Presence of Propionibacterium acnes in blood components

BACKGROUND: Sterility testing, as part of the QC of blood components at the Japanese Red Cross Aichi Blood Center between April 1998 and March 2000, showed that 10 of 5568 tested blood components (0.18%), all of which were RBC concentrates, were contaminated with bacteria. Nine isolates were Propionibacterium acnes and one was Staphylococcus capitis. STUDY DESIGN AND METHODS: To investigate the molecular relatedness of eight available P. acnes isolates, 16S rRNA gene analysis and random amplified polymorphic DNA (RAPD) analysis were performed. RESULTS: DNA sequencing analysis of the 16S rRNA gene showed that five isolates were identified as distinct strains and that three had identical sequences. RAPID analysis in the latter three isolates showed that two exhibited indistinguishable banding patterns that differed from that of the third isolate. CONCLUSION: P acnes was the most frequent contaminant of blood components, and six of eight isolates were molecularly unrelated. Further studies are necessary to investigate the precise mechanisms of contamination.