A Case of Fungal Ball Caused by Aspergillus oryzae in a Sake Brewery Worker

This is one of the rare, documented cases of non-invasive fungal sinusitis caused by <i>Aspergillus oryzae</i> in an immunocompetent worker exposed occupationally. A 34-year-old woman working at a <i>n</i> <i>ihon-shu</i> (rice wine or sake) brewery presented to our hospital with a headache. The patient was diagnosed with a fungal ball and underwent endoscopic sinus surgery. As the condition was non-invasive, the patient recovered with surgery alone and did not require antifungal treatment. Although fungal growth was not observed in a sinus pus culture, a histopathological examination of the removed sinus tissue revealed <i>Aspergillus</i>-like hyphae. <i>A. oryzae</i> is widely used in the brewing of <i>nihon-shu</i>. A genetic analysis of the rRNA, β-tubulin, and aflatoxin-related genes identified the organism as <i>A. oryzae</i>. The patient also provided a sample of the <i>koji</i> (malted rice) routinely used in her workplace. The <i>koji</i> was cultured and analyzed, and the genetic sequences in all three regions were found to have a 100% match with the clinical specimen, strongly suggesting it as the source of infection. Furthermore, this strain was susceptible to antifungal agents. Although <i>A. oryzae</i> is usually considered non-pathogenic to immunocompetent humans, it should be considered as a possible causative organism in workers involved in sake brewing and related fermentation industries.