canine disease of multifactorial etiology in which bacteria plays a significant role. Due to the predominant bacterial etiology otitis is usually treated with antibiotics. However, non-prudent use of antibiotics promotes the emergence of antibiotic-resistant bacteria thus compromising the therapy effectiveness. Currently, the increase of antimicrobial resistance (AMR) is one of the biggest threats to global health. For this reason, the aim of the study was to investigate prevalence of the microbiological causes of canine otitis externa and the antibiotic susceptibility of the isolated bacterial strains. The research and sampling were conducted at Veterinary Clinics for small pets in Serbia. Samples were sent to laboratory for bacteriological and mycological testing. Additionally, the sensitivity of the isolated bacteria to antibiotics was evaluated using disc diffusion method. Sixty dogs with otitis externa clinical symptoms were included in the study. Out of a total of 53 positive samples for pathogen presence, bacteria were present in 40. The most prevalent bacteria was Staphylococcus pseudintermedius, followed by Pseudomonas aeruginosa and Proteus spp., while Malassezia pachydermatis was the only isolated yeast pathogen occurring in 36 samples. Generally, the lowest resistance against all bacteria showed enrofloxacin. On the contrary, high resistance to penicillin and amoxicillin was a common finding for G+ and G- bacteria. These results indicate the need for laboratory testing in terms of isolation, identification and antibiotic susceptibility testing, not only in the case of otitis externa in dogs, but in all diseases when it is possible, in order to enhance antimicrobial stewardship and consequently to contribute AMR reduction.

A Pandora's box in feline medicine: presenting signs and surgical outcomes in 58 previously hoarded cats with chronic otitis media-interna.

OBJECTIVES: The aim of the present study was to report clinical findings, surgical complications and outcomes for previously hoarded cats treated surgically for otitis media-interna (OMI) and to investigate the risk factors for complications and poor outcomes. METHODS: A retrospective study was conducted of 58 cats from an institutional hoarding environment that underwent ventral bulla osteotomy (VBO). RESULTS: Inappetence was uncommon at presentation (9/58, 16%) compared with pruritus/alopecia (50%), nasopharyngeal signs (45%), otitis externa (OE) (79%) and otitis interna (OI) (ataxia ± head tilt/head excursions) in 40%. Purulent aural discharge occurred in 36% and polyps in 26%. The tympanic bulla wall was moderately or severely thickened radiographically in 38/108 (35%) ears. Cultures were positive for Streptococcus equi subspecies zooepidemicus in 26/48 (54%) cats. Of the 58 cats, 40 (69%) had complications after the first VBO and 19/30 (63%) after the second. Of 101 complications, 56 (55%), from 27/88 (31%) surgeries, were considered serious, including life-threatening perioperative complications in seven, OI in eight, prolonged anorexia in six and worsening of pruritus/alopecia in nine cases. Three cats developed xerostomia (dry mouth) after the second VBO. Pruritus/alopecia, nasopharyngeal signs, OE and purulent aural discharge resolved in a statistically significant proportion of cats but persisted in some. Full resolution of OI was uncommon. OI preoperatively, and surgery performed by a generalist (vs specialist) surgeon, were risk factors for OE at recheck (OI: odds ratio [OR] 4.35; 95% confidence interval [CI] 1.21-15.70; P = 0.02; surgery: OR 3.64; 95% CI 1.03-12.87; P = 0.045). No other prognostic indicators were identified. No variables tested were significantly associated with risk of serious complications or euthanasia. CONCLUSIONS AND RELEVANCE: Surgical management of chronic OMI was successful in most cases but was not benign and not always beneficial. The analysis was unable to identify clinically helpful outcome predictors. Optimal management of chronic feline OMI remains a challenge, particularly for animal shelters. Less invasive approaches and chronic medical management require further investigation.

Refractory otitis media and otitis externa in a koala (Phascolarctos cinereus) treated with total ear canal ablation and lateral bulla osteotomy.

