A rapid screening method for detection of ampicillin residues in dairy milk

The extended use of antibiotics in dairy animals for the growth promotion and disease prevention is directly linked with the development of antimicrobial resistance. This study reports the development of a quick method for the detection of ampicillin residues in dairy milk, using the principle of Lateral Flow Assay (LFA). In this study, hapten against ampicillin was prepared by conjugation with bovine serum albumin. Primary antibodies against this hapten were raised in rabbits and purified. Total protein (IgG) in hyperimmune serum was measured and evaluated by direct ELISA. Gold nanoparticles were conjugated with primary antibodies and impregnated on the conjugate pad of a multi-layered residue detection strip, placed in plastic cassette with clear demarcations of test and control lines on nitrocellulose membrane. The LFA developed using polyclonal antibodies demonstrated the rapid detection of maximum residue limits (MRL) of ampicillin (5 ppb) in milk samples within 8 to 10 min. The kit developed in this study can be used for screening ampicillin residues in milk samples throughout the supply chain, starting from production to consumers' doorstep.