J Mycol Infect.  2023 Dec;28(4):121-122. 10.17966/JMI.2023.28.4.121.

Morphological Characteristics of Monascus ruber

• Kim J
• Sung GH
• Oh J
• Kim SY

• KMID: 2551443
• DOI: http://doi.org/10.17966/JMI.2023.28.4.121

Abstract

Monascus ruber (anamorph: Basipetospora rubra) is a filamentous Ascomycetous fungus (family: Monascaceae; order: Eurotiales) isolated from fermented foods and grain. In Asia, it is traditionally used to produce Monascus-fermented rice. It is commonly used as a natural food colorant (yellow-, orange-, and red-colored pigments), flavoring agent, and preservative for fish and meat ¹ . Until recently, only a few cases of M. ruber infection have been reported in elderly patients. These cases included invasive gastric infection postconsumption of contaminated dried and salted fish, renal infection post-surgery, and onychomycosis in diabetic individuals from French Guiana, India, and Morocco. Onychomycosis was successfully treated orally with terbinafine, but treatment for gastric infection with liposomal amphotericin B resulted in nephrotoxicity despite normal renal function at admission ^2,3 . Recently, M. ruber was isolated from a patient with chronic otitis media from Korea ³ . The 69-year-old male patient presented to the Otolaryngology Department, suffering from right-sided otorrhea for 1 year and reduced hearing for 7 years. Tympanoscopy of the right ear showed a near-perforation of the tympanic membrane with purulent discharge and fungal hyphae. A swab specimen from the discharge was cultured using Sabouraud's dextrose agar supplemented with chloramphenicol. After 7 days of incubation at 25℃, a flat, spreading mold with a thinly floccose texture and white to reddish color was evident (Figs. 1A, 1B). Microscopic examination revealed numerous round and thin-walled cleistothecia containing oval ascospores with smooth walls in lactophenol blue staining (Fig. 1C) and wet staining (Fig. 1D). The result of MALDI-TOF MS using tube extraction method showed no identification. The fungus was identified as M. ruber (synonym M. pilosus) through a polyphasic approach combining morphological characters and sequencing of the internal transcribed spacer regions, large subunit ribosomal ribonucleic acid, β-tubulin, and calmodulin encoding-genes. Endoscopic trans-canal myringoplasty was successfully performed on the patient, followed by a 6-week oral treatment with fluconazole.

Keyword

Cleistothecia; Monascus ruber; Natural pigments