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.

Fungal Otitis Externa (Otomycosis) Associated with Aspergillus Flavus: A Case Image.

A 48-year-old man presented with a chief complaint of intermittent right ear otorrhea of several-month duration, occasional otalgia and progressive unilateral hearing impairment. He also reported frequent episodes of headache and pressure in the sinuses and maxilla. Previous systemic treatment with antibiotics failed to alleviate the symptoms. A head/neck CT showed completely normal mastoid, middle ear and external auditory canal regions without any evidence of opacification or bone erosion. Otoscopic examination of the right ear disclosed aggregates of dried, brown, fibrillar material and debris occluding the external auditory canal and obstructing the otherwise intact tympanic membrane. Dilation of the external auditory canal or thickening of the tympanic membrane were not appreciated. The canal was debrided and the fibrillar material was placed in formalin. Histopathologic examination revealed numerous branching, septated fungal hyphae organized in densely-packed clusters. In other areas, the fungal hyphae abutted or were attached to lamellated collections of orthokeratin. As highlighted by GMS staining, the fungi were morphologically compatible with Aspergillus species. The clinicopathologic findings supported a diagnosis of fungal otitis externa, while the numerous anucleate squamous cells were compatible with colonization of an underlying, probably developing, cholesteatoma. Culture of material isolated from the external auditory canal confirmed the presence of Aspergillus flavus. In this illustrative case, we present the main clinical and microscopic characteristics of Aspergillus-related otomycosis developing in the setting of a tautochronous cholesteatoma.

Diagnostic accuracy of eosinophil-to-lymphocyte ratio and eosinophil-to-neutrophil ratio as biomarkers for differentiating between fungal and bacterial infection in necrotising otitis externa.

INTRODUCTION: Necrotizing otitis externa (NOE) is a serious, progressive, and potentially life-threatening infection of the external auditory canal, affecting soft tissue and bone. The most common organism causing NOE is Pseudomonas Aeruginosa and less common are Fungal infections. When managing a patient with NOE, a culture is taken from the EAC in order to tailor the appropriate antimicrobial treatment, however commonly, the culture is sterile. Inflammation biomarkers may be used as adjuncts to inform on the differential diagnosis and as prognostic markers. AIM: To characterize and compare values and ratios of components of the complete blood count (CBC) at admission, at patients with positive swab culture. METHODS: A retrospective study of NOE patients was conducted. We included all patients admitted between the years 2001-2023, for whom a culture swab tested positive. We compared CBC findings at hospitalization between bacteria and fungi-positive culture patients. RESULTS: Eosinophils-to-Neutrophils Ratio (ENR) was significantly lower in the fungal group compared to the bacterial group 0.023 ± 0.02 and 0.04 ± 0.03, respectively (p-value = 0.025). Eosinophils-to-Leukocyte Ratio (ELR) was significantly lower in the fungal group compared to the bacterial group 0.058 ± 0.04 and 0.12 ± 0.1 respectively (p-value = 0.009). For definition of ELR ≤ 0.1 we found that, sensitivity was 88% (95%CI = 0.679-0.979) and NPV 90% (95%CI = 0.709-0.982). For definition of ENR ≤ 0.03 sensitivity was 88% (95%CI = 0.679-0.979) and NPV 88% (95%CI = 0.679-0.979). CONCLUSION: Lower values of ELR and ENR in patients with NOE are associated with fungal infection and can serve as a tool in adjusting an appropriate antimicrobial therapy in cases of sterile or when no culture is available.

Predictive role of facial nerve palsy improvement in malignant external otitis.

PURPOSE: To evaluate the effects of different factors on facial nerve palsy improvement in patients with malignant external otitis (MEO) and the predictive role of improvement on MEO. METHODS: Data were collected from all MEO patients with facial paralysis who were hospitalized between 2012 and 2017 at a tertiary referral center. We contacted patients at least 6 months after their admission to evaluate their facial nerve function and survival rate. RESULTS: In a study of 19 samples with a mean age of 69.1 years, 9 patients (47.7%) had some or complete improvement, while 10 (52.6%) had no or very minimal improvement. In this study, there was no statistically significant difference between patients with and without facial nerve palsy improvement in terms of age, sex, usage of antifungal treatment alongside antibiotics, duration of hospital stays, HbA1c level, presentation of hearing loss and vertigo, the severity of facial palsy, comorbidity score, mean of fasting blood sugar, leukocytosis, first ESR and ESR drop, CRP and physiotherapy. We found a positive correlation between improving facial palsy and patients' survival rates. CONCLUSION: Considering the possible influence of facial paralysis improvement prognosis on MEO patients' survival, it could affect our approach to the disease.

