In vitro study of antifungal effects of earthworm coelomic fluid obtained from Eisenia fetida on three opportunistic fungal pathogens.

Abstract

Background and purpose: Pathogenic fungi, including both true and opportunistic pathogens, pose significant health risks, particularly in immunocompromised individuals. Species, such as Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans, cause fatal infections and frequently develop resistance to conventional antifungal therapies. Limitations of current antifungal medications, such as drug toxicity, resistance development, and environmental concerns, highlight the urgent need for novel therapeutic strategies. Earthworm extracts, particularly those derived from Eisenia fetida, have been recognized as a promising alternative in traditional Chinese medicine. This study aimed to assess the antifungal effects of a peptide extract from E. fetida against these opportunistic fungal pathogens.

Materials and methods: The earthworm extract was obtained from E. fetida through electroporation and centrifugation to isolate bioactive components. Composition of the extract was analyzed in detail; accordingly, protein content was determined using the Bradford and Kjeldahl methods, fat content was measured via Soxhlet extraction, and moisture, dry matter, and ash contents were also quantified to provide a comprehensive profile. To evaluate antifungal activity, fungal cultures of A. fumigatus, C. albicans, and C. neoformans were grown on Sabouraud dextrose agar. The disk diffusion method was used to assess antifungal activity by measuring inhibition zones surrounding extract-containing disks. A dilution series of the E. fetida extract was also prepared to further analyze antifungal effects. The broth microdilution method was employed to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) for each fungal species, providing quantitative data on the effectiveness of the extract.

Results: The coelomic fluid extracted from E. fetida contained 60.03% protein, 8.136% fat, 6.91% ash, 6.03% moisture, and 8.65% dry matter. Disk diffusion assays revealed significant inhibition of A. fumigatus and C. albicans, with the extract exhibiting stronger effects at higher concentrations. In broth microdilution assays, the extract achieved MIC/MFC values of 12.5%/25% against A. fumigatus and 3.125%/6.25% against Candida albicans. However, its efficacy against C. neoformans was lower, while the commercial antifungal drug, itraconazole, demonstrated superior efficacy against all tested strains.

Conclusion: Earthworm extracts, rich in antimicrobial peptides, exhibit promising antifungal properties, particularly against C. albicans. Although not as effective as itraconazole, the potential of the extract as a safer and environmentally friendly alternative underscores its significance in antifungal research. Further studies are needed to enhance its efficacy and broaden its antifungal spectrum, potentially leading to new, sustainable strategies for managing fungal infections.