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Evaluation of Microsporum canis in different methods of storage
R S N Brilhante1, C S P Cavalcante, F A Soares-Júnior
1School of Veterinary Medicine, Post-Graduation Program in Veterinary Science, State University of Ceará, Fortaleza, Brazil. samiamic@yahoo.com.br
Abstract:
The main objective of this investigation was to evaluate different methods of storage for Microsporum canis based on materials and equipment that are readily available in developing countries. We tested 32 strains of M. canis at - 20 degrees C in potato dextrose agar (PDA) in its plain condition, or amended with 10% dimethyl sulfoxide or with 10% glycerol. In addition, we tested 25 degrees C storage of isolates in plain saline (0.9% NaCl) and in saline covered with a mineral-oil layer. After 9 months of storage, none of the M. canis strains frozen in PDA supplemented with glycerol survived, while only 16 and 6%, respectively, of the isolates in plain and DMSO medium lost viability. Nine month's storage in saline with or without mineral oil increased the amount of pleomorphic development of sterile hyphae; this phenomenon occurred at a significantly higher level than was seen in isolates stored at -20 degrees C. The physiological characteristics of M. canis were not affected by the different storage tests. The results suggest that, in order to ensure optimal viability, purity and pristine isolate condition, each M. canis isolate maintained should be held in at least two methods of storage, namely, PDA at -20 degrees C and saline with a mineral-oil layer at 25 degrees C.
Insights
For optimal Microsporum canis storage in developing countries, avoid glycerol at -20°C. Combining potato dextrose agar at -20°C with saline and mineral oil at 25°C best preserves fungal viability and purity.
Area of Science:
- Mycology
- Microbiology
- Fungal Strain Preservation
Background:
- Microsporum canis is a significant dermatophyte.
- Effective and accessible storage methods are crucial for maintaining fungal cultures, especially in resource-limited settings.
- Previous studies have explored various preservation techniques with varying success rates.
Purpose of the Study:
- To evaluate accessible storage methods for Microsporum canis in developing countries.
- To determine the optimal conditions for long-term viability and purity of M. canis isolates.
- To compare the efficacy of different storage media and temperatures.
Main Methods:
- Tested 32 M. canis strains under various storage conditions.
- Evaluated storage at -20°C in potato dextrose agar (PDA) with or without dimethyl sulfoxide (DMSO) or glycerol.
- Assessed storage at 25°C in saline with or without a mineral-oil layer for 9 months.
Main Results:
- Glycerol-supplemented PDA at -20°C resulted in 100% M. canis mortality.
- Plain PDA and DMSO-supplemented PDA showed 16% and 6% viability loss, respectively.
- Storage in saline (with or without mineral oil) at 25°C led to increased pleomorphic development of sterile hyphae compared to -20°C storage.
Conclusions:
- No single storage method guarantees optimal viability, purity, and condition of M. canis.
- A dual storage approach is recommended: PDA at -20°C and saline with a mineral-oil layer at 25°C.
- These methods offer a balance of accessibility and effectiveness for preserving M. canis in resource-limited environments.
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