Necrotising otitis externa (NOE) often does not yield identification of a causative organism to treat although in 90% of cases it is a member of the pseudomonas species. The incidence of fungal NOE is not to be forgotten and this group from Israel looked at cases of refractory NOE who had been initially treated with ciprofloxacin and did not respond. In a six year period, 19 patients were diagnosed with NOE of which five had negative microbiology cultures for causative organisms. Patients were taken to theatre and deep biopsies for histology and culture were obtained. PCR analysis testing was undertaken for a range of bacteria and fungi. All five cases had likely causative fungi isolated on PCR although sensitivities were not possible as fungi and bacterial cultures were negative.

Empirical antifungal treatment (directed by local microbiology knowledge), was started while anti-bacterials were halted. All patients clinically and radiologically improved and were discharged home on average after 39 days. Systemic treatment was for a total of eight weeks. Gallium scan, blood tests and clinical follow-up proved complete cure.

Had it not been for the PCR tests, continued treatment with anti-pseudomonals would have continued with further deterioration. Other methods of diagnosing fungal infection were not used and often required skilled personnel. PCR testing is expensive but can test for several fungi in a short space of time without expert mycologists. Your hospital laboratory may be able to perform this PCR with the kit they already have for your next case of refractory NOE. 

Clinical utility of a polymerase chain reaction assay in culture-negative necrotizing otitis externa.
Gruber M, Roitman A, Doweck I, et al.
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Anand Kasbekar

BMedSci, DOHNS, FRCS (ORL-HNS), DM, Nottingham University Hospitals NHS Trust; Associate, The University of Nottingham; Otology and Hearing Group, Division of Clinical Neuroscience, School of Medicine, University of Nottingham, UK.

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