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Antifungal effect of soil Bacillus bacteria on pathogenic species of the fungal genera Aspergillus and Trichophyton

Summary

Researchers discovered that four types of Bacillus bacteria found in soil can effectively kill dangerous fungi that cause infections in humans. These bacteria produce natural compounds that inhibit fungal growth even better than some standard antifungal medications. This discovery is particularly important because many fungi are becoming resistant to current drugs, making these soil bacteria a promising natural alternative for treating fungal infections.

Background

Fungal infections have increased rapidly, affecting 20-25% of the global population with 1.6 million fatalities annually. The widespread use of antifungal medications has contributed to emerging resistance, and existing treatments have limitations including toxicity and inadequate absorption. Soil microorganisms, particularly Bacillus species, are recognized as important sources of natural antimicrobial compounds.

Objective

To isolate and identify Bacillus species from soil samples with inhibitory effects on pathogenic Aspergillus and Trichophyton species, and to investigate the inhibition percentage of Bacillus metabolites compared to standard antifungal drugs.

Results

Fifteen of fifty soil samples showed antifungal effects, yielding 55 bacterial strains with 4 isolates showing strong activity identified as Bacillus subtilis, B. licheniformis, B. axarquiensis, and Bacillus sp. B. subtilis showed significantly higher inhibition percentages against all tested fungi compared to ketoconazole and amphotericin B, with growth inhibition ranging from 79.9% to 95.5% in liquid cultures.

Conclusion

Soil-derived Bacillus species demonstrated strong inhibitory effects against both Aspergillus and Trichophyton species, with B. subtilis showing the most promising antifungal activity. Further investigation is needed to identify specific metabolites responsible for antifungal activity and explore their mechanism of action and biocontrol potential.
  • Published in:Iran Journal of Microbiology,
  • Study Type:Experimental Laboratory Study,
  • Source: 10.18502/ijm.v17i2.18397
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