title: Microbial contamination of cord blood stem cells.
abstract: OBJECTIVE
  After storage, low levels of contaminating bacteria in standard blood components can reach bacteraemic levels, causing severe transfusion-associated sepsis. For cord blood (CB), the significance of low levels of contaminating bacteria and the optimal detection method is unknown and not supported by available guidelines.
  
  
  METHODS
  Spiking experiments and testing of various subfractions of CB units were used to determine the behaviour of bacteria during centrifugation, freezing and thawing. For routine testing of CB, different volumes were compared for the detection of potential pathogens and micro-organisms of low pathogenicity.
  
  
  RESULTS
  Centrifugation, as applied to CB fractionation, does not show concentration of bacteria in any particular fraction and supports the possibility of culture of waste fractions. Dimethylsulphoxide (DMSO) and freezing does not affect the viability of bacteria under the conditions used in this study. Owing to the low contamination level, a large sample volume of 20 ml was more sensitive than a 10-ml sample volume. Eighty five per cent of the isolated strains can be considered to be of low pathogenicity.
  
  
  CONCLUSIONS
  When an optimal waste fraction sample volume of 20 ml was cultured, the contamination rate of CB was found to be approximately 13%, with low levels of < 1 colony-forming unit (CFU)/ml. Such levels of bacteria of low pathogenicity are expected to be of clinical importance only when CB is expanded in vitro for a prolonged period of time.
authors.affiliation: Sanquin Blood Supply Foundation, Blood Bank Leiden-Haaglanden, Leiden, The Netherlands. aine.honohan@sanquinbblh.nl
authors.forename: A
authors.initials: A
authors.lastname: Honohan
authors.forename: H
authors.initials: H
authors.lastname: Olthuis
authors.forename: A T
authors.initials: AT
authors.lastname: Bernards
authors.forename: J M
authors.initials: JM
authors.lastname: van Beckhoven
authors.forename: A
authors.initials: A
authors.lastname: Brand
mesh_terms: D001419:Bacteria / Q000166:cytology / Q000254:growth & development / Q000472:pathogenicity; D001793:Blood Preservation / Q000592:standards*; D002470:Cell Survival; D002498:Centrifugation; D015925:Cryopreservation / Q000592:standards; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D005312:Fetal Blood / Q000382:microbiology*; D006412:Hematopoietic Stem Cells / Q000382:microbiology*; D006801:Humans; D006895:Hydroxyethyl Starch Derivatives / Q000494:pharmacology
chemical_list: D006895:Hydroxyethyl Starch Derivatives; D004121:Dimethyl Sulfoxide