| ironjustice@aol.com 2005-06-08, 11:51 am |
| Transfusion. 2005 Jun;45(6):927-33. Related Articles, Links
Non-transferrin-bound iron in platelet concentrates promotes the growth
of Staphylococcus epidermidis.
Matinaho S, Parkkinen J.
>From the Finnish Red Cross Blood Service, Helsinki, Finland.
BACKGROUND: Staphylococcus epidermidis, the most common organism
implicated in bacterial contamination of platelet (PLT) concentrates
(PCs), does not grow in serum unless transferrin is fully saturated and
there is non-transferrin-bound iron (NTBI) available. Here, the
occurrence and origin of NTBI in PCs has been studied. STUDY DESIGN AND
METHODS: NTBI in PC supernatants was determined by a chelation method
and by the bleomycin-detectable iron assay. Iron binding by transferrin
was determined by spectrophotometry, and transferrin iron forms, by
urea gel electrophoresis. The growth of inoculated S. epidermidis in PC
supernatants was monitored by optical density and determination of
viable counts. RESULTS: PCs contained approximately 0.14 micromol per L
redox-active iron measured by the bleomycin assay and approximately 0.7
micromol per L NTBI by the chelation method. As a further indication of
the presence of NTBI, the growth of S. epidermidis in the PC
supernatants was inhibited by iron chelation with deferoxamine.
Transferrin in the PC medium was only partially saturated with iron,
and the reason for the presence of NTBI was found to be impaired iron
binding by transferrin. Iron was displaced from transferrin by citrate
at molar ratios to transferrin that occur in citrated plasma and in PLT
additive solution (AS). Citrated plasma supported the growth of S.
epidermidis whereas serum did not. CONCLUSIONS: PCs stored in plasma or
AS contain a low level of NTBI because of the displacement of iron from
plasma-derived transferrin by citrate. NTBI in the PC medium supports
the growth of S. epidermidis.
PMID: 15934991 [PubMed - in process]
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