Evaluation of plasma canine C-reactive protein concentrations in dogs with otitis media, healthy dogs and dogs with chronic otitis externa.

BACKGROUND: Otitis is characterised by inflammation of one or more of the structures of the ear. At present, to confirm or exclude otitis media (OM), it is most often necessary to perform a computed tomography (CT) scan or magnetic resonance imaging. Inflammation is an immune defence response found in many conditions that can be detected and tracked by measuring biological markers of inflammation as the Canine C-reactive protein (CRP). OBJECTIVES: The objective of this study was to determine whether CRP measurement is useful as an adjunctive diagnostic tool in dogs with otitis and whether elevated concentrations correlated with disease severity/presence of OM. ANIMALS: Twenty-four client-owned dogs were recruited over 1 year. MATERIALS AND METHODS: The dogs were divided into three groups: chronic or recurrent otitis externa (CO), otitis media (OM) and H (healthy). The dogs with otitis underwent a CT scan of the head, measurement of the plasma CRP concentration and evaluation of a 0-3 Otitis Index Score 3 (OTIS3 score). RESULTS: No dog (0%) in group H had an increased CRP value, compared to 20% in the CO group (one of five dogs) and 23% in the OM group (3 of 13 dogs). Plasma CRP concentrations show a statistically significant positive relationship with the OTIS3 score (p = 0.04). CONCLUSION AND CLINICAL RELEVANCE: Plasma CRP concentration is not reliable as a discriminatory tool in cases of otitis, although there is a trend for elevation in cases with more severe disease. However, a larger study may provide a statistically more reliable correlation between the severity of OM and CRP concentrations.

Prognosticating patients with necrotising otitis externa based on response to treatment.

INTRODUCTION: Necrotising otitis externa (NOE) is a severe infection of the temporal bone. The traditional severity based staging system does not fully prognosticate all patients with NOE. We hypothesise that a patient response staging system would more accurately capture the disease process and guide prognosis. METHODS: We carried out a retrospective notes review of patients diagnosed with NOE from January 2017 to December 2018 in a regional tertiary referral centre. Patient outcomes from our proposed patient response staging system were compared to a modified previously published severity based Gleeson staging system with patients requiring prolonged treatment classified as having a poor outcome. RESULTS: A total of 34 patients were treated for NOE. The majority were male (n=24) and had diabetes (n=25). Patients with the most severe Gleeson staging did not have the worst outcome. Daily delay in resolution of otorrhoea was associated with an increased need for more than six weeks of treatment. Rapid responders are patients who had resolution of otalgia, otorrhoea and C-reactive protein normalisation within 14 days, and all were cured following standard 6 weeks of treatment. CONCLUSIONS: The Gleeson staging system was valuable in assessing the extent of disease and all early Gleeson staged patients had good outcomes. However, patients with higher severity staging on the Gleeson system did not necessarily require prolonged treatment. There is a role for a joint approach in staging patients based on both modified Gleeson and treatment response, which would subsequently guide prognosis, duration of treatment and early diagnosis of potential fungal NOE.

Antibiotic plasma levels in dogs with otitis externa treated routinely with various topical preparations.

We aimed to determine whether, and at what levels, topical antibiotics applied to treat Otitis externa in dogs are absorbed systemically, leading to an increased risk of antibiotic resistance. 75 dogs brought to a veterinarian for Otitis externa were recruited for a non-interventional study. Selection criteria included diagnosis of Otitis externa and owner consent.The animals were divided into five groups of 15 dogs each. Each group received one of five commonly prescribed topical medications for up to 14 days according to the labeled instructions. Development and validation of low residue detection methods (HPLC-MS/MS) for all active substances studied was performed. Plasma concentrations were evaluated for gentamicin (Otomax, Easotic), marbofloxacin (Aurizon), orbifloxacin (Posatex) and polymyxin B (Surolan). Low-level plasma concentrations of the topically applied antibiotics were detected after multiple administrations. In several samples, the concentrations detected were less than the limit of detection (LOD) of the corresponding analytical method. However, at the end of the treatment period, mean plasma concentrations were in the low pmol/ml range and exceeded the LOD for gentamicin, marbofloxacin and orbifloxacin. None of the plasma samples examined for polymyxin showed levels above the LOD. After routine topical antibiotic use in the treatment of Otitis externa in dogs, low systemic plasma concentrations are likely to develop.This low-level exposure may facilitate cellular changes that lead to an increased possibility for antibiotic resistance. These findings should provoke veterinary clinicians to optimise therapy for Otitis externa in light of minimising the development of antibiotic resistance.

Blood group phenotype determines lectin-mediated adhesion of Pseudomonas aeruginosa to human outer ear canal epithelium.

Pseudomonas aeruginosa is the most frequent bacterial pathogen causing acute diffuse otitis externa. In a recent prospective phase II study we demonstrated that lectin-mediated bacterial adhesion can be blocked by receptor-analogue carbohydrates in patients suffering from Pseudomonas aeruginosa-induced acute otitis externa. In this investigation, human ABO blood group antigens were analysed on outer ear canal epithelial cells with standard routine histological procedures by monoclonal antibodies for the blood groups A and B, and with Ulex europaeus I lectin for the blood group O, respectively. In all cases (n = 20) the blood groups could be shown immunohistologically. P. aeruginosa-specific adhesion and inhibition assays were performed in the presence of N-acetylgalactosamine (GalNAc), N-acetylglucosamine (GlcNAc), D-mannose and A-like substance. Outer ear canal tissue sections were incubated with P. aeruginosa (strain PA 60), presenting lectin-specificity for GalNAc. Sections from patients presenting with blood group A were closely settled with bacteria in the presence of non-specific GlcNAc, D-mannose and PBS however, GalNAc and A-like substance inhibited the microbial adhesion. Amongst others, P. aeruginosa present adhesion molecules (lectins) with specificity for GalNAc. Thus, the correlation between blood group A phenotype and P. aeruginosa-induced acute diffuse otitis externa was investigated. Statistical evaluation proved a highly significant association. These data support the hypothesis that P. aeruginosa lectins with GalNAc specificity apparently adhere to GalNAc moieties, representing the terminal blood group A-determinant and further indicate that patients presenting with blood group A may have a genetic disposition for this form of otitis externa.

Malignant external otitis: utility of CT in diagnosis and follow-up.

Malignant external otitis is a severe bacterial infection of the bone and soft tissues of the base of the skull that is frequently difficult to diagnose. The effectiveness of antibiotic therapy is likewise difficult to assess. Serial computed tomographic (CT) scans were obtained in 11 consecutive patients with malignant external otitis at time of diagnosis and periodically after conclusion of antibiotic therapy. All patients demonstrated abnormalities of the external auditory canal, with or without bone destruction. Soft tissue or fluid in the middle ear and mastoid, around the eustachian tube, and in the parapharyngeal space (both pre- and poststyloid) was seen in greater than 50% of the cases. While remineralization of bone was not seen, soft-tissue disease improved dramatically, and recurrence or persistence could be corroborated by detection of more extensive soft-tissue changes. By delineating the extra- and intracranial extent of disease, serial CT scans enable one to make the diagnosis, determine the extent of infection, document recurrence, exclude progression, and confirm resolution of malignant external otitis.