Growth of Yersinia species in artificially contaminated blood bags.

Transfusion blood bags were inoculated with less than 0.1 colony-forming units (CFU) of Yersinia enterocolitica (serotypes O:3, O:5, and O:9) and Yersinia pseudotuberculosis I per mL and stored at 4 degrees C for 41 days. During storage, samples were collected periodically and colony counts of serial dilutions were performed by plating on tryptic soy agar. After a lag-phase, the growth of Yersinia species from less than 0.1 CFU per mL to 10(9) CFU per mL was observed in 3 of 10 bags. The data showed that prolonged storage of contaminated blood bags allows Y. enterocolitica and Y. pseudotuberculosis to multiply to high levels.