BACKGROUND: To the authors' knowledge, this is the first report fully describing the surgical and medical management of otitis media and otitis externa in the koala (Phascolarctos cinereus) treated by total ear canal ablation and lateral bulla osteotomy. CASE REPORT: An adult male koala captured as part of a monitoring project in South East Queensland was diagnosed with chlamydial cystitis. Purulent discharge from the right ear was also observed; diagnostic imaging was consistent with otitis media and otitis externa. Yokenella regensburgei was repeatedly cultured from the site. Clinical signs resolved with topical antibiotic therapy; however, recrudesced following cessation of antibiotics. A total ear canal ablation and lateral bulla osteotomy was performed, followed by an extended period of systemic antibiotic therapy. Mild facial nerve paresis was observed for 4 weeks postoperatively and resolved spontaneously. The koala remained clinically healthy for the 6 months it was monitored following release. CONCLUSION: Total ear canal ablation combined with lateral bulla osteotomy appears to be an appropriate surgical intervention for otitis media combined with otitis externa refractory to medical management in the koala. Transient postoperative facial nerve paresis is a possible complication, as documented in other species. To the authors' knowledge this is the first case of Yokenella regensburgei infection outside of humans and American alligators (Alligator mississippiensis); the clinical significance of this pathogen in the koala remains unknown.

New variant strain of Streptococcus canis with Lancefield group C isolated from canine otitis externa.

Every basic course in microbiology teaches us, Streptococcus canis always tests positive for Lancefield group G. Surprisingly, we identified a strain of S. canis with Lancefield group C, cultured from a dog with otitis externa after lateral ear canal resection. Whole genome sequencing data and analysis points towards a horizontal gene transfer event between S. canis and S. dysgalactiae. Although these species are closely related, gene transfer in this region of the genome of S. canis has not been described before. The value of technologies as MALDI-TOF MS and sequencing in microbiological diagnostics will grow as more diverse streptococci arise that do not always conform anymore to the classical Lancefield group typing.

Lateral ear canal resection and bulla osteotomy with marsupialization to treat otitis media in rabbits: forty-eight procedures.

OBJECTIVE: Describe lateral ear canal resection and bulla osteotomy with marsupialization (LECARBOM) in rabbits with otitis media (OM), and report outcomes, complications, bacteria cultured from middle ears, and their antimicrobial susceptibility testing (AST) results. STUDY DESIGN: Retrospective clinical case series; single referral hospital. ANIMALS: Forty-two rabbits with naturally occurring OM. METHODS: Medical records (2011-2021) of rabbits with CT-confirmed OM undergoing surgery were reviewed for outcomes, complications, bacteria cultured from middle ears, and AST. RESULTS: Surgery was performed on 48 ears, and outcomes determined 21 days postoperatively. All rabbits survived the procedure. Otitis externa resolved in all lop-eared rabbits. Of 29 ears with OM-associated head tilt, eight (28%) resolved, nine (31%) improved, seven (24%) remained unchanged and five (17%) worsened. Outcome was not associated with head tilt duration nor OM severity. Postoperative complications occurred in 12 (25%) cases, seven of which had wound margin dehiscence that healed by 21 days. The most frequent bacteria isolated were Pasteurella multocida (16%), Bordetella bronchiseptica (14%) and Staphylococcus aureus (14%). Bacteria were sensitive to azithromycin, marbofloxacin or enrofloxacin and resistant to penicillin. CONCLUSION: LECARBOM is a well-tolerated surgical procedure to treat OM. It also improved or stabilized 83% of cases with head tilt and resolved all cases with otitis externa. CLINICAL SIGNIFICANCE: LECARBOM with administration of an AST-sensitive antibiotic, or azithromycin when no AST is performed, should be effective in rabbits with OM. Postsurgically, it resolves or alleviates most secondary conditions such as otitis externa, head tilt and facial nerve paralysis.

Comparison between clinical evaluations and laboratory findings and the impact of biofilm on antimicrobial susceptibility in vitro in canine otitis externa.

