Dissolving the glue in glue ear: Assessment of the efficacy of the use of Dornase alfa as an adjunct therapy to ventilation tube insertion.

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Bacteria in biofilm contributes to the persistence and recurrence of infection within the middle ear. Our preliminary data shows that as well as biofilm being present on the surface of the middle ear mucosa, bacterial biofilms are also present within extensive DNA scaffolding in the viscous middle ear effusion (MEE). We have demonstrated otopathogenic bacteria both in biofilm microcolonies and singularly throughout DNA strands within 92% of MEEs tested. The DNA appears to be mainly neutrophil derived and is largely produced via an active immune mechanism known as neutrophil extracellular traps (NETs). The extensive DNA stranding and the involvement of biofilm microcolonies is similar to what is observed in broncho-alveolar lavage fluids from children with cystic fibrosis (CF). This DNA increases the viscosity of the sputum in the lung and it is within this viscous fluid that bacterial biofilm aggregates exist. Sputum viscosity is targeted in CF through the use of a recombinant human deoxyribonuclease I (Dornase alfa or Pulmozyme®). Dornase alfa acts to selectively cleave DNA which reduces fluid viscosity and allows bacterial clearance from the lung. We propose that administration of Dornase alfa to the middle ear at time of VTI may help to reduce the viscosity of the MEE and thereby permit clearance of the bacteria that are the cause of recurring ear infections. Our preliminary in vitro studies have demonstrated that Dornase alfa successfully dissociates the DNA scaffolding in MEE from children with OM. Dornase alfa is used extensively in the treatment of CF in adults and in children and has been proven both safe and efficacious in humans when administered by inhalation via a nebuliser. These patients are often administered with 2.5ml of a 1mg/ml solution of the enzyme twice daily. Furthermore, Dornase alfa has been tested in a chinchilla model, testing for toxicity to cochlear outer hair cells and any changes in the auditory brain response following application to the round window. These studies determined that Dornase alfa is non-ototoxic when administered into the middle ear of chinchillas. This group has subsequently gone on to conduct a clinical trial investigating the use of Dornase alfa to unblock clogged ventilation tubes (VTs) in children (ClinicalTrials.gov identifier: NCT00419380). The aim of this study is to evaluate whether Dornase alfa treatment at the time of ventilation tube insertion (VTI) will break down the DNA scaffold and the associated biofilms in the MEE improving bacterial clearance from the middle ear. We believe this will reduce the recurrence of infection and reduce the number of repeat VTIs.