Risk of Contamination of Gametes and Embryos during Cryopreservation and Measures to Prevent Cross-Contamination

Abstract

The introduction and widespread application of vitrification are one of the most important achievements in human assisted reproduction techniques (ART) of the past decade despite controversy and unclarified issues, mostly related to concerns about disease transmission. Guidance documents published by US Food and Drug Administration, which focused on the safety of tissue/organ donations during Zika virus spread in 2016, as well as some reports of virus, bacteria, and fungi survival to cryogenic temperatures, highlighted the need for a review of the way how potentially infectious material is handled and stored in ART-related procedures. It was experimentally demonstrated that cross-contamination between liquid nitrogen (LN2) and embryos may occur when infectious agents are present in LN2 and oocytes/embryos are not protected by a hermetically sealed device. Thus, this review summarizes pertinent data and opinions regarding the potential hazard of infectious transmission through cryopreserved and banked reproductive cells and tissues in LN2. Special attention is given to the survival of pathogens in LN2, the risk of cross-contamination, vitrification methods, sterility of LN2, and the risks associated with the use of straws, cryovials, and storage dewars.

Experimental Evidence Reveals Both Cross-Infection and Cross-Contamination Risk of Embryo Storage in Liquid Nitrogen Biobanks

“…Nevertheless, closed vitrification devices do not prevent persistence of the embryo infection. Components in culture medium and cryoprotective additives may act as a stabiliser for microorganisms at cryogenic temperatures [13][14][15]. Many researchers have recognised that embryo collection procedures and cryopreservation protocols are not sterile techniques [4,6].…”

“…In the absence of securely sealed closed-device systems, there is a theoretical risk of microbial and viral cross-contamination between specimens commonly stored in liquid nitrogen [5,[10][11][12]. Liquid nitrogen presents significant risks in the transmission and propagation of diseases [13,14]. Components in culture and cryoprotective additives may act as a stabilizer or prevent cryoinjuries for microorganisms at cryogenic temperatures [5,14,15].…”

“…Liquid nitrogen presents significant risks in the transmission and propagation of diseases [13,14]. Components in culture and cryoprotective additives may act as a stabilizer or prevent cryoinjuries for microorganisms at cryogenic temperatures [5,14,15]. So, the risk of transfer of microorganisms from liquid nitrogen to stored gametes and embryos is notable.…”

Science of cryopreservation in reproductive medicine – Embryos and oocytes as exemplars

“…Standard straw is a system that can be used both open and closed, if it is in the middle of another straw ("Straw-in-straw"). It is believed that closed systems will avoid the contamination of reproductive material during exposure to liquid nitrogen [23].…”

Safe Storage of Gametes and Embryos: No Time for Complacency

“…Although the overall risk would appear low, the possibility remains that contaminants could be present should plastic cryopackaging become damaged, leak, or used in an "open" cryopreservation system as is often the case when embryos and oocytes are vitrified. 58,59 Open systems used in oocyte/embryo cooling and thawing continue to stimulate debate, particularly with regard to their relative biosafety. In a comprehensive review, Vajta et al described the surprising lack of any report of a crossinfection incident in RM despite the methods of gamete/ embryo processing and storage being largely aseptic.…”