Sterilization of liquid nitrogen with ultraviolet irradiation for safe vitrification of human oocytes or embryos.
OBJECTIVE
To evaluate the efficacy of ultraviolet (UV) irradiation for rapid microbial decontamination of liquid nitrogen (LN2).


METHODS
Basic research.


METHODS
Private assisted reproduction center.


METHODS
Microorganisms (bacteria and fungi).


METHODS
Two stainless steel open dewars containing LN2 were contaminated in a two-step experiment with high titers of cultures of bacteria (Stenotrophomonas maltophilia, Pseudomonas aeruginosa, and Escherichia coli) and fungi (Aspergillus niger). One of the two dewars was subsequently exposed to UV irradiation at 253.7 nm to obtain a rapid microbial decontamination before the complete evaporation of LN2.


METHODS
Detection of the micro-organisms in LN2 after UV sterilization through the assessment of bacterial and fungal growth in minimal and selective Petri dishes.


RESULTS
None of the contaminating micro-organisms were detected in LN2 after UV sterilization.


CONCLUSIONS
Decontamination of LN2 with UV irradiation is feasible and straightforward. The fact that LN2 can be quickly and safely sterilized should encourage the wider application of human oocyte and embryo vitrification with "open carriers."
Parmegiani
Lodovico
L
Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy. Electronic address: l.parmegiani@gynepro.it.
Accorsi
Antonio
A
Department of Occupational Medicine, University of Bologna, Bologna, Italy.
Cognigni
Graciela Estela
GE
Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
Bernardi
Silvia
S
Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
Troilo
Enzo
E
Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
Filicori
Marco
M
Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
D001234:Aspergillus niger / Q000166:cytology; D015169:Colony Count, Microbial; D015925:Cryopreservation / Q000379:methods; D004203:Disinfection / Q000379:methods; D004622:Embryo, Mammalian; D004926:Escherichia coli / Q000166:cytology; D005260:Female; D006801:Humans; D009584:Nitrogen / Q000528:radiation effects; D009865:Oocytes; D011550:Pseudomonas aeruginosa / Q000166:cytology; D012449:Safety; D020615:Stenotrophomonas maltophilia / Q000166:cytology; D013242:Sterilization / Q000379:methods*; D014466:Ultraviolet Rays / Q000009:adverse effects
D009584:Nitrogen