Systematic review of the diagnosis and management of necrotising otitis externa: Highlighting the need for high-quality research.

OBJECTIVES: To present a systematic review and critical analysis of clinical studies for necrotising otitis externa (NOE), with the aim of informing best practice for diagnosis and management. DESIGN: Medline, Embase, Cochrane Library and Web of Science were searched from database inception until 30 April 2021 for all clinical articles on NOE. The review was registered on PROSPERO (ID: CRD42020128957) and conducted in accordance with PRISMA guidelines. RESULTS: Seventy articles, including 2274 patients were included in the final synthesis. Seventy-three percent were retrospective case series; the remainder were of low methodological quality. Case definitions varied widely. Median patient age was 69.2 years; 68% were male, 84% had diabetes and 10% had no reported immunosuppressive risk factor. Otalgia was almost universal (96%), with granulation (69%) and oedema (76%) the commonest signs reported. Pseudomonas aeruginosa was isolated in 62%, but a range of bacterial and fungal pathogens were reported and 14% grew no organism. Optimal imaging modality for diagnosis or follow-up was unclear. Median antimicrobial therapy duration was 7.2 weeks, with no definitive evidence for optimal regimens. Twenty-one percent had surgery with widely variable timing, indication, or procedure. One-year disease-specific mortality was 2%; treatment failure and relapse rates were 22% and 7%, respectively. CONCLUSION: There is a lack of robust, high-quality data to support best practice for diagnosis and management for this neglected condition. A minimum set of reporting requirements is proposed for future studies. A consensus case definition is urgently needed to facilitate high-quality research.

A Different Era for Malignant Otitis Externa: The Non-Diabetic and Non-Immunocompromised Patients.

BACKGROUND: Τo investigate the differences in regard to the clinical, laboratory, and imaging findings as well as the treatment course between diabetic and non-diabetic, non-immunocompromised patients with malignant otitis externa. METHODS: A total of 36 hospitalized patients diagnosed with malignant otitis externa between January 2011 and December 2020 were divided into 2 groups according to their medical history, blood glucose, and glycated hemoglobin levels. RESULTS: Thirty-two patients were diabetic (group A) and 4 were non-diabetic, non-immunocompromised (group B). Otalgia was present in all patients (100%), followed by otorrhoea (67%) and edema (64%). Polyps were present in 18 patients (50%). Pseudomonas aeruginosa was isolated in 16 out of 25 positive cultures (64%). Four patients of group A and none of group B underwent surgery. Five patients of group A and none of group B had at least 1 cranial nerve involvement. The mean age was 77.22 ± 8.17 for group A and 47.25 ± 3.59 for group B (P < .001). No statistical significance was observed in regards to major symptoms, inflammatory markers (white blood cell, C-reactive protein, and erythrocyte sedimentation rate), positive imaging, and microbiological findings between the 2 groups. The average days of hospitalization were 42.41 ± 31.06 for group A and 10.25 ± 2.63 for group B (P < .049). Four diabetic patients died. CONCLUSION: Non-diabetic, non-immunocompromised adult patients with malignant otitis externa had a better response to antibiotic therapy and a shorter length of hospitalization. A high clinical suspicion for malignant otitis externa should always raise in cases of otitis externa that fail to respond in a topic and/or oral antibiotic treatment for more than a week.

Malignant otitis externa: An updated review.

Malignant otitis externa is a progressive infection of the external auditory canal and skull base. Pseudomonas aeruginosa is the most isolated microorganism and it affects mostly to diabetic, elderly, and immunocompromised individuals. Non-resolving otalgia and chronic otorrhea are the clinical manifestations presented. Facial nerve palsy is a common and well recognized complication. (Computed tomography) CT scan is useful for initial assessment, Technetium-99m is highly sensitive and is part of the protocol for diagnosis. Treatment should be individualized, with multidisciplinary cooperation among specialties. Management involves systemic antipseudomonal antibiotics and monitoring with radiologic techniques, it also involves the strict control of diabetes. It is essential to follow up the patients for at least a year post-treatment. In refractory malignant otitis externa and affection of facial nerve, surgical management is recommended. We reviewed the most recent studies on epidemiology, clinical manifestations, diagnosis, and treatment to provide an update on Malignant Otitis Externa that can offer an overview for clinical practice and future research.

