Abstract
Rapid identification of pathogens responsible for bloodstream infection is critical for early intervention and effective treatment. Reporter phages, which are known for their exceptional sensitivity and specificity in pathogen detection, have garnered significant interest. In this study, we systematically evaluate phage genome editing strategies that combine homologous recombination with the CRISPR-Cas9 system. We investigate the impacts of homologous arm length, sgRNA activity, target site, and plasmid interactions on editing efficiency. Our results demonstrate that successful genome editing depends on both sufficient cleavage pressure and optimal homologous arm length, particularly when using low-activity sgRNAs. On the basis of these findings, we develop a highly efficient gene editing strategy TPMSR (triple-plasmid-mediated synchronous recombination) that overcomes the limitations of conventional methods that rely on high-activity sgRNA and restricted editing sites. Using the TPMSR strategy, we integrate the Nluc gene into phage T7, generating the reporter phage T7:: Nluc, which is then incorporated into a microfluidic chip. Validation with 51 clinical isolates demonstrates outstanding sensitivity, specificity, and accuracy in detecting E. coli in blood within 1.5 h at concentrations less than 30 CFU/mL. This study presents a robust strategy for phage genome engineering and develops a promising method for the rapid diagnosis of bloodstream infections caused by Escherichia coli.