title: Sterilization of liquid nitrogen with ultraviolet irradiation for safe vitrification of human oocytes or embryos.
abstract: 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."
authors: Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy. Electronic address: l.parmegiani@gynepro.it.
authors: Lodovico
authors: L
authors: Parmegiani
authors: Department of Occupational Medicine, University of Bologna, Bologna, Italy.
authors: Antonio
authors: A
authors: Accorsi
authors: Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
authors: Graciela Estela
authors: GE
authors: Cognigni
authors: Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
authors: Silvia
authors: S
authors: Bernardi
authors: Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
authors: Enzo
authors: E
authors: Troilo
authors: Reproductive Medicine Unit, GynePro Medical Centers, Bologna, Italy.
authors: Marco
authors: M
authors: Filicori
mesh_terms: 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
chemical_list: D009584:Nitrogen