The fate of bacteria in frozen red cells

Units of blood were intentionally contaiminated with suspensions of either Aerobacter aerogenes, Escherichia coli, Bacillus subtilis, Enterobacter cloacae, Pseudomonas aeruginosa, Sarcina lutea, Seratia marcesens, Staphylococcus epidermidis, Streptococcus faecalis, Paracolabacterum aerogenoides (Enterobacter hafriae), Mima polymorpha or Acinetobacter- calcoaceticus. When inoculation was made prior to glycerolization, the subsequent glycerolization, freezing, thawing, and deglycerolization resulted in roughly a two log reduction in the number of bacteria. When inoculation was made with a final concentration of between 10(1) and 10(5) organisms per milliliter, immediately following deglycerolization or following washing without glycerolization and freezing, no increase in the number of bacteria was seen after 72 hours storage at 4 C. Three of the 12 organisms studied decreased in number during 72 hours of storage. These data suggest that the current 24-hour limit on the post-thaw storage of frozen red blood cells may be unnecessarily restrictive.