Clinical and Mycologic Characteristics of Emerging Mucormycosis Agent Rhizopus homothallicus

Abstract

We retrospectively reviewed consecutive cases of mucormycosis reported from a tertiary-care center in India to determine the clinical and mycologic characteristics of emerging Rhizopus homothallicus fungus. The objectives were ascertaining the proportion of R. homothallicus infection and the 30-day mortality rate in rhino-orbital mucormycosis attributable to R. homothallicus compared with R. arrhizus. R. homothallicus accounted for 43 (6.8%) of the 631 cases of mucormycosis. R. homothallicus infection was independently associated with better survival (odds ratio [OR] 0.08 [95% CI 0.02–0.36]; p = 0.001) than for R. arrhizus infection (4/41 [9.8%] vs. 104/266 [39.1%]) after adjusting for age, intracranial involvement, and surgery. We also performed antifungal-susceptibility testing, which indicated a low range of MICs for R. homothallicus against the commonly used antifungals (amphotericin B [0.03–16], itraconazole [0.03–16], posaconazole [0.03–8], and isavuconazole [0.03–16]). 18S gene sequencing and amplified length polymorphism analysis revealed distinct clustering of R. homothallicus.

Keywords

• Rhizopus homothallicus
• Rhizopus arrhizus
• mucormycosis
• fungi
• fungal infections
• COVID-19 associated mucormycosis