Detection of Listeria monocytogenes based on teicoplanin functionalized magnetic beads combined with fluorescence assay

Abstract Listeria monocytogenes (L. monocytogenes) is a zoonosis pathogen that can cause listeriosis with a high morbidity and mortality. Accordingly, a strategy with high sensitivity and exploitability for detecting L. monocytogenes must be developed. Herein, we introduced a double mediation system based on polyethylene glycol (PEG) and bovine serum albumin (BSA) to prepare teicoplanin (Teic)-functionalized magnetic beads (MBs). This system was then combined with monoclonal antibody-modified quantum dot microspheres (QBs), to develop a rapid and sensitive strategy for detecting L. monocytogenes. Teic, as an antibiotic, mainly bind to Gram-positive bacteria via forming the five-point hydrogen bond between the heptapeptide on its main chain and the terminal D-alanyl-D-alanine (D-Ala-D-Ala) on the cell wall of Gram-positive bacteria. In addition, the antibody guaranteed the specificity for L. monocytogenes detection. The capture efficiency (CE) of MBs-PEG-BSA-Teic for L. monocytogenes at the concentrations ranging from 2.6 × 101 CFU/mL to 2.6 × 104 CFU/mL exceeded 92% in phosphate-buffered saline (PBS) and 89% in the spiked ground beef samples. The limit of detection of the strategy for L. monocytogenes was 2.6 × 101 CFU/mL in both PBS and spiked ground beef samples. Therefore, the proposed strategy is capable of detecting L. monocytogenes with a high specificity and an excellent sensitivity.