BACKGROUND: In canine otitis externa (OE), biofilm-producing bacteria are frequently present but biofilm may be underdiagnosed clinically. HYPOTHESIS/OBJECTIVES: The study aimed to investigate an association between clinical and cytological findings with bacteriological data from dogs with OE, to establish, through Environmental Scanning Electron Microscope (ESEM) examination, whether the presence of biofilm in vivo can be predicted and to evaluate the impact of biofilm on antimicrobial susceptibility tests. MATERIALS AND METHODS: Fifty-six dogs showing clinical signs of OE were enrolled. One cotton swab each was collected for ESEM, bacterial culture and susceptibility testing and for cytology. Staphylococcus pseudintermedius (n = 42, 48.8%) and Pseudomonas aeruginosa (n = 26, 30.2%) were tested for their ability to form biofilm. Minimum Inhibitory Concentrations (MIC), Minimal Biofilm Inhibitory Concentrations (MBIC) and Minimal Biofilm Eradication Concentrations (MBEC) towards enrofloxacin, gentamicin, polymyxin B and rifampicin were determined. RESULTS: Pseudomonas aeruginosa was positively associated with the biofilm clinical evaluation (p < 0.01) and neutrophils (p < 0.05), nuclear streaks (p < 0.01) and rods bacteria (p < 0.01) on cytology. S. pseudintermedius was associated with a low presence of neutrophils. There was a statistical correlation between clinical and cytological biofilm presence (p ≤ 0.01), but none with the biofilm production assay nor ESEM biofilm detection. No differences were found comparing the results of MIC and MBIC. MBEC results showed higher values than MIC and MBIC for all antimicrobials tested (p ≤ 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Biofilm presence in OE was often underdiagnosed. Even if there is no specific clinical or cytological pattern related to biofilm, its presence should always be suspected.

Evaluation of in vitro activity of herbal formula Di Er You and herb Coptis against bacteria isolated from dogs with otitis externa.

OBJECTIVE: To determine the in vitro activity of the herbal formula Di Er You (DEY) and the single-herb Coptis against bacteria cultured from dogs with otitis externa. ANIMALS: 32 client-owned dogs diagnosed with otitis externa. METHODS: A sample of otic debris from each patient was collected and plated onto a fresh Sheep's Blood Agar plate in the hospital. After bacterial growth was confirmed, 4 wells were created, numbered randomly, and treated with saline (placebo), DEY, Coptis, and Zymox Otic Enzymatic Solution with 1% Hydrocortisone (Zymox). After 24 hours of incubation, the diameter of the zone of inhibition (dZOI) of each treatment was measured and recorded, and compared among treatments. A sample of the bacterial colonies grown was submitted to an outside lab for bacterial identification. RESULTS: The mean ± SD dZOI values for saline, DEY, Coptis, and Zymox treated wells were 0.25 ± 1.41, 12.47 ± 3.92, 14.25 ± 7.12, and 3.22 ± 5.12, respectively. Post hoc multiple comparisons test revealed that (1) saline-treated wells had significantly smaller dZOI values than the other 3 groups (all P < .001), (2) Zymox treated wells had significantly smaller dZOI values than either herbal treated groups (both P < .001), and (3) DEY treated wells had significantly smaller dZOI values than those treated with Coptis (P = .0042). CLINICAL RELEVANCE: The results from this in vitro study suggested that both DEY and Coptis could be effective treatments in inhibiting the growth of bacteria in dogs with otitis externa. Prospective randomized controlled clinical trials are warranted to confirm these findings.

Managing recurrent otitis externa in dogs: what have we learned and what can we do better?

Recurrent otitis externa is a common problem in dogs. Topical treatment for each flare is successful in the short term, but repeated cycles of inflammation and infection lead to chronic inflammatory changes, pain and aversion, and antimicrobial resistance. These make the flares more frequent and harder to control. Eventually, the changes become irreversible and require a total ear canal ablation/lateral bulla osteotomy or ablative laser surgery. Most ear canal surgery is avoidable if recurrent otitis is properly managed at an earlier stage. This requires a different mindset and approach to these cases, taking advantage of recent research and clinical findings. Most importantly, clinicians must appreciate that all recurrent ear infections in dogs are secondary. To achieve a good long-term outcome, it is essential that all the underlying factors in each case are diagnosed and managed using the primary, secondary, predisposing, and perpetuating framework. This means that the primary condition must be diagnosed and managed, the secondary infection treated, predisposing risks identified and corrected, and the perpetuating factors reversed. Treatment is in 2 phases: induction to get the ears in remission and then long-term maintenance therapy to prevent relapses. Treatment should be appropriate to each dog but will typically involve ear cleaning, topical antimicrobial therapy, and topical or systemic glucocorticoids. Novel treatments for infection and inflammation will offer additional options in the future. Understanding the triggers for recurrent otitis in dogs will help clinicians plan effective management regimens that will make a huge difference to the quality of life of their patients and their owners.

