Growth and Biofilm Formation of Bacteria Isolated from Contaminated Platelet Units

Abstract

Bacterial contamination of platelet concentrates (PCs) poses the major transfusion-associated infectious risk. Coagulase negative staphylococci (CoNS), the predominant platelet contaminants, are recognized as one of the leading causes of hospital-acquired infections due to their ability to form biofilms (surface-attached aggregates). In this study, 29 CoNS strains were characterized for their growth and biofilm formation abilities in media and PCs. Twenty-five strains were aerobic including Staphylococcus epidermidis, S. capitis, and S. chromogenes, while four were identified as the anaerobe S. saccharolyticus. Biofilm-associated icaA and icaD genes were amplified from eight strains. Interestingly, only six of those strains were biofilm-positive. Sequencing of S. capitis icaD revealed no mutations that could explain differences in biofilm phenotypes. Growth of CoNS in PCs varied significantly between strains. This study provides preliminary evidence that slow-growing biofilm-positive S. epidermidis are more likely to be missed during platelet culture, highlighting the need for improved screening methods.