Candida Skull Base Osteomyelitis: a Case Report and Literature Review.

Skull base osteomyelitis (SBO) also commonly known as malignant otitis externa was first described by Meltzer and Kelemen in 1959. Prior to the advent of the antibiotic era, this disease carried a poor prognosis with significant morbidity. It often proved fatal with mortality rates as high as 50%. Commonly seen in the immunocompromised patients, diabetes mellitus is an important associated comorbidity in the pathophysiologic development of this disease. Treatment is instituted by medical therapy with surgery having a limited role. Surgical intervention has a limited role, for example, in fungal SBO. Such cases may require local debridement and intraoperative tissue biopsies for histopathologic confirmation. This is to demonstrate fungal invasion into the skull base, as well as to exclude other sinister differential diagnoses like squamous cell carcinoma of temporal bone. In this case report, we present a rare case of candida SBO and the literature review.

An emergency medicine-focused review of malignant otitis externa.

INTRODUCTION: Malignant otitis externa (MOE) is a progressive infection of the external auditory canal (EAC). This disease is rare but has severe morbidity and mortality. OBJECTIVE: This narrative review provides an overview of malignant otitis externa for emergency clinicians. DISCUSSION: MOE is an invasive external ear infection that spreads to the temporal bone and can further progress to affect intracranial structures. Complications of advanced MOE include cranial nerve involvement, most commonly the facial nerve, and intracranial infections such as abscess and meningitis. The most common causative agent of MOE is Pseudomonas aeruginosa, but others include methicillin-resistant Staphylococcus aureus and fungi. Major risk factors for MOE include diabetes mellitus, immunosuppression, and advanced age. Red flags for MOE include severe otalgia (pain out of proportion to exam) or severe otorrhea, neurologic deficits (especially facial nerve involvement), previously diagnosed otitis externa not responsive to therapy, and patients with major risk factors for MOE. Examination may show purulent otorrhea or granulation tissue in the EAC, and culture of EAC drainage should be performed. Diagnosis is aided by computed tomography (CT) with intravenous contrast, which may demonstrate bony destruction of the temporal bone or skull base. When suspecting MOE, early consultation with an otolaryngologist is recommended and antibiotics with pseudomonal coverage are needed. Most patients with MOE will require admission to the hospital. CONCLUSIONS: MOE is a rare, yet deadly diagnosis that must be suspected when patients with immunocompromise, diabetes, or advanced age present with severe otalgia. Rapid diagnosis and treatment may prevent complications and improve outcomes.

Aspergillus necrotizing otitis externa with temporomandibulozygomatic involvement.

INTRODUCTION: Aspergillus necrotizing otitis externa (NOE) is a rare disease, often associated with delayed diagnosis, the management of which is poorly defined. SUMMARY: The authors report a case of Aspergillus flavus necrotizing otitis externa with temporomandibular arthritis and temporozygomatic osteomyelitis with Staphylococcal coinfection in a diabetic patient. The diagnosis and discontinuation of treatment were guided by PET-CT scan. A favourable course without sequelae was observed after repeated surgical curettage and 3 months of antifungal therapy. DISCUSSION: Aspergillus flavus is the agent most commonly incriminated in NOE. Indirect diagnostic tests (serology) may be negative. The diagnosis is based on imaging-guided surgical biopsy with histological examination and standard and fungal microbiological culture. Treatment requires a combination of surgery and antifungal therapy. The duration of antifungal therapy is poorly defined and discontinuation of therapy can be guided by PET-CT scan.

Malignant Otitis Externa: Causes for Various Treatment Responses.

OBJECTIVES: Malignant (necrotizing) otitis externa (MOE) is an aggressive form of skin inflammation of the external ear with a tendency to spread infection to the temporal bone. The study aimed to evaluate a causal relationship between treatment responses and clinical features in patients with MOE. MATERIALS AND METHODS: In a retrospective, descriptive section study, the database was analyzed between January 2008 and December 2018 in our department, all patients with diagnosed MOE were identified. RESULTS: A total of 30 patients were evaluated, of which 27 men and 3 women. The youngest patient was 52 years old while he was eldest 88 years, (mean-71 years old). As the most common comorbidity, diabetes mellitus was found in 23 (76%) subjects. Median duration of symptoms was about 3 months. The most common isolated pathogen was Pseudomonas aeruginosa (47%). Patients with facial nerve palsy and erosion of temporal bone find on computerized tomography affect prolonged stationary treatment (Mean, SD 29.2±8.5 and 26,7±11.6 days), while 80% of patients with facial nerve palsy had recurrence of disease (p=0.005) with mean duration of clinical remission of 60±17.3 days. Overall length of treatment is also increased in the presence of comorbidities as well as in patients with cranial nerve involvement. CONCLUSION: Patients with cranial nerve involvement, erosion of temporal bone and presence of comorbidities affect prolonged treatment and adverse prognosis. Early diagnosis and initiation of aggressive therapy are essential for stopping the further spread of the disease and prevention of serious complications.

