Factors affecting Yersinia enterocolitica (serotype O:8) viability in deliberately inoculated blood

Interpretation of in vitro experiments using Yersinia enterocolitica in blood components requires information on factors affecting the organism's survival. Several factors were found to influence the survival of Y. enterocolitica (serotype O:8) in blood components. A 20- minute room-temperature incubation with plasma-containing components resulted in approximately 2 log10 inactivation. Inactivation could be prevented by preincubation treatment of the plasma at 55 degrees C for 1 hour, which suggests the involvement of heat-labile plasma factors. No antibacterial activity was observed in washed red cells during the 20-minute room-temperature incubation. However, Y. enterocolitica colony-forming units declined by up to 2 log10 in washed red cells during the first days of 4 degrees C storage. Use of a white cell- reduction filter on freshly inoculated samples removed approximately 1 log10 of the organism regardless of whether bacteria were suspended in saline or washed red cells. Thus, bacterial levels may be affected by plasma, cellular components, and white cell-reduction filters. However, caution should be exercised in interpreting in vitro spiking studies designed to investigate the potential benefits of white cell reduction to eliminate the growth of Y. enterocolitica because of potential differences between naturally infected and experimentally inoculated blood.