Detection of bacteria in stored red cell products using a culture-based bacterial detection system

The Pall eBDS uses oxygen consumption as a surrogate marker for bacterial detection in platelet (PLT) products. This article describes the evaluation of eBDS to detect bacterial contamination in inoculated fresh and stored leukoreduced red cell (RBC) units.

Field studies were conducted at three sites to establish eBDS pouch incubation time and the pass/fail threshold. RBC units were inoculated with each of 12 bacterial species known to cause sepsis at target inocula of either 1 to 15 or 100 colony-forming units (CFUs) per mL. Units were mixed and stored at 2 to 6 degrees C. Samples were taken for culture and eBDS testing weekly from 0 hour to 42 days and incubated for 35 degrees C for 24 to 30, 48, and 72 hours, followed by measurement of percent oxygen content.

The studies showed growth of five bacterial species (including Yersinia enterocolitica) in RBC units, while seven bacterial species showed no growth or autosterilized. A pass/fail oxygen threshold of 14.4 percent was determined based on results from noninoculated controls (n = 633) and from inoculated samples (n = 884) after 48 hours of incubation. Detection was 100 percent at all sampling times during refrigerated storage with both 48 and 72 hours of pouch incubation.

With incubation of eBDS pouches for 48 and 72 hours, 100 percent detection was obtained in 884 samples with bacterial levels of at least 1 CFU per mL, and no false-positive samples were obtained. Based on the bacterial growth patterns, RBC units may be sampled 1 to 3 days after collection for optimal efficacy and read after 48 to 72 hours of incubation of the eBDS sample pouches at 35 degrees C. The Pall eBDS is suited for detection of typical bacterial contaminants in fresh and stored RBCs.