Visual identification of bacterially contaminated red cells

Abstract

There have been increasing numbers of reports of transfusion-acquired Yersinia enterocolitica bacteremia (including several fatal cases). Fifteen units of whole blood were inoculated with various concentrations of Y. enterocolitica serotype 0:3 and processed into AS-3 preserved red cells (RBCs). Consistent growth of the organism was found at inoculum concentrations greater than or equal to 10 colony-forming units per mL. In all 13 units of RBCs that supported the growth of Y. enterocolitica, a darkening in color (due to hemolysis and a decrease in pO2) was observed in the bag. The attached sample segments, which were sealed from the main unit, remained sterile and did not darken. This color change was apparent in all the contaminated units by Day 35, which was 1.5 to 2 weeks after the bacteria were first detected in cultures of the blood. Hence, by comparison of the color of the segment tubing with that of the unit itself, units grossly contaminated with Y. enterocolitica can be identified prior to transfusion. Moreover, review of photographs on file at the Centers for Disease Control revealed this dramatic color change in 2 units of blood that caused transfusion-transmitted sepsis (Enterobacter agglomerans and an unidentified gram-negative bacillus, not Yersinia sp.), which demonstrated that the color change was not limited to Y. enterocolitica. This method of visual identification of contaminated units of blood could decrease the incidence of posttransfusion bacterial sepsis.

Transfusion-related bacterial sepsis

“…The color change during growth of psychrophilic bacteria first appears in units with titers exceeding 4 x 108 CFU/ml (147). Heavily contaminated erythrocytes that display this darkened appearance also have low oxygen tension (<5 torr [1 torr - 133 Pa]) compared with uncontaminated components (>50 torr) (76). Similar observations have been made by Wenz and colleagues (149).…”

“…The higher levels of methemoglobin measured in contaminated units (two-to fourfold over uncontaminated controls) may partially contribute to this color change as well (149). Color alterations have also been observed in heavily contaminated units containing Enterobacter agglomerans and an unidentified gram-negative bacillus (76). Other, more subtle changes may also appear.…”

“…Hemolysis in erythrocyte units with high levels of Y enterocolitica was found by Kim and colleagues to be five times that of uncontaminated, paired controls (78). In addition, Kim and coworkers noted that heavily contaminated erythrocyte units often appear much darker than normal (76). This darker color can be discerned by comparing the color of the container to that of attached tubing, which is sealed at the time of component preparation.…”

Current Concepts on Transmission of Bacteria and Parasites by Blood Components

“…Visual inspection -All units must undergo visual inspection before being released for transfusion, with special attention to the presence of clots (14) (the amount of citrate decreases due to its use in bacterial metabolism as a carbon source), hemolysis (15) (especially when it is present only in the blood bag and not in the attached segment), or a "pearlescent swirl" in platelet units (16). Inactivating agents -Antibiotics have been proposed as components of storage preservati ve medium; however, this measure is no longer used.…”

Transfusion-Associated Bacterial Sepsis

“…Unfortunately, this method's sensitivity is very low. It is possible to detect bacteria when their concentration is 10 5 -10 6 CFU/ml (59). When the two methods of detecting bacteria in blood were compared (culturing on bacteriological medium and microscopic assessment), more than half of the samples where bacteria were cultured were negative microscopically (60).…”