Comparison of the quantity and antimicrobial activity of host defence peptides in ear canals between healthy and atopic dogs: A preliminary study.

BACKGROUND: Host defence peptides (HDPs) are involved in cutaneous immune defence. The secretion of HDPs in the ears of healthy normal and noninfected atopic dogs has not been measured. HYPOTHESES/OBJECTIVES: The aim of this study was to quantify the concentrations of ß-defensins (cBD3)-like and cathelicidin (cCath) HDPs in ears of healthy and atopic dogs without infectious otitis, additionally to evaluate the antimicrobial effect of the HDPs obtained. ANIMALS: Ten healthy and 20 atopic dogs with mild inflammatory, noninfectious otitis were included. MATERIALS AND METHODS: Absence of infection was determined by cytological evaluation, and the severity of clinical signs, if present, was assessed by a previously validated score (Otitis Externa Scoring System for Clinical Study, OTIS-3). The left ear canal of each dog was rinsed with 2 mL of sodium phosphate buffer. The solution obtained was analysed by enzyme-linked immunosorbent assay to quantify HDPs. Additionally, aural secretions were incubated with two concentrations (5 × 105 and 5 × 104 colony-forming units/mL) of Staphylococcus pseudintermedius and the bacterial density measured after 24 h of incubation. Data were statistically analysed. Significance was set as p ≤ 0.05. RESULTS: There was a significantly lower concentration of HDPs from atopic ears when compared with those from normal healthy dogs (cBD3-like: p = 0.0007; cCath: p = 0.049). There was minimal to variable antimicrobial activity in the aural secretions of both groups. CONCLUSIONS AND CLINICAL RELEVANCE: This study showed, for the first time, that the ear canals of atopic dogs with mild noninfectious otitis contain a lower concentration of cBD3-like and cCath HDPs than those of healthy dogs with normal ears. A consistent antimicrobial activity was not present in the aural secretions from either group.

Perioperative complications and outcomes following partial ear canal ablation and lateral bulla osteotomy in pet rabbits: 20 cases (2009-2021).

OBJECTIVE: To investigate the perioperative complications and outcomes of rabbits undergoing partial ear canal ablation and lateral bulla osteotomy for treatment of chronic otitis. MATERIALS AND METHODS: Surgical logbooks were searched to identify rabbits that underwent partial ear canal ablation and lateral bulla osteotomy between December 2009 and September 2021. Data collected included signalment, history, clinical signs, historical and current medical management, physical examination findings, preoperative diagnostic imaging and aural bacterial culture results, surgical procedure information, duration of hospitalisation, complications and final outcome. RESULTS: Twenty rabbits with chronic, medically unresponsive otitis underwent 27 partial ear canal ablation and lateral bulla osteotomies. Ten rabbits had pre-existing neurologic deficits and 17 had an ear base abscess at the time of surgery. A total of 13 (65%) rabbits developed at least one complication, either in the perioperative period or between discharge and recheck. Three of these rabbits (15%) underwent revision surgery for persistent or recurrent ear base abscess. Complete resolution of clinical signs ultimately occurred in 12 (60%) rabbits. Three (15%) rabbits showed improved but not completely resolved clinical signs (three facial asymmetry). Five (25%) rabbits died of causes potentially related to chronic otitis and/or partial ear canal ablation and lateral bulla osteotomy; two of these rabbits had undergone revision surgery. CLINICAL SIGNIFICANCE: Although this study reports a high complication rate (65%), most complications resolved, with 15 (75%) rabbits having a good to excellent final outcome. Since the majority of rabbits in this study had chronic and severe ear disease, further studies are required to determine if surgical intervention earlier in the disease process could result in a lower complication rate.

Physicochemical properties of otic products for Canine Otitis Externa: comparative analysis of marketed products.

