Rapid and high-sensitivity quantitative fluorescent immunoassay for detection of

Introduction: Early and precise identification of Methods: The assay employs a sandwich immunoassay format, which utilizes carboxylated magnetic agarose microspheres for capture and time-resolved fluorescent microspheres for detection. It enables quantification of the KPC protein within approximately 1 h. The analytical performance of the assay was systematically evaluated, including its sensitivity, linear range, specificity and accuracy. Results: Under optimal experimental conditions, it exhibits a wide linear range (0.25-1000 ng/mL) and a low detection limit of 0.194 ng/mL, and shows no cross-reactivity with other common carbapenemases. Recovery rates in bacterial lysates ranged from 96.7 to 108.4%. Compared to a commercial immunochromatographic test, this method demonstrated superior sensitivity. Discussion: The primary advantage of this fluorescent immunoassay is its ability to achieve rapid, sensitive and quantitative detection of KPC, which addresses a key limitation of current qualitative methods. Its wide linear range and low detection limit enable precise monitoring of KPC expression level variations, offering a novel tool for the clinical assessment of bacterial resistance burden.