Rhizomucor

Rhizomucor is a genus of mold fungi in the family Mucoraceae, order Mucorales. Species of Rhizomucor are common environmental saprotrophs found in soil, decaying vegetation, manure, and various foods. The genus includes several species, notably Rhizomucor pusillus and Rhizomucor miehei, the latter of which has been used industrially to produce microbial chymosin (rennet) for cheese making.

Several Rhizomucor species are opportunistic pathogens in humans, causing mucormycosis in immunocompromised individuals. Infection typically occurs after spore inhalation, ingestion, or traumatic implantation and can affect the sinuses, lungs, skin, or brain. The disease progresses rapidly and carries a high mortality rate despite treatment. Risk factors include diabetic ketoacidosis, neutropenia, solid organ or hematopoietic stem cell transplantation, corticosteroid therapy, and iron overload.

Diagnosis relies on microscopy and culture of specimens, with histopathology showing broad, non-septate or sparsely septate hyphae with wide-angle branching, and culture yielding fluffy cottony colonies. Molecular methods and MALDI-TOF can aid species-level identification. Management requires prompt antifungal therapy with liposomal amphotericin B, reversal of underlying risk factors, and surgical debridement when feasible. Step-down to posaconazole or isavuconazole may be considered in some cases, but efficacy varies and monitoring for drug interactions and toxicity is important. Rhizomucor species remain important targets in both clinical mycology and industrial applications.