Aspergillus flavus malignant external otitis in a diabetic patient: case report and literature review.

PURPOSE: Malignant external otitis is an aggressive and potentially life-threatening infection. This rare disorder is typically caused by Pseudomonas aeruginosa and affects almost exclusively elderly diabetic patients. However, fungal malignant external otitis have been identified, especially in immunocompromised hosts. METHODS: We report a rare case of invasive malignant external otitis caused by Aspergillus flavus in a diabetic patient without other underlying immunosuppression. A review of Aspergillus spp. malignant external otitis since voriconazole became the first line for invasive aspergillosis was performed. RESULTS: A 72-year-old man with diabetes mellitus developed invasive malignant external otitis with a vascular involvement. The patient was treated with empiric courses of antibiotics until a fungal infection was diagnosed. Proven Apsergillus infection was based on histopathological examination and isolation of A. flavus from culture of osteo-meningeal biopsies. Despite optimal antimicrobial therapy with voriconazole, the patient presented with cerebral infarction in the setting of an angioinvasive fungal infection leading to a fatal outcome. From a review of the literature, we found 39 previously published cases of proven Aspergillus spp. malignant external otitis treated with new triazoles. CONCLUSION: Given our experience and the literature review, a fungal etiology should be considered early in the course of malignant external otitis unresponsive to a conventional broad spectrum antibiotic therapy, with the need for a tissue biopsy to confirm the diagnosis.

Patulous Eustachian tube and palatine defect in a Dachshund with chronic unilateral otitis externa and otitis media.

BACKGROUND: Patulous Eustachian tube (pET) is a rare dysfunction of the Eustachian tube described in humans. It is characterized by failure of the ET to close, resulting in unrestricted passage of air, sound and material between the nasopharynx and the middle ear. OBJECTIVE: To report a case of pET associated with otitis in a dog. ANIMAL: A 6-year old-female spayed Dachshund dog. METHODS AND MATERIALS: Otoscopic examination, cytological evaluation, culture and susceptibility, computerized tomography (CT), video-otoscopic flushing and surgery. RESULTS: Left ear otoscopic examination revealed erythema, purulent frothy discharge, ceruminous gland hyperplasia, stenosis and a partial tear of the tympanum. Cytological evaluation from the left external canal showed neutrophils, macrophages, rods and cocci. Aerobic culture showed predominantly multidrug-resistant Pseudomonas aeruginosa. The CT findings of the left ear included chronic changes in the external canal, marked lysis of the tympanic bulla and marked dilation of the ET. During video-otoscope flushing, saline drained through the mouth. Bilateral incomplete hypoplasia of the soft palate was noted. Total ear canal ablation and bulla osteotomy with ET dissection were curative. Histopathological findings were compatible with chronic otitis externa (OE) and media. CONCLUSION AND CLINICAL IMPORTANCE: To the best of the authors' knowledge, this is the first case of pET described in animals. The ET dysfunction and palatine defect were likely the cause of the otitis in this dog. Clinicians should investigate pET in animals with signs of OE characterized by frothy liquid and food fragments in the ear canal in addition to sneezing after drinking water.

In vitro antibacterial activity of the manuka essential oil from Leptospermum scoparium combined with Tris-EDTA against Gram-negative bacterial isolates from dogs with otitis externa.

