NOVEL AUTOMATED MICROBIAL SCREENING OF PLATELET CONCENTRATES

The recovery of bacteria and the speed of detection of microbial growt h in platelet concentrates (PC) were studied, comparing a novel automa ted blood culture system (BacT/Alert) with two traditional methods. Fu ll-scale experiments were performed with a total of 33 units of PC (av erage content 320 x 10(9) platelets per unit) obtained from pooled buf fy coats. Six strains known as possible PC contaminants were tested: S . epidermidis, S. aureus, P. aeruginosa, B. cereus, E. aerogenes, and S. sanguis. Using an inoculum of 50-98 bacteria/ml, bacterial contamin ation was detected in all of 11 PCs on 132 sampling occasions. With a small inoculum (0.3-9 bacteria/ml), the bacterial contamination was de tected in all PCs in which abundant growth appeared, but failed to be detected in some instances where the bacterial content was very small. All of 11 uninoculated PC controls were negative. With the automated method the time for detection of a culture-positive PC was 6-16 h, cle arly shorter than with the two manual-visual systems. The new system p rovides a rapid, reliable, and labour-saving method for screening of b acterial contamination in PCs. This would increase safety particularly if the present 5-day shelf life were extended.