Enlargement of the WHO international repository for platelet transfusion-relevant bacteria reference strains

Background and ObjectivesInterventions to prevent and detect bacterial contamination of platelet concentrates (PCs) have reduced, but not eliminated the sepsis risk. Standardized bacterial strains are needed to validate detection and pathogen reduction technologies in PCs. Following the establishment of the First International Reference Repository of Platelet Transfusion-Relevant Bacterial Reference Strains (the repository'), the World Health Organization (WHO) Expert Committee on Biological Standardisation (ECBS) endorsed further repository expansion. Materials and MethodsSixteen bacterial strains, including the four repository strains, were distributed from the Paul-Ehrlich-Institut (PEI) to 14 laboratories in 10 countries for enumeration, identification and growth measurement on days 2, 4 and 7 after low spiking levels [10-25 colony-forming units (CFU)/PC bag]. Spore-forming (Bacillus cereusPEI-B-P-07-S, Bacillus thuringiensisPEI-B-P-57-S), Gram-negative (Enterobacter cloacaePEI-B-P-43, Morganella morganiiPEI-B-P-74, PEI-B-P-91, Proteus mirabilisPEI-B-P-55, Pseudomonas fluorescensPEI-B-P-77, Salmonella choleraesuisPEI-B-P-78, Serratia marcescensPEI-B-P-56) and Gram-positive (Staphylococcus aureusPEI-B-P-63, Streptococcus dysgalactiaePEI-B-P-71, Streptococcus bovisPEI-B-P-61) strains were evaluated. ResultsBacterial viability was conserved after transport to the participating laboratories with one exception (M.morganiiPEI-B-P-74). All other strains showed moderate-to-excellent growth. Bacillus cereus, B.thuringiensis, E.coli, K.pneumoniae, P.fluorescens, S.marcescens, S.aureus and S.dysgalactiae grew to >10(6) CFU/ml by day 2. Enterobacter cloacae, P.mirabilis, S.epidermidis, S.bovis and S.pyogenes achieved >10(6) CFU/ml at day 4. Growth of S.choleraesuis was lower and highly variable. ConclusionThe WHO ECBS approved all bacterial strains (except M.morganiiPEI-B-P-74 and S.choleraesuisPEI-B-P-78) for repository enlargement. The strains were stable, suitable for sp