Fungal malignant external otitis
Introduction
Malignant external otitis (MEO), also known as necrotizing external otitis, is an aggressive and potentially fatal infection that originates in the external ear canal and spreads progressively along the soft tissues and bone of the skull base, ultimately involving intracranial structures.1 This rare disorder occurs almost exclusively in elderly and diabetic patients.1, 2
Since Chandler’s publication of the first comprehensive case series of MEO in 1968,1 the most commonly reported causative pathogen has been Pseudomonas aeruginosa (>98% of cases).3 Other pathogens include Staphylococcus aureus,4 Staphylococcus epidermidis,5 Proteus mirabilis,6 and Klebsiella oxytoca.7 Fungi are rarely involved in MEO, and have been identified particularly in immune-compromised nondiabetic patients, such as patients with AIDS or acute leukemia.2, 8 Aspergillus fumigates is the most common cause of fungal MEO.8, 9
The traditional and well-accepted treatment for MEO is prolonged anti-pseudomonal therapy for at least 6 weeks as well as local treatment with lavage and eardrops. When cure is not achieved after 6 weeks, the antibiotic treatment is continued and other treatment modalities are considered, such as surgery for debridement10, 11, 12, 13 and hyperbaric oxygen chamber.14, 15, 16
Only few studies have focused on fungal MEO, and most of them are case reports. In a previous study by our group of severe MEO,11 cultures of specimens from the external canal were positive for fungi in almost half the patients with a persistent course. The aim of the present study was to describe patients with fungal infection and to further investigate the clinical characteristics and outcome of fungal MEO compared to nonfungal MEO.
The database of the department of otorhinolaryngology of a tertiary, university-affiliated medical center was searched for all patients hospitalized with MEO between 1990 and 2008. The diagnosis of MEO was based on the following criteria:
- 1.
External otitis not responsive to outpatient treatment of at least one week.
- 2.
Clinical findings of severe otalgia, edema, and exudates of the external ear canal, and/or granulation tissue at the external ear canal.
- 3.
Positive findings on bone scan (technetium with or without gallium).
- 4.
Histological exclusion of other causes of external otitis, such as tumors and cholesteatoma.
- 5.
Microabscess on pathology specimens obtained at surgery, if performed.
In addition, MEO was diagnosed when one criterion was not fulfilled but the disease failed to improve after one week of intravenous antibiotics and extensive local treatment.
Our treatment protocol for MEO consisted of intravenous ceftazidime, local eardrops, and daily ear lavage. Patients in whom the disease improved within 2 weeks were discharged and instructed to complete 6 weeks of treatment with oral ciprofloxacin or intravenous ceftazidime at home, administered by the home-care unit. Those who did not improve remained in hospital, and their antibiotic treatment was readjusted according to the culture results. In those who failed to respond to antibiotic treatment after 4 weeks, surgical debridement or hyperbaric chamber treatment was considered, according to the clinical and radiological findings. A persistent infection was defined as failure to improve after 2 full courses of systemic antibiotic treatment (>3 months).
Hyperbaric treatment, when considered necessary, was administered according to the Marx protocol,17 consisting of multiple once-daily sessions of breathing 100% oxygen under 2 ATA in a multi-seat hyperbaric chamber. Each session was divided into 3 equal periods of 30 min, with a 10-min interval before and after each period for pressure compression and decompression, respectively, with air breathing.
In our institution, ear tissue samples from patients with MEO are routinely cultured for both bacteria and fungi. In our patients with negative cultures who had an ongoing active disease, ear tissue samples were analyzed by panbacterial and panfungal 16sRNA polymerase chain reaction (PCR). Those with positive microbiological findings of fungal infection received antifungal treatment. Cure was defined as complete clinical resolution of symptoms and a negative gallium scan.
For purposes of the study, the patients’ medical records were reviewed for medical background, clinical characteristics, culture and imaging findings, management, and outcome. Findings were compared between patients with fungal and nonfungal MEO.
Continuous variables are given as mean ± standard deviation. Differences in mean age between groups were analyzed with the Mann–Whitney U test. To analyze statistically significant differences in the distribution of the categorical variables between the two groups, chi-square or Fisher exact test was performed, as appropriate. Survival was calculated from the date of diagnosis to the date of death or last follow-up using the Kaplan–Meier method; log-rank test was applied to compare survival curves between groups. P values less than or equal to 0.05 were considered statistically significant. For statistical analyses, we used SPSS 15.0.1 software (SPSS Inc., Chicago, IL, USA).
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Results
A total of 60 patients (39 male and 21 female) were diagnosed with MEO during the study period, of which 9 (15%) had a fungal infection. The characteristics of the patients with fungal and nonfungal disease are summarized in Table 1.
Discussion
To the best of our knowledge, this is the first case series of fungal MEO reported in the English literature. As part of our department’s wide experience with MEO,10, 18 we have observed that some patients have a persistent disease course (defined as >3 months of systemic antibiotic treatment), and that among this subgroup, the prevalence of fungal infection is relatively high (57%).
In the present study of 9 patients diagnosed with fungal MEO over an 18-year period, we found that fungal culture
Conclusion
Fungal MEO probably occurs secondary to prolonged antibiotic treatment in patients with primary bacterial MEO. Although fungal MEO is more invasive than bacterial MEO, as evidenced by imaging studies, the higher prevalence of facial nerve palsy, the greater need for surgical procedures, and the prolonged persistent course, there is no difference between the two infections in patient survival.
Since the outcome of fungal MEO is grim, aggressive treatment should be offered as early as possible.
Funding
No funding was received for this study.
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