Mucor germinans, a novel dimorphic species resembling Paracoccidioides in a clinical sample: questions on ecological strategy

Summary

Researchers identified a new fungal species called Mucor germinans from a patient with Burkitt lymphoma that can switch between filamentous and yeast-like forms. This is unusual because Mucor species are typically identified by their thread-like filaments, not budding yeast cells. The yeast form appeared at body temperature and resembled a different fungus called Paracoccidioides, potentially causing misdiagnosis. The discovery emphasizes the importance of recognizing that some Mucor infections may present with yeast-like cells and highlights the need for rapid, accurate identification to guide appropriate antifungal treatment.

Background

Mucormycosis is a devastating opportunistic infection with high morbidity and mortality in immunocompromised patients. Mucoralean fungi are classically identified by non-septate hyphae in clinical samples. However, yeast-like forms have been rarely reported in Mucorales infections, potentially causing diagnostic confusion with other dimorphic fungi.

Objective

To identify and characterize a dimorphic mucoralean fungus isolated from sputum of a patient with Burkitt lymphoma that resembled Paracoccidioides. To investigate the temperature-dependent dimorphic properties and ecological significance of yeast formation in Mucor species.

Results

A novel dimorphic Mucor germinans species was identified from sputum showing multilateral budding cells resembling Paracoccidioides. Temperature, oxygen, and glucose concentrations drove dimorphic conversion to yeast-like cells. All three Mucor species studied contained multinucleate yeast cells, distinguishing them from mononuclear Candida and Cryptococcus species.

Conclusion

Mucor germinans represents a new dimorphic species capable of producing yeast-like forms at body temperature. Recognition of mucoralean yeast cells in clinical samples is critical to prevent diagnostic delay and misidentification with Paracoccidioides or other fungi. Multinucleate yeast cells serve as a diagnostic parameter to distinguish mucoralean infections from similar morphologies.
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