title: Estimation of bacterial risk in extending the shelf life of PLT concentrates from 5 to 7 days.
abstract: BACKGROUND
  The use of bacterial culture to prevent bacterial contamination of blood components has renewed interest for extending the shelf life of PLT concentrates to 7 days after collection.
  
  
  METHODS
  This study was therefore conducted to determine the residual risk of bacterial contamination in PLT concentrates at the end of 5 and 7 days after collection in a center where all PLT concentrates are routinely screened by taking samples on Day 2 for culture. PLT units with no growth after 48 hours were sampled a second time on Day 5 or Day 7 after collection, followed by inoculation into aerobic culture bottles. The inoculated bottles were then monitored for up to 7 days at 35 degrees C in an automatic monitoring and detection system.
  
  
  RESULTS
  During a 16-month study period, a total of 6020 PLT concentrates were tested 5 days (Group A, n=3010) and 7 days (Group B, n=3010) after collection. Four units in each group (0.133%) were found to be contaminated. In 6 units, bacteria were seen on direct Gram stain. In addition, 5 of the associated RBC units grew the same organisms on culture. The organisms include three coagulase-negative staphylococci and five Propionibacterium acnes. The positive rate of routine short-term bacterial culture was 0.035 percent during the same study period.
  
  
  CONCLUSIONS
  Despite routine short-term bacterial culture, a significant risk of bacterial contamination remains at 5 and 7 days after collection. For now, the shelf life of PLT concentrates should remain 5 days.
authors.affiliation: Hong Kong Red Cross Blood Transfusion Service and Center of Infection and Department of Microbiology, the University of Hong Kong, Hong Kong. ckleea@ha.org.hk
authors.forename: C K
authors.initials: CK
authors.lastname: Lee
authors.forename: P L
authors.initials: PL
authors.lastname: Ho
authors.forename: K Y
authors.initials: KY
authors.lastname: Lee
authors.forename: W W
authors.initials: WW
authors.lastname: Cheng
authors.forename: N K
authors.initials: NK
authors.lastname: Chan
authors.forename: W C
authors.initials: WC
authors.lastname: Tsoi
authors.forename: C K
authors.initials: CK
authors.lastname: Lin
mesh_terms: D001419:Bacteria / Q000254:growth & development*; D001769:Blood / Q000382:microbiology*; D001792:Blood Platelets / Q000382:microbiology*; D001793:Blood Preservation; D015169:Colony Count, Microbial; D006801:Humans; D012307:Risk Factors; D013997:Time Factors