Inhibitory effect of 0°c storage on the proliferation of Yersinia enterocolitica in donated blood

BACKGROUND: Yersinia enterocolitica is frequently identified in cases of bacterial sepsis due to red cell transfusion. One of the features that makes Y: enterocolitica particularly dangerous is that, unlike most other bacterial contaminants of blood components, this organism can actively multiply in currently recommended refrigerator temperatures (1-6°C). The effect of a colder than normal storage temperature on Y. enterocolitica growth was investigated to determine whether bacteria growth could be reduced or inhibited at 0°C. STUDY DESIGN AND METHODS: Twenty-four units of freshly collected donated blood were obtained. Three sets of 7 units each were inoculated with Y. enterocolitica O:3, Y. enterocolitica O:20, and Y. enterocolitica O:5, 27, respectively. The remaining 3 units served as uninoculated controls. Each of the 24 bags was split into two equal aliquots, with one aliquot stored at 4°C and the other at 0°C. Bacteria growth was measured twice weekly for 6 weeks. Endotoxin and hemoglobin levels were also measured at selected intervals. RESULTS: Bacteria growth was detected earlier and in higher concentrations in the aliquots stored at 4°C. Twenty-two of the 42 inoculated aliquots had measurable bacteria growth. Thirteen aliquots had been maintained at 4°C, and nine had been stored at 0°C. Sixteen of these 22 aliquots were matched pairs. Exponential growth was detected after 14 to 32 days in the 4°C aliquots and after 28 to 39 days in the 0°C aliquots. Final bacteria counts were much higher in the 4°C aliquots (10⁵-10¹⁴ colony-forming units/mL) than in the 0°C aliquots (10¹-10⁴ colony-forming units/mL) on Day 42. Endotoxin was present in all 13 of the 4°C aliquots with actively growing Y. enterocolitica. CONCLUSION: Storage of red cells at 0°C markedly prolongs the time required for Y. enterocolitica to achieve exponential growth and results in lower concentrations of bacteria.