Microbial contamination of the Tzu-Chi cord blood bank from 2005 to 2006

Background: In total, 4502 units of cord blood (CB) were collected during a 2-year period from 2005 to 2006 by the Buddhist Tzu-Chi Stem Cells Center. The aim of this study was to analyze the incidence of microbial contamination and type of organism present in the cord blood. The clinical impact of microbial contamination on hematopoietic progenitor cell (HPC) grafts used for HPC transplantation is also discussed. Methods: First and second specimens were obtained for microbial assessment. These were collected in laboratory after cord blood collection and after cord blood unit manipulation, respectively. The samples were cultured and the results reviewed. Results: The overall incidence of microbiological contamination was 1.8% (82/4502). Three CB units were contaminated with two different organisms. Infectious organisms comprised 9. 4%(8/85) of total isolated microbes. These infectious microorganisms were β-Streptococci group B, Candida tropicalis and Staphylococcus aureus which were isolated in 6, 1 and 1 of CB units respectively. Escherichia coli, Bacteroides fragilis, Lactobacillus spp., Enterococcus, β-Streptococcus Group B, Bacteroides valgatus, Corynebacterium spp., Klebsiella pneumonia and Peptococcus spp. were the most frequently encountered microorganisms. A higher contamination rate of the CB units was noted after vaginal delivery (2.16%) compared to caesarian section (0.85%) (p<0.01). Conclusions: Extensive training in CB collection, good procedures and good protocols can decrease the rate of microbial contamination. The use of a closed collecting system and an ex utero method have the advantage of a lower contamination rate. In our cord blood bank, we use a closed system but an in utero method. Similar to other studies, most of microorganisms reported here as contaminants are non-pathogenic.