The Molecular Identification and Antifungal Susceptibilities of Aspergillus Species Causing Otomycosis in Tochigi, Japan
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Aspergillus species are the most common pathogenic fungi involved in otomycosis, an infection of the outer ear canal. In this study, we examined the incidence of Aspergillus infections and the antifungal susceptibilities of 30 Aspergillus species isolates from patients with otomycosis who visited Saiseikai Utsunomiya Hospital between August 2013 and July 2016. Based on the morphological test results, the strains were identified as Aspergillus niger sensu lato (20 strains), A. terreus sensu lato (7 strains), and A. fumigatus sensu lato (3 strains). In contrast, the molecular identifications based on analyzing the isolates’ partial β-tubulin gene sequences revealed them to be A. niger sensu stricto (12 strains), A. tubingensis (8 strains), A. terreus sensu stricto (7 strains), and A. fumigatus sensu stricto (3 strains). The antifungal susceptibility test results indicated that strains of A. tubingensis and A. niger sensu stricto displayed lower susceptibilities to ravuconazole, compared with the other isolates. The Aspergillus strains from this study showed low minimum inhibitory concentrations toward the azole-based drugs efinaconazole, lanoconazole, and luliconazole. Therefore, these topical therapeutic agents may be effective for the treatment of otomycosis.
KeywordsOtomycosis Aspergillus species Molecular identification Cryptic species Antifungal susceptibility testing
We would like to thank our colleagues in our laboratory at Saiseikai Utsunomiya Hospital for their help with this study. We thank Ms. Yoshiko Umeda, Laboratory Space and Environmental Medicine, Teikyo University, for technical assistance. We also thank Lesley Benyon, Ph.D., and Sandra Cheesman, Ph.D., from Edanz Group (www.edanzediting.com/ac) for editing a draft of this manuscript. This research was partially supported by the Research Program on Emerging and Re-emerging Infectious Diseases from the Japan Agency for Medical Research and development, AMED under Grant Number JP18fk0108008.
Compliance with Ethical Standards
Conflict of interest
The authors alone are responsible for the content of the paper and declare that they have no conflicts of interest to declare.
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