BACKGROUND: Otitis externa is a commonly diagnosed dermatological disorder in canines. The pathogens primarily involved in canine otitis externa (COE) include Staphylococcus pseudintermedius, Pseudomonas aeruginosa, Proteus mirabilis, and Malassezia pachydermatis. As COE tends to be superficial, medications delivered topically are often effective and practical in managing the condition. As such, there is a wide variety of approved topical products currently available in the market. The efficacy of topical dosage forms can be dependent on various factors such as the pharmacology of active constituents and the physicochemical properties of the formulation, including pH, viscosity, spreadability, and bio-adhesion. Currently, there is a lack of published literature available on the optimal properties of topical COE products. In this study, we compared the physicochemical properties of nine commercially available otic veterinarian products in Australia used clinically to manage COE. RESULTS: Based on our comparative analysis, the pH (6.26 ± 0.04) of an aqueous-based product was similar to a healthy dog's external auditory canal. Products containing polymers exhibited higher viscosity and bio-adhesion. Spreadability was inversely related to viscosity and Osurnia ® a product with high viscosity demonstrated the lowest spreadability. Aqueous-based otic products showed better syringebility whereas oil-based systems required higher force to expel the products. Variability in droplet size was noted. Derm Otic, Baytril Otic, and Aurizon Ear Drops had the lower standard deviation which indicates they would give a more consistent dose. CONCLUSIONS: Findings from this work provide considerations for industry researchers or formulation scientists working in the area of otic dosage formulations.

The stability and in vitro antibacterial efficacy of enrofloxacin and gentamicin solutions against Staphylococcus pseudintermedius over 28 days.

BACKGROUND: Many clinicians prepare compounded otic solutions to treat otitis externa (OE). Research evaluating the stability and antimicrobial efficacy of these solutions is limited. HYPOTHESIS/OBJECTIVES: This study determined the chemical stability and in vitro bactericidal efficacy of compounded solutions of enrofloxacin and gentamicin during storage for 28 days. MATERIALS AND METHODS: Solutions of enrofloxacin (10 mg/mL, 1%) and gentamicin (3 mg/mL, 0.3%) were prepared with normal saline and 1 mg/mL dexamethasone. Solutions were stored at room temperature (25°C) for 0, 14 and 28 days. The chemical stability of the antibiotics and dexamethasone were determined using liquid chromatography tandem mass spectrometry in triplicate. Efficacy assessment was made with 10 isolates of Staphylococcus pseudintermedius obtained from dogs with OE. Serial 10-fold dilutions of the bacteria with the compounded solutions were prepared and the colony count results were converted into colony-forming units (cfus). The mean cfu/mL and cfu/mL reduction rates were compared between Day (D)0, D14 and D28. All of the antimicrobial testing solutions were performed in triplicate. RESULTS: Chromatography showed that both antibiotics and dexamethasone were stable for 28 days. No significant differences were observed in the antibiotic bactericidal efficacy of stored solutions at D0, D14 or D28. CONCLUSIONS AND CLINICAL RELEVANCE: Solutions of 1% enrofloxacin and 0.3% gentamicin in normal saline with 0.1% dexamethasone maintained chemical stability and bactericidal efficacy over 28 days. These solutions can be considered as alternatives to commercial preparations for treatment of canine OE when indicated.

Evaluation of hypochlorous acid as an ear flush in dogs with chronic otitis externa.

BACKGROUND: Chronic otitis externa (OE) in dogs frequently requires anaesthetised ear flushing. OBJECTIVES: To evaluate hypochlorous acid as an ear flushing and antimicrobial agent in dogs with chronic OE. ANIMALS: Twenty dogs with chronic OE caused by the same organisms bilaterally. MATERIALS AND METHODS: One ear was flushed under anaesthesia with hypochlorous acid, the other with saline solution. Subsequently, the ear flushed with hypochlorous acid was cleaned with the same solution twice daily for 2 weeks, the other ear with a commercial ear cleaner. An ear medication containing miconazole, polymyxin B and prednisolone was used once daily in both ears. Clinical scores were determined before the flush. Ear cytological results were obtained, a hearing test was conducted before and after the ear flush, and a culture was taken directly after flushing. Ears were evaluated after 2 weeks of therapy. RESULTS: Yeast was present in the ears of 11, cocci in one and a mixed infection in eight dogs. Five ears were negative on culture after flushing with hypochlorous acid, one after the saline flush. Clinical and cytological scores decreased significantly with both solutions after 2 weeks of treatment. There was no difference between treatments in any of the scores at any time point between treatments and in the results of the hearing test before and after the flushing procedure. Adverse effects were not seen. CONCLUSIONS AND CLINICAL RELEVANCE: Hypochlorous acid is a suitable cleaning solution for canine OE.