BACKGROUND: The increasing prevalence of antimicrobial resistance among bacteria in dogs with otitis externa has led to a need for novel therapeutic agents. HYPOTHESIS/OBJECTIVE: To examine the antibacterial effects of manuka oil combined with ethylenediaminetetraacetic acid-tromethamine (Tris-EDTA) against Gram-negative bacteria isolates from dogs with otitis externa. METHODS AND MATERIALS: A total of 53 clinical isolates including Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae ssp. pneumoniae and Proteus mirabilis. Antimicrobial susceptibility was determined using disk diffusion; the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of manuka essential oil, with or without Tris-EDTA, were investigated. RESULTS: A total of 44 isolates were resistant to at least one antibiotic and 19 strains were multidrug-resistant, with resistance to at least one agent in three or more antimicrobial classes. The MICs and MBCs of manuka oil alone were ≥1% (v/v) and ≥2% (v/v), respectively. There was no antimicrobial effect of Tris-EDTA (1.125:0.3 mg/mL) without manuka oil. However, the combination of manuka oil with Tris-EDTA significantly decreased the MICs (ranging from 0.06% to 0.5%, v/v; P < 0.001) and MBCs (ranging from 0.06% to 1%, v/v; P < 0.001). There also was no significant difference between multidrug-resistant and nonresistant bacterial isolates in terms of the antimicrobial activity of manuka oil with Tris-EDTA. CONCLUSIONS AND CLINICAL IMPORTANCE: The study findings suggest that manuka oil, especially when combined with Tris-EDTA, may be a promising alternative therapeutic option for Gram-negative otic pathogens. Clinical studies are needed to assess potential for in vivo ototoxic effects and efficacy.

Antibacterial effect of N-acetylcysteine in combination with antimicrobials on common canine otitis externa bacterial isolates.

BACKGROUND: Approved treatments for canine otitis externa are limited in variety and may contain ototoxic ingredients. With bacterial resistance an ongoing concern, it would be ideal if non-ototoxic agents combined with antibiotics resulted in a synergistic effect, requiring lower antibiotic concentrations to treat infections. Evidence of synergism and antagonism between N-acetylcysteine (NAC) and various antibiotic classes has been reported; the present research group was interested in examining these interactions. HYPOTHESIS/OBJECTIVES: To determine if NAC, an otoprotective and antimicrobial compound, has synergistic activity when combined with enrofloxacin or gentamicin in vitro against bacterial isolates causing canine otitis externa. ANIMALS: Twenty-two isolates from canine clinical cases of otitis externa were identified and tested, including seven Staphylococcus pseudintermedius, 12 Pseudomonas aeruginosa and three Corynebacterium spp. isolates. METHODS AND MATERIALS: Each isolate was grown on blood agar for 24 h and transferred to Mueller-Hinton broth (MHB), with a final concentration of 5 × 105 cfu/mL. Each well was inoculated with 50 µL of bacterial suspension. N-acetylcysteine was diluted in MHB to a starting concentration of 160 mg/mL. Enrofloxacin and gentamicin were diluted to 64 µg/mL. Individual and checkerboard serial microdilution assays were performed in triplicate with negative controls for all isolates tested. RESULTS: Interactions observed for NAC and enrofloxacin were synergistic (4.5%), indifferent (77.3%) or antagonistic (18.2%). Interactions observed for NAC and gentamicin were synergistic (4.5%), indifferent (45.5%) or antagonistic (50%). CONCLUSIONS AND CLINICAL RELEVANCE: Most interactions between NAC and enrofloxacin or gentamicin were indifferent or antagonistic at the concentrations tested in vitro.

Antimicrobial activity of thyme oil, oregano oil, thymol and carvacrol against sensitive and resistant microbial isolates from dogs with otitis externa.

BACKGROUND: Multidrug-resistant pathogens present a major global challenge in antimicrobial therapy and frequently complicate otitis externa in dogs. HYPOTHESIS/OBJECTIVES: In vitro efficacy of oregano oil, thyme oil and their main phenolic constituents against bacterial and fungal isolates associated with canine otitis externa were investigated. It was hypothesized that the main phenolic components would have greater antimicrobial activity compared to the relative essential oil. METHODS AND MATERIALS: Antimicrobial susceptibility testing was performed using broth microdilution with spot-plating technique to determine minimum inhibitory and bactericidal/fungicidal concentrations (MICs, MBCs and MFCs). A time-kill kinetics assay was performed to confirm the bactericidal and fungicidal activity of the oils and their phenolic constituents. One hundred bacterial and fungal isolates, including meticillin-susceptible Staphylococcus pseudintermedius (n = 10), meticillin-resistant S. pseudintermedius (n = 10), ß-haemolytic Streptococcus spp. (n = 20), Pseudomonas aeruginosa (n = 20; including 10 isolates resistant to one or two antimicrobials), Proteus mirabilis (n = 20) and Malassezia pachydermatis (n = 20) from dogs with otitis externa were used. RESULTS: Oregano oil, thyme oil, carvacrol and thymol exhibited antibacterial activity against all bacterial and fungal isolates tested. MIC90 values ranged from 0.015 to 0.03% (146-292 µg/mL) for the Gram-positive bacteria and P. mirabilis. For P. aeruginosa and M. pachydermatis, MIC90 values ranged from 0.09 to 0.25% (800-2,292 µg/mL). CONCLUSIONS AND CLINICAL SIGNIFICANCE: Oregano oil, thyme oil, carvacrol and thymol showed good in vitro bactericidal and fungicidal activity against 100 isolates from dogs with otitis externa, including some highly drug-resistant isolates. These essential oils and their main phenolic constituents have the potential to be further investigated in vivo for the treatment of canine otitis externa.

