Two-year experience with aerobic culturing of apheresis and whole blood-derived platelets.
BACKGROUND
Throughout its system of regional centers, Blood Systems implemented culture based bacterial testing with a standardized protocol for both apheresis and whole blood-derived platelets (PLTs).


METHODS
After a 24-hour hold, 4 mL of PLT product was inoculated into an aerobic bottle (BacT/ALERT, bioMérieux). Cultures were incubated for 24 hours before routine product release to prevent distribution of infected products while minimizing consignee notification, product retrievals, and hospital PLT inventory problems. Initial-positives were further tested (and bacteria identified) by performing cultures from the original component and subcultures from the BacT/ALERT bottle. Results were categorized according to AABB recommended definitions with minor modifications.


RESULTS
The rate of true-positive detections from culturing 122,971 apheresis PLTs was 0.017 percent (95% confidence interval [CI], 0.011%-0.026%). All true-positive microorganisms were Gram-positive with a predominance of coagulase-negative Staphylococcus and Bacillus species. Twenty of the 21 true-positive samples (95%) were detected by 24 hours but only 14 (68%) were detected by 18 hours. The false-positive rate due to contamination was 0.1 percent with the majority of isolates being skin or environmental organisms. Results did not differ significantly for whole blood-derived versus apheresis PLTs.


CONCLUSIONS
These data corroborate the fact that the rate of detection of truly contaminated PLT apheresis products in the United States is approximately 1 in 5000 (0.02%); this is lower than the 0.03 to 0.05 percent rates that were generally quoted in the literature before the implementation of prospective bacterial culturing programs.
Kleinman
Steven H
SH
Blood Systems Research Institute, San Francisco, California, USA.
Kamel
Hany T
HT
Harpool
Dennis R
DR
Vanderpool
Sandra K
SK
Custer
Brian
B
Wiltbank
Thomas B
TB
Nguyen
Kim-Anh
KA
Tomasulo
Peter A
PA
D001407:Bacillus / Q000254:growth & development*; D001771:Blood Banks; D001792:Blood Platelets / Q000382:microbiology*; D001793:Blood Preservation / Q000379:methods; D015169:Colony Count, Microbial / Q000379:methods; D005189:False Positive Reactions; D006801:Humans; D010983:Plateletpheresis / Q000379:methods; D011446:Prospective Studies; D011786:Quality Control; D015203:Reproducibility of Results; D013203:Staphylococcal Infections / Q000517:prevention & control; D013210:Staphylococcus / Q000254:growth & development*; D014481:United States