AN IMPROVED METHOD FOR THE LONG-TERM PRESERVATION OF NAEGLERIA-GRUBERI

A simple method for the cryopreservation of axenic strains of Naegleria gruberi has been developed, using non-specialized equipment and a three-step freezing protocol. Cells from trophozoite stage, log-phase, cultures were transferred to medium containing 5% (v/v) dimethyl sulphoxide (DMSO), then placed in a series of refrigerators; -29 degrees C (2h); -70 degrees C (2h); Liquid nitrogen -196 degrees C. Viability levels of >40% were achieved for all strains tested, and high viability levels were maintained on storage for 2 years under liquid nitrogen.