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Background: Canadian Blood Services performs bacterial screening of buffy coat platelet pools (BCPs) using aerobic BacT/ALERT cultures. This study aimed to determine the rate of detection failures during initial platelet (PLT) screening and evaluate the introduction of anaerobic cultures and immunoassay testing to assess the safety of extending PLT storage beyond 5 days., Study Design and Methods: Outdated (7- to 10-day-old) BCPs that tested negative during initial screening were assayed with BacT/ALERT and the Verax PLT Pan Genera detection (PGD) test, an immunoassay that detects Gram-positive (GP) and Gram-negative (GN) bacteria. BacT/ALERT aerobic and anaerobic culture bottles were inoculated with 8 to 10 mL of BCP and incubated for up to 6 days. The PGD test was performed following manufacturer's instructions. Positive results were confirmed using the BacT/ALERT and PGD tests, blood agar culture, and Gram staining. Invalid PGD results were investigated., Results: A total of 4002 BCPs were tested with one (0.025%) true positive (Staphylococcus epidermidis) found by both the BacT/ALERT and the PGD assays. Fifty-four (1.35%) false-positive BacT/ALERT cultures were obtained mainly due to instrument errors involving anaerobic cultures. Eleven (0.27%) false-positive PGD tests were observed in the GP window of the strip. Forty-nine (1.2%) invalid PGD results were obtained mostly before implementation of a humidity chamber., Conclusion: Testing of outdated BCPs suggests that introducing anaerobic cultures would result in significant PLT wastage due to a high rate of false positives. Contaminated BCPs still escape detection during initial testing; therefore, extension of PLT storage may be possible if repeat screening is performed before transfusion., (© 2011 American Association of Blood Banks.)

Background: Coagulase-negative staphylococci (CoNS) are the most prevalent bacterial contaminants of platelet (PLT) preparations and have been implicated in adverse transfusion reactions worldwide. The most frequently identified contaminant is Staphylococcus epidermidis, which is noted for its ability to maintain chronic hospital-acquired infections by forming biofilms as a chief virulence mechanism., Study Design and Methods: Strains of S. epidermidis isolated from contaminated PLT preparations in Canada were distinguished via gene-specific polymerase chain reaction (PCR) with divIVA as a marker. Biofilm-forming ability was assessed by the presence of the gene icaD, slime production on Congo red agar, and biofilm formation on polystyrene surfaces. Production of polysaccharide intercellular adhesin (PIA) was resolved by immunofluorescence., Results: Eight of the 13 (62%) CoNS isolates under study were identified as S. epidermidis. Of these, four strains (50%) were classified as strong biofilm producers. Three of the four biofilm-positive strains (75%) produced slime, harbored the icaD gene, and had positive expression of PIA., Conclusions: Despite the presumable commensal origin of the CoNS isolates, a large proportion of S. epidermidis strains demonstrated a potential for enhanced virulence. Identification of contaminant staphylococci as biofilm producers is thus relevant and informative with regard to treatment approach in the circumstance of inadvertent infection of a PLT recipient.

Background and Objectives: Bacterial screening in apheresis platelet preparations was implemented in March of 2004 by Canadian Blood Services (CBS) using the BacT/ALERT system. The aim of this study was to develop, validate and implement an in-house proficiency testing programme to evaluate CBS performance of bacterial screening in platelet preparations., Study Design and Methods: During development of the proficiency testing programme, apheresis platelet preparations were spiked with 10(1) and 10(2) colony forming units per ml of Staphylococcus epidermidis, Pseudomonas aeruginosa and Streptococcus pneumoniae. The preparations were stored at 2-8 degrees C prior to culture bottle inoculation with 4 or 6 ml on Days 7-10 (estimated time from panel preparation to testing at CBS centres). Upon implementation, a combination of four proficiency panel members, including positives and negatives, were distributed to each of the centres that participated in the programme. A survey was conducted with 43 America's Blood Centers to assess whether they screen for bacterial testing in platelet preparations and whether they have implemented a proficiency testing programme., Results: The development of the proficiency testing programme showed that S. epidermidis and P. aeruginosa produced positive results at both concentrations and volumes on Days 7-10 poststorage. Streptococcus pneumoniae did not grow consistently and therefore was not selected for implementation of the programme. Two proficiency testing panel sets have been issued (July 2006 and February 2007) with 14 out of 15 (93%) and 14 out of 14 (100%) of the participant centres meeting the expected results for bacterial screening, respectively. The majority (72%) of the America's Blood Centers that screen for bacterial contamination have not implemented a proficiency testing programme and 94.4% of these centres are interested in developing such a programme., Conclusion: Canadian Blood Services has successfully implemented a proficiency testing programme for bacterial screening in platelet preparations, which will contribute to improving the safety of the platelet supply in Canada.