A PROSPECTIVE MICROBIOLOGIC SURVEILLANCE PROGRAM TO DETECT AND PREVENT THE TRANSFUSION OF BACTERIALLY CONTAMINATED PLATELETS

After two patients received bacterially contaminated platelet transfus ions, a prospective surveillance program was instituted to perform Gra m staining and microbiologic culturing of platelets at the time of tra nsfusion. In 12 months, 3141 random-donor platelet pools (prepared fro m 14,481 units) and 2476 single-donor apheresis units were cultured. A ll single-donor apheresis units were sterile, but 6 (0.19%) of the ran dom-donor pools were found to be bacterially contaminated, with 1 unit of 5 in the pool being the source in each case. Contaminants were Sta phylococcus epidermidis (4 cases), Bacillus cereus (1), and Staphyloco ccus aureus (1) at counts of 0.5 x 10(2) to 10(11) colony-forming unit s per mL in platelet pools and 10(3) to 10(13) colony-forming units pe r mt in source units. The contamination rate for units transfused at l ess than or equal to 14 days (1.8/10,000) was significantly lower than that at 5 days (11.9/10,000; p<0.05), as was the magnitude of contami nation (p<0.05). Use of the pretransfusion Gram stain on 4- and 5-day- old platelet pools was 100 percent sensitive (4/4 true positives) and 99.93 percent specific (1 false positive) In detecting contaminated po ols. These data define the extent and magnitude of platelet bacterial contamination and demonstrate the efficacy of the pretransfusion Gram stain on platelet units stored for 4 and 5 days in preventing the tran sfusion of heavily contaminated units. It is concluded that the risk o f platelet contamination is related to the duration of component stora ge. Transfusion services can minimize this risk by selecting shorter p latelet outdates or by screening 4- and 5-day-old platelets with a pre transfusion Gram stain.