Liquid nitrogen (LN) used for cryostorage in sperm, oocyte and embryo banking can become contaminated by exposure to environmental agents. Sterility of LN sediment of 20 sperm and 7 cryopreservation oocyte-embryo containers were evaluated in this study. The years in operation and the number of stored samples were considered for each container. Standard microbiological procedures were used for bacteria and fungal detection. Presence of hepatitis B, hepatitis C, and human immunodeficiency viruses was evaluated by nucleic acid amplification techniques. No fungi or viruses were detected in any LN sediment samples tested at the sperm and oocyte-embryo banks. Five out 20 sperm containers, which had been used over 25 years, were contaminated by Bacillus megaterium, Bacillus circulans and Sphingomonas paucimobilis. Environmental bacteria like Bacillus spp. was found in one of the 7 oocyte-embryos bank containers. The number of stored samples was not related to the sort of pollution observed. LN manipulations during the vitrification process and its exposure to air in the room would be responsible for the bacterial contamination at the oocyte-embryo banks. Our results emphasize the importance of periodic cleaning of cryostorage containers as well as periodic chemical sterilization, mainly in cryostorage containers used over a large period of time.
Buy this Article