Evaluation of purity, viability, stability and biochemical characteristics of clinical fungal isolates preserved by three different methods

Introduction: In era of organ transplants and immunocompromised patients, systemic mycosis has emerged as a major cause of morbidity and mortality among these patients. Research on these clinical fungal isolates is the key to the development of antifungal diagnostics and therapeutic agents. Mycology laboratories has to preserve these pathogenic fungal strains for various experiments. These laboratories requires a preservation method that ensures purity, viability, stability and biochemical characteristics of the fungal isolates during the storage period. Objectives: To determining the purity, viability, stability and biochemical characteristics of clinical fungal isolates subjected to three different, but simple and inexpensive preservation methods. Materials and Methods: A total of 50 clinical isolates of yeast and mold were subjected to different preservation Methods: All the isolates were evaluated for purity, viability, stability and biochemical characteristics before storage and after 6 months and one year. Stability testing was based on antifungal susceptibility testing as recommended by CLSI. Results: All the three preservation methods, ensured survival of all the fungal strains for one year duration. Periodic subculture method on agar slope demonstrated mild colony morphological changes in 2 molds and high contamination rate. Water culture technique and oil overlay technique, demonstrated protection of purity, viability, stability and biochemical characteristics of all the fungal isolates up to one year of storage. Conclusion: Comparison of different fungal storage methods suggested that both water technique and oil overlay technique can be utilized as a simple, effective and inexpensive methods for long term preservation of clinical fungal isolates.