Staphylococcus Aureus Detection In Platelets Using Short Synthetic Peptides Derived From Phage-Displayed Random Peptide Libraries Coupled with Quantum-Dot Nanocrystals

Bacterial sepsis in recipients of transfusion products due to contamination of blood components is an infrequent but serious and potentially a fatal complication. Unlike red cells, platelet concentrates (PC) are stored for up to 5 days at room temperature after collection, which is conducive for bacterial growth. In 42% of the sepsis cases following PCs, the most common bacterial contaminant is Staphylococcus spp. Timely detection of these contaminated units is a public health priority. Although a multitude of bacterial diagnostic tests are available for PCs, still there is a need for developing more sensitive, specific and rapid detection assays. The primary objective of this study is to develop a simple and highly sensitive procedure that facilitates rapid and enhanced detection of bacteria using Staphylococcus aureus as a model for PCs.

A commercially available bacteriophage-displayed random 12-mer peptide library was screened against S. aureus. The screening and subsequent sequencing of the phage DNA identified a phage clone containing a coding sequence for 12-amino acid peptide that selectively binds to S. aureus. We assessed the binding specificity and detection sensitivity of the peptide to a panel of six bacteria spiked in platelets (including S. aureus) by dot blot, ELISA and fluorometry. The peptides were further labeled with streptavidin-conjugated fluorescent Nanocrystal quantum-dots (Q-dots) to enhance the sensitivity of the assay.

The membrane-based dot blot method revealed that the peptide binds specifically to S. aureus. ELISA and fluorometry analysis of spiked platelet samples revealed that the peptide binds to S. aureus at 10³ CFU/ml concentrations. By using the peptide-Nanocrystal Q-dot combination (peptide probes), the detection sensitivity was further enhanced. The peptide binding remained relatively constant between pH 5 to 7.5.

This model system demonstrates that peptides derived from random phage library in combination with Nanocrystal Q-dots facilitate high sensitivity detection of S. aureus. In general, this study provides a proof-of-concept that ‘peptide probes' selected against specific bacteria are useful in detecting and monitoring them in various settings relevant to blood safety and transfusion medicine.

The findings and conclusions in this abstract have not been formally disseminated by the Food and Drug Administration and should not be construed to represent any Agency determination or policy.

No relevant conflicts of interest to declare.