Biofilm production by pathogens associated with canine otitis externa, and the antibiofilm activity of ionophores and antimicrobial adjuvants.

Otitis externa (OE) is a frequently reported disorder in dogs associated with secondary infections by Staphylococcus, Pseudomonas and yeast pathogens. The presence of biofilms may play an important role in the resistance of otic pathogens to antimicrobial agents. Biofilm production of twenty Staphylococcus pseudintermedius and twenty Pseudomonas aeruginosa canine otic isolates was determined quantitatively using a microtiter plate assay, and each isolate was classified as a strong, moderate, weak or nonbiofilm producer. Minimum biofilm eradication concentration (MBEC) of two ionophores (narasin and monensin) and three adjuvants (N-acetylcysteine (NAC), Tris-EDTA and disodium EDTA) were investigated spectrophotometrically (OD570nm ) and quantitatively (CFU/ml) against selected Staphylococcus and Pseudomonas biofilm cultures. Concurrently, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of planktonic cultures were assessed. 16/20 of the S. pseudintermedius clinical isolates were weak biofilm producers. 19/20 P. aeruginosa clinical isolates produced biofilms and were distributed almost equally as weak, moderate and strong biofilm producers. While significant antibiofilm activity was observed, no MBEC was achieved with narasin or monensin. The MBEC for NAC ranged from 5,000-10,000 µg/ml and from 20,000-80,000 µg/ml against S. pseudintermedius and P. aeruginosa, respectively. Tris-EDTA eradicated P. aeruginosa biofilms at concentrations ranging from 6,000/1,900 to 12,000/3,800 µg/ml. The MBEC was up to 16-fold and eightfold higher than the MIC/MBC of NAC and Tris-EDTA, respectively. Disodium EDTA reduced biofilm growth of both strains at concentrations of 470 µg/ml and higher. It can be concluded that biofilm production is common in pathogens associated with canine OE. NAC and Tris-EDTA are effective antibiofilm agents in vitro that could be considered for the treatment of biofilm-associated OE in dogs.

Perichondritis of the auricle: bacterial findings and clinical evaluation of different antibiotic regimens.

PURPOSE: Pseudomonas aeruginosa is commonly found in suppurative perichondritis, but the significant pathogens in non-abscess perichondritis are unclarified. We aimed to explore the bacterial findings and evaluate the effectiveness of different antibiotic regimes in the treatment of patients with perichondritis. METHODS: All patients treated for perichondritis at the two Ear-Nose-Throat Departments in Central Denmark Region (covering 20% of the Danish population) from January 1990 to October 2018 were included. RESULTS: In total, 112 patients with (n = 12) or without (n = 100) abscess were included in the study. Potential pathogens were found in 40 of 55 cultures. P. aeruginosa was recovered in 58% of abscess cases, while Staphylococcus aureus was predominant in non-abscess infections (49%). Eighty-two percent of S. aureus recovered were isolated as heavy or moderate growth. In non-abscess cases, no significant differences in clinical progress (p = 0.65), alteration in antibiotic therapy (p = 0.31), duration of hospitalization (p = 0.65), or frequency of relapse of infection (p = 1.00) or sequelae (p = 0.38) were found between patients treated with antibiotics covering S. aureus vs. P. aeruginosa. CONCLUSIONS: Our findings suggest that intravenous antibiotic therapy covering S. aureus is sufficient and appropriate empirical treatment in the majority of patients with non-abscess perichondritis. Antibiotic coverage should be expanded to include P. aeruginosa if the clinical response is disappointing or cultures grow P. aeruginosa. The risks and downsides to this approach seems limited as only a minority of patients suffered (minor) cosmetic sequelae and relapse of infection in our cohort of non-abscess perichondritis patients initially treated with antibiotics not covering P. aeruginosa.