Value of anaerobic culture in bacterial surveillance program for platelet concentrates

Short-term aerobic bacterial culture (STABC) has been used routinely in Hong Kong since 1998 to reduce bacterial contamination in platelet concentrates (PCs) with good results. With more countries implementing routine aerobic and anaerobic cultures of PCs, a prospective study was conducted to determine the value of anaerobic culture to STABC.

PC tested by STABC was used as control. Twenty milliliters of the PC selected for this study was aliquoted and pooled for 7 days aerobic and anaerobic culture. If the initial culture was positive, samples retrieved from the original PC and their associated components were cultured for confirmation and microbiologic identification.

A total of 10,035 PC units (2007 pools) were tested. The confirmed positive rates by aerobic and anaerobic cultures per pool were 3 (0.15%) and 13 (0.65%), respectively, which was equivalent to an increased yield from 0.03 to 0.13 percent of PC if anaerobic culture was added. Of the 10 bacteria detected by anaerobic culture only, 9 were found to be Propionibacterium acnes and the remaining one Peptostreptococcus sp. Their mean detection time from inoculation was 92.16 hours (range, 50.4-124.8 hr).

Addition of anaerobic culture to our routine STABC would significantly increase the detection rate of bacterial contaminated PC. However, since only slow-growing bacteria were detected, and because their clinical significance was uncertain, it is concluded that there was no clear justification to introduce anaerobic culture locally if 5-day shelf life for PCs was to be maintained.