Some characteristics of platelet concentrates contaminated with Staphylococcus epidermidis

The study investigates platelet concentrates (PCs) contaminated with Staphylococcus epidermidis. The work was conducted using 12 pairs of PCs. Light transmission through the PCs was observed over 7 days. Immediately after preparation, one PC was inoculated with Staphylococcus epidermidis (17-43 colony forming units (CFU)/ ml) and the other served as a non-contaminated control. In the contaminated PCs the CFU/ml and swirling were determined on days 1, 3 and 7. In all PCs determination of pH and the extent of shape change (ESC) was carried out on days 3 and 7. All contaminated PCs had visible swirling on day 3 but they contained 2.0 X 10 4 to 9.0 X 10 8 CFU/ml. pH (P=0.05) and ESC (P<0.05) then were slightly lower. On day 7, eight of 12 of the contaminated PCs failed to display transmission changes despite deranged analytical results and impaired swirling. During early storage the contaminated units had unimpaired swirling and only slightly impaired in vitro quality. They appear to be difficult to identify in the routine.