Broad-spectrum monoclonal antibody and a sensitive multi-residue indirect competitive enzyme-linked immunosorbent assay for the antibacterial synergists in samples of animal origin

•Molecular modelling was used for hapten design and antibody analysis.•A sensitive and broad-spectrum mAb against 6 antibacterial synergists was obtained.•A mAb-based ic-ELISA was developed for antibacterial synergists in various samples. To monitor the abuse of antibacterial synergists, a hapten, trimethoprim carboxylic derivative (TMPCOOH), was designed by using molecular modelling technology. A broad-spectrum monoclonal antibody (mAb) TMP/2G1 was prepared, for which the IC50 values of trimethoprim, diaveridine, aditoprim, baquiloprim, ormetoprim, and brodimoprim were 0.232, 0.527, 1.479, 4.354, 0.965, and 0.119 µg L−1, respectively. Based on the broad spectrum mAb, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) was developed to determine the residues of antibacterial synergists. The limit of detection regarding the developed ic-ELISA for antibacterial synergists ranged from 0.025 to 1.126 µg L−1 in milk, honey and edible animal tissues. The recoveries ranged from 81.4% to 107.7%, with a coefficient of variation less than 20%. A good correlation (R2 = 0.994) between the ic–ELISA and HPLC–MS/MS showed the reliability of the developed ic-ELISA.