Rab GTPases have been implicated in intracellular vesicle trafficking. Using the yeast two-hybrid screen, we have isolated a rat clone that interacts with Rab3A as well as with Rab1. The gene encodes a 20.6-kDa protein with two extensive hydrophobic domains and is broadly expressed in all tissues. This protein binds to prenylated Rab GTPases but not to other small Ras-like GTPases such as the Rho/Rac family. This prenylated Rab acceptor (PRA1) also binds specifically to the synaptic vesicle protein VAMP2 (or synaptobrevin II) but shows no affinity for VAMP1 or cellubrevin in both the yeast twohybrid system and in vitro binding assays. This specificity resides, in part, in the proline-rich domain of VAMP2 as a chimera containing this domain of VAMP2 fused to VAMP1 is able to bind to PRA1. The transmembrane domain of VAMP2 is also essential as its deletion abolished binding to PRA1. Replacement of the deleted VAMP2 transmembrane domain by a CAAX prenylation signal can not restore binding to PRA1. This interaction is therefore distinct from that required for VAMP2 binding to either syntaxin or both syntaxin and SNAP-25. Deletion analysis on PRA1 indicates that the critical Rab-and VAMP2-interacting residues reside in two regions: the amino-terminal residues 30 -54 and the extreme carboxyl-terminal domain. This dual Rab and VAMP2 binding characteristic suggests that PRA1 may serve to link these two protein families in the control of vesicle docking and fusion.

S. epidermidis forms biofilms on PLT aggregates and on PLT bags under PLT storage conditions. Our results demonstrate that the PLT storage environment can promote a BF growth mechanism for contaminant bacteria.

A 3-year-old girl with relapsed acute myelogenous leukemia received a transfusion of a 5-day-old single-donor volume-reduced HLA-matched platelet (PLT) unit before a CAT scan-guided drainage of pleural fluid. Within minutes of completing the transfusion, the patient, who was receiving a broad-spectrum antibiotic (meropenem), became febrile, confused, and hypotensive. Despite aggressive treatment, she died of multisystem organ failure 21 hours after transfusion. Blood and urine samples obtained from the recipient 18 hours after the transfusion, while on antibiotics, were negative for the presence of bacteria. Serratia marcescens, however, was isolated from cultures of the recipient's blood, urine, liver, and lung obtained at autopsy.Investigations were conducted at Canadian Blood Services, the PLT provider, and at the hospital. The PLT product was positive for the presence of Gram-negative bacilli, had 3.0 × 10 9 colony-forming units (CFUs) per mL of S. marcescens, and contained 194,400 EU per mL of endotoxin . Samples obtained from the plasma removed during volume reduction (performed 30 min before transfusion), the PLT filter, and saline solution attached to the PLT pack were positive for the presence of the same bacterium . Pulse-field gel electrophoresis genotyping of S. marcescens isolates from different samples showed that they had identical band patterns (Fig. 1).Several items having the same lot numbers as the items used during collection of the transfused unit, namely, plateletpheresis collection sets, vacutainer tubes, recalled and in-date apheresis PLT units, and secondary sample bags, were cultured and found to be negative for the presence of S. marcescens. Blood and urine samples provided by the donor were also negative for the presence of this bacterium, and the donor confirmed that he was not ill before or after the transfusion.Twenty-nine hours after collection, approximately 15 mL of PLTs from the implicated unit were transferred to a sample bag. This secondary bag was separated from the remaining PLTs, which were stored in a shaking incubator until they were volume-reduced and transfused. A sample of 4 mL of PLTs was taken from the sample bag and inoculated into an aerobic culture medium bottle (BPA) for testing of bacterial contamination with an automated blood culture system (BacT/ALERT, bioMérieux Canada Inc., St. Laurent, Québec, Canada). The culture was nega-Fig. 1. Genotyping of S. marcescens isolates. Genomic DNA was extracted from all of the bacterial isolates, followed by digestion with Spe I and pulse-field gel electrophoresis analysis at the Hospital for Sick Children, Toronto. Lanes M = = = = lambda ladder. Lanes 1 through 7 = = = = samples obtained during the investigation of this case: Lane 1 = = = = saline solution attached to the PLT pack; Lane 2 = = = = removed supernatant plasma; Lane 3 = = = = transfused PLT product; Lane 4 = = = = blood from the patient's central line; Lane 5 = = = = autopsy blood; Lane 6 = = = = autopsy liver; and Lane 7 = = = = autopsy left lung; Lanes 8 and...

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.

Alsever's solution has been used for decades as a preservative solution for storage of RBCs. From October 2005 to January 2006, unexplained hemagglutination of approximately 10 to 20 percent of RBCs stored for several days in a modified version of Alsever's solution was noticed in quality control testing at the Canadian Blood Services Serology Laboratory. An investigation, including microbial testing,was initiated to determine the cause of the unexplained hemagglutination. The gram-negative bacterium Serratia liquefaciens was isolated from supernatant solutions of agglutinated RBCs. Further characterization of this strain revealed that it has the ability to form biofilms; presents high levels of resistance to chloramphenicol, neomycin, and gentamicin; and causes mannose-sensitive hemagglutination. The source of S. liquefaciens contamination in RBC supernatants was not found. However, this bacterium has not been isolated since January 2006 after enhanced cleaning practices were implemented in the serology laboratory where the RBCs are stored. This biofilm-forming, antibiotic-resistant S.liquefaciens strain could be directly linked to the unexplained hemagglutination observed in stored RBCs. Immunohematology 2008;24:39-44.