TRANSFUSION COMPLICATIONS Assessment of biofilm-forming ability of coagulase-negative staphylococci isolated from contaminated platelet preparations in Canada Carey Greco, Cherie Mastronardi, Franco Pagotto, Dietrich Mack, and Sandra Ramirez-Arcos 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 epi- dermidis, 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. epider- midis isolated from contaminated PLT preparations in Canada were distinguished via gene-specific poly- merase 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. Produc- tion 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 produc- ers. Three of the four biofilm-positive strains (75%) pro- duced 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. epi- dermidis 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. O f all blood products, platelet (PLT) prepara- tions are the most susceptible to bacterial contamination. 1 This finding can be attrib- uted to numerous PLT storage factors that contribute to the creation of a hospitable environment for aerobic microbial growth. PLT preparations are stored with constant agitation at room temperature for up to 5 days in bags designed to be oxygen permeable for optimal aeration. The PLT preparation itself is character- ized by an ideal physiologic pH and high glucose content (approx. 500 mg/dL) provided in part by an anticoagulant solution containing dextrose. Consequently, bacterial contamination of PLTs constitutes the highest posttrans- fusion infectious risk. 1 It has been documented that the most frequently identified bacterial contaminants of PLT preparations are coagulase-negative staphylococci (CoNS), and of these, ABBREVIATIONS: ATCC = American Type Culture Collection; ATR(s) = adverse transfusion reaction(s); CoNS = coagulase- negative staphylococci; PIA = polysaccharide intercellular adhesin; TSB(g) = trypticase soy broth (+0.5% glucose). From the Canadian Blood Services, Ottawa; the Microbiology Research Division, Bureau of Microbial Hazards, Food Director- ate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada; and Medical Microbiology & Infectious Dis- eases, Institute of Life Science, The School of Medicine, Swansea University, Singleton Park, Swansea, UK. Address reprint requests to: Sandra M. Ramírez-Arcos, MSc, PhD, Canadian Blood Services, 1800 Alta Vista Drive, Ottawa, Ontario, Canada K1G 4J5; e-mail: sandra.ramirez@blood.ca. This work was funded by a Canadian Blood Services Research & Development Intramural Grant awarded to Dr. S. Ramirez-Arcos. Ms. C. Greco holds a Canadian Blood Services Graduate Fellowship Program Scholarship. Received for publication September 27, 2007; revision received November 8, 2007, and accepted November 10, 2007. doi: 10.1111/j.1537-2995.2007.01631.x TRANSFUSION 2008;48:969-977. Volume 48, May 2008 TRANSFUSION 969