Lessons learnt from the diagnosis and antimicrobial management of necrotising (malignant) otitis externa: our experience in a tertiary referral centre. Necrotising otitis externa is an uncommon and aggressive infection of the external auditory canal with a tendency to present in the elderly and immunocompromised patient. We report a series of twenty-five patients admitted to our institution over a four-year period with this diagnosis. We review the diagnosis and antimicrobial management of these cases, and propose a treatment algorithm based on our experience.