A Head-to-head Comparison of Four Cryopreservation Protocols of Dermatophyte Species

Aims Transportation of clinical samples and long-term recoverability of fungal strains are critical to epidemiological studies. In addition, the study of fungi often requires the use of living pure cultures. The aim of this study was to evaluate the methods used to preserve culture collections of dermatophytes, consisted of storage in sterile distilled water, cryopreservation with glycerol, preserving in tryptic soy broth (TSB), and freezing mycobiotic agar. Materials & Methods In this experimental study, ninety-two dermatophyte isolates belonged to 10 species were tested. The freezing protocol was done in 4 forms of sterile distilled water, cryopreservation with glycerol, freezing mycobiotic agar, and preserving in TSB. The viability of the dermatophytes species was assessed after 3 years at morphological (macro and microscopic features), physiological (Using Dermatophyte Test Medium; DTM, urease test media, and the hair perforation test), and genetic levels by restriction fragment length polymorphism (RFLP). Findings The survival rate was 84 out of 92 water stored fungal strains (91.3%) and 81 out of 92 mycobiotic agar stored strains (88.0%) and 75 out of 92 glycerol 40% stored strains (81.5%) and 43 out of 92 TSB stored fungal strains (46.7%). Overall, more than 88% of the strains survived in the distilled water storage and freezing mycobiotic agar methods, while storage in TSB had the least success in the maintenance of dermatophytes. Conclusion The procedure to preserve cultures in sterile distilled water is reliable, simple, and inexpensive.

Keywords:

Dermatophytes , Cryopreservation , Polymerase Chain Reaction , Restriction Fragment Length Polymorphism