title: pH value promotes growth of Staphylococcus epidermidis in platelet concentrates.
abstract: BACKGROUND
  The platelet (PLT) storage lesion is characterized metabolically by a pH value associated with lactic acid generation. PLT storage conditions support the growth of Staphylococcus epidermidis, the most common organism implicated in bacterial contamination of PLT concentrates (PCs). Here, different factors that influence bacterial growth in PCs are discussed and the relation between pH values of PCs and citrate plasma (CP) is studied, with emphasis on bacterial proliferation.
  
  
  METHODS
  The PLT lesion with regard to pH decrease and lactic acid production was monitored during storage and correlated to bacterial proliferation properties. A total of 115 coagulase-negative staphylococci, especially S. epidermidis isolates, were characterized for their proliferation in different blood components (CP, buffy coat-derived, and apheresis PCs). Furthermore, the influence of donor-specific, product-specific, species-specific, and strain-specific factors on bacterial proliferation was investigated.
  
  
  RESULTS
  PCs showed a lower pH value in comparison to plasma during storage. Bacterial proliferation in PCs and the failure to grow in CP were determined with all organisms tested. No correlation to donor-specific, species-specific, or strain-specific factors was observed. Lowering the pH of CP resulted in bacterial proliferation, whereas a pH increase in the PC unit inhibited the proliferation of S. epidermidis.
  
  
  CONCLUSIONS
  With emphasis on bacterial proliferation, the significant difference between PC and CP is the presence of metabolizing PLTs. The pH values of stored PLTs, but not those of stored plasma, support the growth of S. epidermidis.
authors.affiliation: Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabeteszentrum Nordrhein-Westfalen, Universitätsklinik der Ruhr-Universität Bochum, Bad Oeynhausen, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Störmer
authors.forename: Knut
authors.initials: K
authors.lastname: Kleesiek
authors.forename: Jens
authors.initials: J
authors.lastname: Dreier
mesh_terms: D016470:Bacteremia / Q000097:blood / Q000382:microbiology; D001782:Blood Donors; D001792:Blood Platelets / Q000378:metabolism / Q000382:microbiology*; D001793:Blood Preservation; D002951:Citrates / Q000097:blood; D015925:Cryopreservation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000097:blood*; D017713:Platelet Transfusion; D053657:Platelet-Rich Plasma / Q000378:metabolism / Q000382:microbiology; D013045:Species Specificity; D013203:Staphylococcal Infections / Q000097:blood* / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000254:growth & development* / Q000472:pathogenicity; D014774:Virulence
chemical_list: D002951:Citrates; D019344:Lactic Acid