Monoclonal Antibodies Can Aid in the Culture-Based Detection and Differentiation of Mucorales Fungi—The Flesh-Eating Pathogens Apophysomyces and Saksenaea as an Exemplar

Summary

This research developed a special antibody test to quickly identify deadly flesh-eating fungi called Apophysomyces and Saksenaea, which cause serious skin and soft tissue infections. These fungi are difficult to identify because they don’t form spores on standard laboratory media. The new test uses a simple method combining antibody detection with a rapid lateral-flow test, similar to a COVID-19 test, making diagnosis faster and more reliable in hospitals that don’t have access to expensive equipment.

Background

Mucormycosis is a lethal angio-invasive disease caused by Mucorales fungi, with Apophysomyces and Saksenaea species responsible for the majority of cutaneous and soft tissue necrotizing infections. These pathogens are notorious for their failure to sporulate on standard mycological media, complicating identification and delaying appropriate treatment. Prompt detection and differentiation from Aspergillus fumigatus is critical due to differing sensitivities to antifungal drugs.

Objective

To develop and evaluate a monoclonal antibody (mAb JD4) specific to Apophysomyces species for culture-based detection and differentiation of non-sporulating Mucorales pathogens. The study aimed to create a simple diagnostic method that could be implemented in low- and middle-income countries lacking access to sophisticated diagnostic technologies.

Results

mAb JD4 demonstrated genus-specific binding to a 15 kDa heat-labile protein present in all Apophysomyces species tested but absent in Saksenaea and Aspergillus fumigatus. The lateral-flow immunoassay successfully differentiated Mucorales species from A. fumigatus using simple swab extracts from 24-hour cultures. Combined use of the LFIA and mAb JD4-based ELISA enabled rapid differentiation of Apophysomyces from Saksenaea species.

Conclusion

Monoclonal antibody JD4 enables rapid detection and differentiation of Apophysomyces species from other fungal pathogens causing cutaneous and soft tissue mycoses. When combined with a rapid lateral-flow immunoassay, this approach offers improved sensitivity and specificity for Mucorales detection based on culture, representing a practical diagnostic solution for resource-limited settings.
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