Case Report: The application of metagenomic next generation sequencing in diagnosing fungal malignant external otitis: a report of two cases

Malignant otitis externa is an invasive, potentially life-threatening infection of the external ear and skull base that requires urgent diagnosis and treatment. It affects immunocompromised individuals, particularly those who have diabetes. The most common causative agent remains Pseudomonas aeruginosa. Definitive diagnosis is frequently elusive, requiring a high index of suspicion, various laboratory and imaging modalities, and histologic exclusion of malignancy. Long-term oral antipseudomonal agents have proven effective; however, pseudomonal antibiotic resistance patterns have emerged and therefore other bacterial and fungal causative agents must be considered. Adjunctive therapies, such as aggressive debridement and hyperbaric oxygen therapy, are reserved for extensive or unresponsive cases.

Aspergillus and Candida spp are the most frequently isolated fungi in patients with otomycosis. The diagnosis of otitis externa relies on the patient's history, otoscopic examination under microscopic control, and imaging studies. Direct preparation of the specimens, particularly with optical brighteners, mycologic culture, and histologic examination, is very important and strongly recommended for the correct diagnosis. Patients with noninvasive fungal otitis externa should be treated with intense débridement and cleansing, and topical antifungals. Topical antifungals, such as clotrimazole, miconazole, bifonazole, ciclopiroxolamine, and tolnaftate, are potentially safe choices for the treatment of otomycosis, especially in patients with a perforated eardrum. The oral triazole drugs, itraconazole, voriconazole, and posaconazole are effective against Candida and Aspergillus, with good penetration of bone and the central nervous system. These drugs are essential in the treatment of patients with malignant fungal otitis externa complicated by mastoiditis and meningitis. Copyright 2010 Elsevier Inc. All rights reserved.

Invasive otitis externa (IOE) due to Aspergillus is a rare, potentially life-threatening, invasive fungal infection affecting immunocompromised patients. The invasive process may lead to skull base osteomyelitis with progressive cranial nerve palsies and can result in irreversible hearing and neurological impairment. We report two cases of Aspergillus IOE treated with voriconazole alone and a literature review of antifungal therapy of Aspergillus IOE. Twenty-five patients, including the two described in the present report, were analyzed. Eighteen patients were treated with amphotericin B, and nine of them received itraconazole as an additional agent. Three patients received initial therapy with itraconazole, and one patient was treated with both voriconazole and caspofungin therapy. The two patients in the present report received voriconazole therapy alone with good clinical and biological tolerance despite prolonged treatment. The last patient did not receive antifungal therapy, as the diagnosis was made postmortem. Eighteen patients underwent an initial extensive surgical debridement. The majority of the patients had a favorable outcome, 17 patients experienced a complete recovery, and 6 showed a partial improvement. Both of the patients reported on here had favorable outcomes, and no aggressive surgical debridement was required. Although voriconazole has been shown to be effective for the treatment of invasive aspergillosis, its precise role in the management of Aspergillus IOE had not been documented. These observations demonstrate that voriconazole could be an effective and well-tolerated therapeutic option for the management of Aspergillus IOE.