Sterility testing of platelet concentrates prepared from deliberately infected blood donations.
BACKGROUND
In general the bacterial count in freshly donated blood is low and even lower in the corresponding platelet concentrates (PCs). By use of flow cytometry (FACS) for sterility testing, the reliability of early versus later sampling times was evaluated.


METHODS
Blood donations were spiked with various numbers of Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, and Klebsiella pneumoniae. The corresponding PCs were prepared by the buffy-coat method and stored at 22 degrees C. A 20-mL sample was collected from each PC directly after preparation and after 8 hours. Samples were stored at 35 degrees C. Sterility testing of both PCs and samples was by FACS analysis at different time points.


RESULTS
All stored PCs were found positive by FACS analysis, with detection times ranging between 8 and 24 hours (K. pneumoniae, B. cereus), 8 and 91 hours (S. aureus), and 144 hours (S. epidermidis). In the samples incubated at 35 degrees C, bacteria were detected after 8 to 19 hours (K. pneumoniae, B. cereus), 8 to 67 hours (S. aureus), and 19 to 43 hours (S. epidermidis). Some of the samples did not contain bacteria.


CONCLUSIONS
Detection times for slow-growing bacteria are significantly shortened when PC samples are incubated at 35 degrees C: the numbers of bacteria in freshly prepared PCs may, however, be so low that the samples drawn for sterility testing do not contain a single bacterium. Our results do not support a shortening of the 24-hour or greater sampling time recommended by the manufacturers of established test systems, because also for consistent detection by FACS, bacteria need to grow in the PCs to sufficient numbers.
Blood Center of the German Red Cross Chapters of NSTOB, Institutes Springe and Gera, Springe and Gera, Germany. hmohr@bsd-nstob.de
Harald
H
Mohr
Bernd
B
Lambrecht
Anette
A
Bayer
Hans-Peter
HP
Spengler
Sven-Boris
SB
Nicol
Thomas
T
Montag
Thomas H
TH
Müller
D001419:Bacteria / Q000166:cytology* / Q000254:growth & development; D001424:Bacterial Infections; D001431:Bacteriological Techniques; D001782:Blood Donors; D001792:Blood Platelets / Q000166:cytology* / Q000382:microbiology; D001793:Blood Preservation / Q000379:methods; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D006358:Hot Temperature; D006801:Humans; D017053:Infection Control / Q000379:methods; D008297:Male; D012680:Sensitivity and Specificity; D013997:Time Factors