Rate of growth of Pseudomonas fluorescens in donated blood

Abstract

Aims-To examine how delayed refrigeration of blood affects the growth of Pseudomonas fluorescens, one of the two most important causes of sepsis resulting from transfusion of contaminated blood. Methods-Two donations of whole blood were each divided into three aliquots and inoculated with 5-10 cfu/ml of a Pfluorescens strain from a case of transfusion associated sepsis. From each donation, one aliquot was placed at 4°C, one was held at 20°C for six hours prior to refrigeration and the third was held at 20°C for 24 hours prior to refrigeration. Samples were aseptically withdrawn over 17 days and bacterial counts were determined using a pour plate technique. Results-The rate of growth of Pfluorescens in blood at 20°C was increased compared with blood at 4°C. At 24 hours the aliquots held at 20°C for six and 24 hours had, respectively, 174 and 29 000 cfu/ml compared with 15 cfu/ml in aliquots held at 4°C. There was no evidence ofincreased killing of Pfluorescens at the higher temperature. Conclusions-These results suggest that blood for transfusion should be refrigerated as soon as possible after collection.