PLATELET BACTERIAL-CONTAMINATION AND THE USE OF A CHEMILUMINESCENCE-LINKED UNIVERSAL BACTERIAL RIBOSOMAL-RNA GENE PROBE

Background: Currently, the maximum outdate for platelets is 5 days, be cause of the increasing chance of bacterial growth over time; Various methods for rapid detection of bacterial contamination of blood compon ents have been described, with mixed results and no general acceptance . A recently described, molecular biologic approach for the detection of bacterial contamination involves a chemiluminescence-linked univers al DNA bacterial probe to a highly conserved bacterial region of ribos omal RNA (rRNA). Study Design and Methods: A multicenter trial of a ch emiluminescence-linked universal bacterial rRNA probe for the detectio n of bacterial contamination in platelet concentrates is described. At each of five sites, platelet concentrates (no older than 1 day from d ate of phlebotomy) were inoculated in triplicate with isolates of four bacterial species (Pseudomonas aeruginosa, Bacillus cereus, Staphyloc occus epidermidis, and Staphylococcus aureus) to a final concentration of 10 to 50 colony-forming units (CFUs) per mt and in triplicate to a final concentration of 1000 CFUs per mt. At one site, an additional 6 platelet concentrates were inoculated with sterile saline to serve as controls. Inoculated units were then subjected periodically to quanti tative cultures and probe analyses. A total of 126 platelet concentrat es were studied over a period of 7 days (120 inoculated with bacteria and 6 with sterile saline). Results: This assay was, in some cases, ab le to detect S. aureus bacterial contamination in the range of 100 to 1000 CFUs per mt; the majority of samples (B. cereus, Fl aeruginosa, S . aureus, and S. epidermidis) with contamination exceeding 10(4) CFUs per mt; and all samples with contamination of 2.1 x 10(5) CFUs per mt or greater. Increasing the sample size from the recommended 0.4 mt to 1.0 mt resulted in an unacceptable loss of specificity (83.3%). Conclu sion:The routine use of this assay would be expected to result in a de creased risk of septic platelet transfusion reactions and could lead t o a lengthening of the current 5 day storage period for platelets. Fur ther, the pooling of random-donor platelet concentrates before storage instead of immediately before transfusion may be possible if this rRN A probe is employed to detect bacteria in the pool.