Cationized magnetoferritin enables rapid labeling and concentration of Gram-positive and Gram-negative bacteria in magnetic cell separation columns

In order to identify pathogens rapidly and reliably, it is often required to capture and concentrate them from large sample volumes into smaller ones. Magnetic labeling and capture of bacteria using a magnetic field holds great promise towards achieving this goal, but current protocols suffer from poor capture efficiency. Here, we present a rapid and highly efficient approach to magnetic labeling and capture of both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria using cationized magnetoferritin (cat- MF). Magnetic labeling was achieved within a one minute incubation period with cat-MF, and 99.97% of the labeled bacteria could be immobilized in commercially available magnetic cell separation (MACS) columns. Longer incubation times led to more efficient capture, with S. aureus being immobilized to a greater extent than E. coli. Finally, low numbers of magnetically labeled E. coli (< 100 colony forming units per mL) were immobilized with 100% efficiency and concentrated 7-fold within 15 minutes. Therefore, our study provides a novel protocol for rapid and highly efficient magnetic labeling, capture and concentration of both Gram-positive and Gram-negative bacteria.