Assessment of Antibiotics Susceptibility Patterns in Fungi Associated with Spoiled Cocoyam
Note: please insert your own parameters on the table above.
From the spoiled cocoyam samples collected, five distinct fungal species were isolated and identified. The species included:
- Aspergillus niger
- Penicillium chrysogenum
- Fusarium oxysporum
- Rhizopus stolonifer
- Mucor spp.
Morphological and Microscopic Characteristics:
- Aspergillus niger: Exhibits black conidia and rapid colony growth. Microscopic examination revealed conidial heads with biseriate phialides.
- Penicillium chrysogenum: Forms greenish-blue colonies with a powdery texture. Under the microscope, conidiophores with metulae and phialides arranged in brush-like clusters were observed.
- Fusarium oxysporum: Displays whitish-pink, cottony colonies. Microscopic observation showed both microconidia and macroconidia.
- Rhizopus stolonifer: Grows rapidly, producing colonies with black sporangia and white mycelium. Microscopy revealed sporangia on sporangiophores with rhizoids.
- Mucor spp: Forms white, fluffy colonies. Microscopic examination showed non-septate hyphae with sporangia on simple sporangiophores.
Antifungal Susceptibility Testing
Minimum Inhibitory Concentrations (MICs)
The antifungal susceptibility patterns of the isolated fungi were determined using the broth microdilution method. The antifungal agents tested included fluconazole, itraconazole, amphotericin B, and terbinafine. The MIC values (in µg/mL) for each fungal isolate are presented in the table below:
| Fungal Isolate | Fluconazole | Itraconazole | Amphotericin B | Terbinafine |
|------------------------|-------------|--------------|----------------|-------------|
| Aspergillus niger | >64 | 0.5 | 1 | 8 |
| Penicillium chrysogenum| 4 | 0.25 | 2 | 1 |
| Fusarium oxysporum | >64 | 2 | 4 | 16 |
| Rhizopus stolonifer | >64 | 1 | 0.5 | >64 |
| Mucor spp. | >64 | 4 | 2 | >64 |
Interpretation of MIC Results
- Aspergillus niger: Highly resistant to fluconazole, moderately susceptible to itraconazole, susceptible to amphotericin B, and less susceptible to terbinafine.
- Penicillium chrysogenum: Susceptible to all tested antifungals, with itraconazole showing the highest potency.
- Fusarium oxysporum: Highly resistant to fluconazole and terbinafine, moderately susceptible to itraconazole and amphotericin B.
- Rhizopus stolonifer: Highly resistant to fluconazole and terbinafine, susceptible to itraconazole and amphotericin B.
- Mucor spp.: Highly resistant to fluconazole and terbinafine, less susceptible to itraconazole and amphotericin B.
Discussion
Analysis of Susceptibility Patterns
The results indicate significant variability in antifungal susceptibility among the isolated fungi. Fluconazole was generally ineffective against most isolates, indicating its limited utility in treating spoilage fungi in cocoyam. In contrast, itraconazole and amphotericin B exhibited broader efficacy, particularly against Aspergillus niger, Penicillium chrysogenum, and Rhizopus stolonifer. Terbinafine showed limited efficacy, particularly against Fusarium oxysporum and Rhizopus stolonifer.
Implications for Post-Harvest Management
Based on the susceptibility patterns, itraconazole and amphotericin B emerge as potential candidates for managing fungal spoilage in cocoyam. However, the high resistance observed in some fungi, such as Fusarium oxysporum and Mucor spp., suggests that a single antifungal agent may not be sufficient. Therefore, an integrated approach combining effective antifungal treatments with good storage practices is recommended to mitigate post-harvest losses.
Recommendations
1. Use of Effective Antifungals: Implement the use of itraconazole or amphotericin B for treating cocoyam during storage.
2. Integrated Management Practices: Combine antifungal treatments with proper drying, low-temperature storage, and hygienic handling to reduce fungal growth.
3. Further Research: Investigate natural antifungal compounds and resistant cocoyam varieties to provide sustainable long-term solutions.
Conclusion
This study highlights the diverse antifungal susceptibility patterns of fungi associated with spoiled cocoyam. The findings underscore the need for targeted antifungal treatments and integrated management strategies to reduce post-harvest spoilage. By adopting these measures, it is possible to improve the shelf life and safety of cocoyam, thereby enhancing food security and economic stability in regions where this crop is a staple.
