Oxytetracycline (OTC) is a broad-spectrum antibiotic in tetracycline family, which inhibits the growth of various gram positive and gram negative bacteria. OTC is widely used in aquaculture and also in livestock for prevention and treatment of diseases. Since the presence of low levels of residues in food product led to the problem of drug resistance of pathogens in human, it is essential to detect its residue in the food products. Therefore, many countries set the maximum residues limit (MRLs) for oxytetracycline in muscle at 200 μg/kg. The aim of this work was to generate monoclonal antibody against OTC for developing ELISA test kit. OTC was conjugated to bovine serum albumin (BSA), as an immunogen. Ten BALB/c mice were immunized and gave antiserum titers ranging from 1:16,000 to 1:128,000. Cell fusions of splenocytes and myeloma NSI were performed yielding 3 monoclones, 2-4F, 7-3G and 11-11A which produce monoclonal antibody against OTC. Isotyping, sensitivity and cross reactivity of these clones were characterized. The isotype of these clones were IgG₁, IgG₂a and IgG₁ respectively. The sensitivity of these clones were found in terms of 50% of inhibitory concentration (IC50) at 0.19 ± 0.04, 0.56 ± 0.10 and 2.66 ± 1.16 μg/ml respectively and in term of limit of detection (LOD) at 0.08 ± 0.03, 0.20 ± 0.18 and 0.96 ± 1.21 μg/ml respectively. Monoclonal antibody 2-4F shows %cross reactivity, in the range of 27 to 275%, to other antibiotics in TC group whereas MAb 7-3G shows %cross reactivity in the range of 2 to 41%, to TC, DC and RTC and 11-11A showed cross reacted to only DC at 19%. Moreover, these three monoclonal antibodies showed no cross reactivity to all other tested compounds in other groups.
