Malignant otitis externa: An assessment of emerging pathogens and the prognostic factors

Although the mortalities from malignant otitis externa (MOE) have greatly reduced, it is still a potentially fatal clinical condition. This study was undertaken to review the treatment outcomes and prognostic factors in MOE and to compare the behavioral pattern of cases caused by pseudomonas and non-pseudomonas organisms. A retrospective chart review of patients diagnosed with MOE in a tertiary institution over a 13 year period was conducted. Treatment outcome was divided into survival and mortalities groups. Demographic and disease factors were analyzed regarding mortalities using univariate and multivariate analysis. Seventeen of 22 cases were analysed. Nine (53%) were diabetic while 5 were HIV positive. After average of 7 weeks of antibiotic therapy ± surgical debridement, the disease resolved in 59%. Mortality was 41%. Diagnostic delay, poor blood sugar control, and extensive disease were found to predict mortality (P = 0.051, 0.048, and 0.006 respectively). Age, sex, causative organism, HIV infection, facial nerve and other cranial involvement did not significantly predict mortality. Pseudomonas aeruginosa was isolated in 11 patients. The rest had atypical organisms, Staphylococcus aureus and Proteus spp. There was no significant difference in the disease extension, mortality, duration of treatment and facial nerve involvement between pseudomonas and non-pseudomonas groups. However the pseudomonas group were predominantly diabetic (p = 0.03). It is concluded that malignant otitis externa still has a significant mortality despite aggressive therapy. Extensive temporal bone/intracranial disease, poor blood sugar control, and diagnostic delay portend a poorer prognosis. S. aureus is an increasingly important causative organism in MOE especially in non-diabetic patients.   Key words: Malignant otitis externa, mortality, risk factors, causative organisms.