Malignant otitis externa: Evolving pathogens and implications for diagnosis and treatment

Objective. Malignant otitis externa (MOE) is an invasive infection of the temporal bone that is classically caused by Pseudomonas aeruginosa. Increasingly, however, nonpseudomonal cases are being reported. The goal of this study was to evaluate and compare the clinical presentation and outcomes of cases of MOE caused by Pseudomonas versus non-Pseudomonas organisms.

Study Design. Retrospective case series with chart review.

Setting. Tertiary care institution.

Subjects and Methods. Adult patients with diagnoses of MOE between 1995 and 2012 were identified. Charts were reviewed for history, clinical presentation, laboratory data, treatment, and outcomes.

Results. Twenty patients diagnosed with and treated for MOE at the University of Pittsburgh Medical Center between 1995 and 2012 were identified. Nine patients (45%) had cultures that grew P aeruginosa. Three patients (15%) had cultures that grew methicillin-resistant Staphylococcus aureus (MRSA). Signs and symptoms at presentation were similar across groups. However, all of the patients with Pseudomonas had diabetes, compared with 33% of MRSA-infected patients (P = .046) and 55% of all non-Pseudomonas-infected patients (P = .04). Patients infected with MRSA were treated for an average total of 4.7 more weeks of antibiotic therapy than Pseudomonasinfected patients (P = .10). Overall, patients with non- Pseudomonas infections were treated for a total of 2.4 more weeks than Pseudomonas-infected patients (P = .25).

Conclusions. A high index of suspicion for nonpseudomonal organisms should be maintained in patients with signs and symptoms of MOE, especially in those without diabetes. MRSA is an increasingly implicated organism in MOE.