A Recyclable Affinity Chromatographic Device for Rapid Colorimetry of Bacteria Using Phage-Derived Cell Wall Binding...

Traditional methods for detecting bacteria are usually limited by low efficiency, high cost, and resource dependency. This study developed a recyclable affinity chromatographic device using phage-derived cell wall binding domains (CBDs) as recognition ligands for point-of-care testing of bacteria. The device trapped nickel-crosslinked resin (NR) beads within two layers of PTFE sieve, enabling efficient conjugation of His-tagged CBD. With a horseradish peroxidase (HRP)-based colorimetry, Acinetobacter baumannii (A. baumannii) was detected by using CBD18 and polymyxin B-HRP conjugate as the recognition ligand and signal tracer, respectively. With the same protocol, CBD108 and vancomycin-HRP conjugates were used for the colorimetry of methicillin-resistant Staphylococcus aureus (MRSA). In this process, the affinity chromatographic device was eluted using an imidazole solution, enabling its recycling use. With the device, A. baumannii and MRSA were quantified within 30 min, with linear ranges of 2.4 × 10²-2.4 × 10⁸ CFU/mL and 2.1 × 10²-2.1 × 10⁸ CFU/mL, respectively. It exhibited high selectivity for the target bacteria due to the combinational usage of CBDs and antibiotics. The NR beads trapped in the device maintained a conjugation performance of no less than 93.6% after 20 run cycles. This study provides a rapid, sensitive, and recyclable technical tool for point-of-care testing of bacteria in resource-limited countries and institutes.