Ghost-Particle-Enhanced Photoacoustic Flow Cytometry for Identification of Bacterial Cells in Body Fluids

Photoacoustic flow cytometry can detect small particles in flow by generating high-frequency ultrasonic waves in these particles given that there is optical contrast between the particles and the medium of flow. These ultrasonic waves indicate the presence of the particles and enable capture and further analysis. In the case of in vitro bacterial detection in body fluids for rapid identification of infection, we provide optical contrast using dyed bacteriophage that specifically targets bacterial cells. While these dyed and, hence, optically absorbing bacteriophages provide the optical contrast to bacteria for photoacoustic detection, the nature of bacteriophage results in lysis of the bacteria in an hour or so, thus precluding imaging or other analysis. In order to prevent lysis of the bacteria, but preserve the highly specific nature of bacteriophage to target bacterial species, we remove the capsids and the genetic material responsible for bacterial lysis and replace them with dyed latex microspheres. These engineered bacteriophage particles can therefore act as photoacoustic tags enabling detection and identification of bacterial species in body fluids while preserving the cells for imaging or molecular analysis.