A platform for specific and sensitive detection of target bacteria by selective magnetic enrichment and a broad-spectrum fluorescent probe

Abstract The indiscriminate application of antibiotics has led to the spread of antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella pneumoniae carbapenemase 2-expressing Klebsiella pneumoniae (KPC-2 KP), resulting in a global threat to public health. A method for specific, sensitive, and rapid detection of such bacteria is essential for clinical diagnosis and treatment. In this study, target bacteria were selectively captured using aptamer-coated magnetic beads (Apt-MBs), followed by recognition and detection by a broad-spectrum fluorescent probe, fragment crystallizable mannose binding lectin-coated gold nanoclusters (FcMBL@AuNCs). As a proof of concept study, a Gram-positive bacterium (i.e., MRSA) and Gram-negative bacterium (i.e., KPC-2 KP) were selected as models and detected by the proposed strategy. The determination of MRSA and KPC-2 KP was in the range of 20-108 CFU/mL with a detection limit (DL) of ~20 CFU/mL. Furthermore, the method shows great specificity for target bacteria, and detection procedures could be completed in 15 minutes. With these priorities, this platform has been applied successfully to the detection of MRSA and KPC-2 KP in human urine, saliva, cerebrospinal fluid, and bovine blood. Utilizing different aptamers, this strategy could also be used to monitor other target bacteria with high specificity and sensitivity.