Long-lasting otic medications may be a rare cause of neurogenic keratoconjunctivitis sicca in dogs.

OBJECTIVE: To characterize the clinical course and long-term prognosis of a suspected novel cause of neurogenic keratoconjunctivitis sicca (nKCS) secondary to florfenicol, terbinafine hydrochloride, mometasone furoate (Claro and Neptra) or florfenicol, terbinafine, betamethasone acetate (Osurnia). ANIMALS: 29 client-owned dogs. PROCEDURES: Online survey and word-of-mouth recruitment were conducted to identify dogs that developed clinical signs of nKCS after application of otitis externa medication containing terbinafine and florfenicol. A retrospective analysis of medical records of dogs meeting inclusion criteria was then conducted. Included dogs had onset of clinical signs of nKCS within 1 day after application of otitis externa medications containing terbinafine and florfenicol and had documentation of low Schirmer tear test value (< 15 mm/min) of affected eyes. RESULTS: 29 dogs with medical records available for review met the inclusion criteria. Documented return of clinically normal tear production was identified in 24 of 29 dogs, with a median time from application of ear medication to documented return of clinically normal tear production of 86 days (range, 19 to 482 days). A corneal ulcer was diagnosed in 68% (20/29). Multivariable Cox regression analysis showed being referred to an ophthalmologist (P = .03) and having a deep ulcer (P = .02) were associated with a longer time to documentation of Schirmer tear test ≥ 15 mm/min. CLINICAL RELEVANCE: Dogs that developed nKCS within 1 day after application of otitis externa medications containing terbinafine and florfenicol had a good prognosis for return of normal tear production within 1 year.

Otitis media and interna with or without polyps in cats: association between meningeal enhancement on postcontrast MRI, cerebrospinal fluid abnormalities, and clinician treatment choice and outcome.

OBJECTIVES: The aim of this study was to evaluate the association between meningeal enhancement (MgE) and cerebrospinal fluid (CSF) analysis results, their individual association with bacteriology results from affected ear samples and whether these test results influenced clinicians' therapeutic choice in cats with otitis media and interna (OMI). METHODS: This was a multicentre retrospective study carried out over an 8-year period. Cats diagnosed with OMI, with or without a nasopharyngeal polyp, leading to peripheral vestibular signs were included. Only cats for which MRI with postcontrast T1-weighted sequences and CSF analyses available were included. Cats with intra-axial MRI lesions or empyema were excluded. RESULTS: Fifty-eight cats met the inclusion criteria. MgE was reported in 26/58 cases, of which nine had an abnormal CSF result (increased total nucleated cell count [TNCC] or total protein); 32/58 cases had no MgE, of which 10 showed abnormal CSF results. There was no association between bacteriology results (external ear canal or bulla) and MgE or abnormal CSF results. CSF abnormalities were statistically significantly more common in acute cases (n = 16/37) than in chronic cases (n = 3/21; Fischer's test P = 0.04). Prednisolone was prescribed in 10/16 cases with increased TNCC. Among the 42 cases with normal TNCC, 15 received prednisolone and 13 received non-steroidal anti-inflammatory drugs. Various antimicrobial drugs were prescribed in 53/58 cats. Duration of antimicrobial treatment was similar, regardless of positive bacterial culture (5.58 vs 4.22 weeks), abnormal CSF (5.83 vs 4.76 weeks) or MgE (5.33 vs 4.90 weeks). CONCLUSIONS AND RELEVANCE: No association was found between the CSF and MgE results. Furthermore, no association was found between MgE, CSF or bacteriology findings. In addition, abnormal CSF results might lead the clinician to treat with corticosteroids, but they did not have any impact on duration of antimicrobial treatment. CSF abnormalities were seen significantly less frequently in chronic cases. The outcome tended to be poorer when MgE was detected on MRI.