title: Noninvasive pH monitoring for bacterial detection in platelet concentrates.
abstract: Bacterial contamination of platelet concentrates (PCs) remains the prevalent posttransfusion infectious risk. The pH SAFE system, a noninvasive method used to measure pH of PC for quality control, was evaluated herein as a rapid method to detect bacterial contamination in PCs.
  
  
  
  Pairs of ABO-D-matched apheresis and buffy coat PCs were pooled and split into two pH SAFE platelet bags. One of the bags served as the control unit, while the other was inoculated with one of nine clinically relevant bacteria (target concentration approx. 1 colony-forming units [CFUs]/mL). The pH of both PCs was measured over 7 days of storage at approximately 4-hour intervals during daytime. One-milliliter samples were taken at the testing points to determine bacterial concentration.
  
  
  
  PCs with pH values of less than 6.6 or with a pH change over time (ΔpH/Δtime) greater or equal than 0.046 pH units/hr are suspected of being contaminated. pH decreased significantly during storage in all bacterially inoculated PC at concentrations of more than 10(7) CFUs/mL (p < 0.0001). A significant decrease in pH (p < 0.0001) was noticed as early as 28 hours in units with Bacillus cereus and as late as 125 hours in units containing Staphylococcus epidermidis. Interestingly, PCs containing Gram-negative species showed a decline in pH followed by a rebound.
  
  
  
  The pH SAFE system allows for repeated, noninvasive pH screening during PC storage. A significant decrease in pH could serve as an indicator of clinically significant levels of bacterial contamination. Since differences in pH decline were observed among bacterial species, continuous pH monitoring in PCs is recommended.
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Maria
authors.initials: M
authors.lastname: Loza-Correa
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Heather
authors.initials: H
authors.lastname: Perkins
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Dilini
authors.initials: D
authors.lastname: Kumaran
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Yuntong
authors.initials: Y
authors.lastname: Kou
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Ramie
authors.initials: R
authors.lastname: Qaisar
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Steven
authors.initials: S
authors.lastname: Geelhood
authors.affiliation: Canadian Blood Services, Ottawa, Ontario, Canada.
authors.forename: Sandra
authors.initials: S
authors.lastname: Ramirez-Arcos
mesh_terms: D001409:Bacillus cereus / Q000302:isolation & purification; D001424:Bacterial Infections / Q000517:prevention & control / Q000635:transmission*; D001792:Blood Platelets / Q000382:microbiology*; D001793:Blood Preservation; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017713:Platelet Transfusion / Q000009:adverse effects*; D011786:Quality Control; D013212:Staphylococcus epidermidis / Q000302:isolation & purification; D013997:Time Factors